Weird and Wacky Engineering
Comment
Atomic.dave
Hello I too have built a chaney kit c6981 with digital display. It seemed to ...
Max the Magnificent
Great advice -- thanks for this tip
My Geiger counter doesn’t count (sob sob)
Clive Maxfield
4/8/2011 1:10 PM EDT
As you may recall, a couple of weeks ago I penned a blog titled Is that a Geiger counter in your pocket (or are you just happy to see me)? As part of this I mentioned that I would like to own a Geiger counter…
Well, my chum Brian pointed me at the Kits USA website, where they have all sorts of educational do-it-yourself kits, including a bunch of Geiger Counters.
I was immediately attracted to the C-6979 Sensitive Geiger Counter Kit (on the basis that this was the cheapest [grin]). According to the website, this uses a Russian Geiger-Mueller tube and is sensitive to Beta and Gamma rays. As the folks at Kits USA cheerfully say:
Want to know if that orange colored plate that was all the rage in the 60's is radioactive, how about your dad's radium dial watch, or the mantles on your camping lantern – this will tell you! This kit produces the familiar audio clicks and lights up a blue/green LED in response to radioactive sources. Random clicks are even heard from your kit as cosmic rays strike the tube!
Uses a Russian GM tube that was made during the cold war (we test every one for proper operation), various resistors, capacitors, and a special miniature speaker. Operates from one 9V battery (not included). Comes with all parts, PC board, GM Tube and instructions (no case available). Size of PC board 4-5/16" x 1-1/2". Skill Level 2. Requires soldering.
“Ah Ha!” I thought, “I know which end of the soldering iron is the hot one” (it took a while, but I learned over time), so I immediately placed an order. (Actually, on the off-chance you are tempted to purchase one of these kits yourself, I should give you a “heads up” that the folks at Kits USA charge an “arm and a leg” for shipping and handling – seriously, I just checked the invoice and they charged me $26.85, which I think is a bit “naughty” of them.)
Now I have to say that – generally speaking – the instructions that came with the kit are first rate. Even a complete ding-bat like myself should have no trouble assembling one of these. Thus it was that I shortly had the assembled kit sitting on my desk. So with great excitement I connected the battery, turned the power switch to its ON position, the LED lit up, the speaker clicked once, and … nothing else happened.
“Hmmm,” I thought to myself. The thing was that I didn’t have a radiation source to hand. I remember the good old days when wristwatches had glow-in-the-dark numbers based on the use of highly radioactive radium … until the powers-that-be realized that this was not a good idea. But my current wristwatch does not boast this feature [actually it can’t even boast that it keeps accurate time (it gains about 5 minutes a day, so I have to reset it every morning), but it looks good, and I always say that you can’t put a price on “cool” (grin)].
So I went for a wander around the building in which my office is located to see if anyone had a glow-in-the-dark watch. Perhaps not surprisingly, the first person I asked responded by saying “Why do you want one?” When I explained, he told me that a few minutes before he had seen Bruce (the guy who owns the company that owns the building) wandering around carrying a puck of radioactive material (see the photo below).
Yes, I know, I know... before you leap into action and post a clever comment, I am fully aware that there is no battery connected in this photo (you see how well I know you [grin]).
So I hunted Bruce down, and sure enough he had a puck of radioactive cesium that emits beta and gamma radiation in his pocket. Why? I didn’t ask. As the years have gone by I’ve found it makes my life a lot simpler if I don’t inquire too deeply about this sort of thing. So I borrowed Bruce’s puck and held it next to my Geiger counter… still nothing…
Bummer!
When I reported back to Bruce, he did point out that his puck was only mildly radioactive at 5 micro-Sieverts, which really isn’t much in the scheme of things (see the Radiation Chart on the XKCD website). So is this enough to trigger my counter? Who knows?
Now, the instructions that came with the kit do include some trouble-shooting instructions. They start with “Check that you’ve connected the battery,” type directions, but build up to more useful things like “Use a wire to briefly connect the two sides of the GM tube and you should hear a click.” When I do this I do indeed hear a click (hurray) and the LED dims a little, so I think this sort of indicates that things are generally working…
Now it may be that I have a duff GM tube. On the other hand, the creators of the kit do say that they’ve checked all of the tubes. One thing that puzzled me is that the LED is always on. I guess that I would have thought it would be better to have the LED usually off and for it to flash when a radiation event was detected. On the other hand, maybe the kit’s creators thought it would be better to have the LED on so (a) you know that at least something is working and (b) you know when the board is powered up.
But the instructions don’t say whether or not the LED should be on by default, and I’ve not had the time to work it out from the schematic (see below).
I tried calling the makers of the kit – Chaney Electronics – but they didn’t want to talk to me because I hadn’t purchased the kit directly from them. So then I tried calling the folks at Kits USA, but they said that they were selling so many of these kits that they hadn’t actually had a chance to play with them themselves. They did say that they would ask the kit manufacturer for me, but I’ve not heard anything back at the time of this writing.
Of course, one of the things that sparked all of this off in the first place is that I live only about 15 miles from the Browns Ferry Nuclear Plant, which is run by the Tennessee Valley Authority (TVA). So I sent an email to the TVA pointing out that we were actually a match made in heaven – here I am with a Geiger counter but with no radioactive source with which to test and calibrate it – and there they are with a great big nuclear power plant with nothing better to do than generate a lot of electricity. I also mentioned that I would be more than happy to drive over there so that we could use my Geiger counter to make sure that everything was as it should be at their end. Sad to relate, I haven’t heard back from them thus far, but I live in hopes…
In the meantime, I sent an email to my friend Arthur in England. Arthur is one of the world’s foremost experts in Cosmic Rays, but he decided that it would be more fun to run a small farm with his dad, so most of the messages I see from him these days focus on things like bee hives and strange problems with cows. Anyway, Arthur responded as follows:
Hi Max, you should get some clicks from natural back ground radiation, not very many, but say every few minutes. The tube you have looks to be gamma and beta sensitive, but probably not sensitive to muons, which arrive at earth at around 0.1/cm**2/s. The case is also too thick to allow alpha particles into it.
The source you have is likely 5 micro-Sieverts and should be 'see-able' with your tube. But I have a friend in Oxford who built a Maplin kit and we couldn't get any response out of it, either with an x-ray source or in front of a CRT tube, source of x-rays, in a big TV.
The tubes contain gas which can leak out so that might be a problem as by shorting out the tube you are verifying that the click circuit is working and likely the HV too. I have known them fail due to HV leaking from the tube across the PCB. The board has to be very clean, free of any flux etc. Often commercial ones are attached with Teflon spacers to minimize charge leakage.
Does the supplier give any info on what the back ground rate is with the device? Something else might come to mind but for the moment I can't think of any other suggestions. Regards – Arthur
I’ve also received a few suggestions via email as follows:
Don writes: Hi Max, I enjoy your musings in your articles. Try an ionizing smoke detector. It should contain a small amount of Americium (element 95 in atomic table). The exact value should be called out inside the cover of the detector. Or you could check someone’s basement for radon gas!
Edith says: Hi Clive, a classic radiation source is a lamp mantle. They are little nets that are hung in a camp lantern over a kerosene flame to help create more light. If they still make them, they should be in a good hunting type outdoor equipment store. Or an old glowy watch face, or a classic red piece of Fiestaware pottery (the uranium in the glaze was a bonus). Otherwise you could just hold it against your thyroid and see if the static sounds louder…
Rolf commented: Hi Max, you could try to find an old watch or clock at an antique shop that has a radium dial.
James said: Hey Max,your comment about DIY Geiger counters reminded me of a demonstration that I saw as a high school student... Back in the early '90s, Atomic Energy Canada hired a spokesman that looked and talked like the old scientist from the 'Back to the Future' movies. His job was to spread the love of all things nuclear. As part of his seminar he showed us that radiation is all around us. The one source that was the most surprising was a wick from a Coleman lantern. As purchased off the shelf from the local hardware store, these little items (aka scamps) made the Geiger counter sing loudly. High school was a long time ago so I don't know if Coleman still uses nuclear powered wicks, but it was unexpected and impressive.
And Rob noted: Hi Max, there are several sources you can use. My counter (old Civil Defense version) from the 60s had a sample on the side. But I found some others.
All good suggestions – not the least that the Home Depot stocks a lot of these items like granite and smoke detectors (maybe even Coleman mantels). On the other hand, I’m not sure what they would think of my skulking up and down the aisles with my home-made Geiger counter in my hands – especially if it started clicking furiously (I dream of the day, so long as I'm the instigator of its leaping into action).
This evening I will take my Geiger counter home and hold it near to the smoke detector in my house … but even if it still doesn’t work, that may not mean there’s anything wrong with it – it may just mean that my smoke detector doesn’t use a radioactive source to detect smoke.
If all else fails, I might do it to go down to an old antique (junk) shop to see if I can find an old clock with glow-in-the-dark numbers on it…
Well, my chum Brian pointed me at the Kits USA website, where they have all sorts of educational do-it-yourself kits, including a bunch of Geiger Counters.
I was immediately attracted to the C-6979 Sensitive Geiger Counter Kit (on the basis that this was the cheapest [grin]). According to the website, this uses a Russian Geiger-Mueller tube and is sensitive to Beta and Gamma rays. As the folks at Kits USA cheerfully say:
Want to know if that orange colored plate that was all the rage in the 60's is radioactive, how about your dad's radium dial watch, or the mantles on your camping lantern – this will tell you! This kit produces the familiar audio clicks and lights up a blue/green LED in response to radioactive sources. Random clicks are even heard from your kit as cosmic rays strike the tube!
Uses a Russian GM tube that was made during the cold war (we test every one for proper operation), various resistors, capacitors, and a special miniature speaker. Operates from one 9V battery (not included). Comes with all parts, PC board, GM Tube and instructions (no case available). Size of PC board 4-5/16" x 1-1/2". Skill Level 2. Requires soldering.
“Ah Ha!” I thought, “I know which end of the soldering iron is the hot one” (it took a while, but I learned over time), so I immediately placed an order. (Actually, on the off-chance you are tempted to purchase one of these kits yourself, I should give you a “heads up” that the folks at Kits USA charge an “arm and a leg” for shipping and handling – seriously, I just checked the invoice and they charged me $26.85, which I think is a bit “naughty” of them.)
I was jolly excited when my kit arrived
Now I have to say that – generally speaking – the instructions that came with the kit are first rate. Even a complete ding-bat like myself should have no trouble assembling one of these. Thus it was that I shortly had the assembled kit sitting on my desk. So with great excitement I connected the battery, turned the power switch to its ON position, the LED lit up, the speaker clicked once, and … nothing else happened.
“Hmmm,” I thought to myself. The thing was that I didn’t have a radiation source to hand. I remember the good old days when wristwatches had glow-in-the-dark numbers based on the use of highly radioactive radium … until the powers-that-be realized that this was not a good idea. But my current wristwatch does not boast this feature [actually it can’t even boast that it keeps accurate time (it gains about 5 minutes a day, so I have to reset it every morning), but it looks good, and I always say that you can’t put a price on “cool” (grin)].
So I went for a wander around the building in which my office is located to see if anyone had a glow-in-the-dark watch. Perhaps not surprisingly, the first person I asked responded by saying “Why do you want one?” When I explained, he told me that a few minutes before he had seen Bruce (the guy who owns the company that owns the building) wandering around carrying a puck of radioactive material (see the photo below).
My assembled kit and the puck of radioactive material
Yes, I know, I know... before you leap into action and post a clever comment, I am fully aware that there is no battery connected in this photo (you see how well I know you [grin]).
So I hunted Bruce down, and sure enough he had a puck of radioactive cesium that emits beta and gamma radiation in his pocket. Why? I didn’t ask. As the years have gone by I’ve found it makes my life a lot simpler if I don’t inquire too deeply about this sort of thing. So I borrowed Bruce’s puck and held it next to my Geiger counter… still nothing…
Bummer!
When I reported back to Bruce, he did point out that his puck was only mildly radioactive at 5 micro-Sieverts, which really isn’t much in the scheme of things (see the Radiation Chart on the XKCD website). So is this enough to trigger my counter? Who knows?
Now, the instructions that came with the kit do include some trouble-shooting instructions. They start with “Check that you’ve connected the battery,” type directions, but build up to more useful things like “Use a wire to briefly connect the two sides of the GM tube and you should hear a click.” When I do this I do indeed hear a click (hurray) and the LED dims a little, so I think this sort of indicates that things are generally working…
Now it may be that I have a duff GM tube. On the other hand, the creators of the kit do say that they’ve checked all of the tubes. One thing that puzzled me is that the LED is always on. I guess that I would have thought it would be better to have the LED usually off and for it to flash when a radiation event was detected. On the other hand, maybe the kit’s creators thought it would be better to have the LED on so (a) you know that at least something is working and (b) you know when the board is powered up.
But the instructions don’t say whether or not the LED should be on by default, and I’ve not had the time to work it out from the schematic (see below).
I tried calling the makers of the kit – Chaney Electronics – but they didn’t want to talk to me because I hadn’t purchased the kit directly from them. So then I tried calling the folks at Kits USA, but they said that they were selling so many of these kits that they hadn’t actually had a chance to play with them themselves. They did say that they would ask the kit manufacturer for me, but I’ve not heard anything back at the time of this writing.
Of course, one of the things that sparked all of this off in the first place is that I live only about 15 miles from the Browns Ferry Nuclear Plant, which is run by the Tennessee Valley Authority (TVA). So I sent an email to the TVA pointing out that we were actually a match made in heaven – here I am with a Geiger counter but with no radioactive source with which to test and calibrate it – and there they are with a great big nuclear power plant with nothing better to do than generate a lot of electricity. I also mentioned that I would be more than happy to drive over there so that we could use my Geiger counter to make sure that everything was as it should be at their end. Sad to relate, I haven’t heard back from them thus far, but I live in hopes…
In the meantime, I sent an email to my friend Arthur in England. Arthur is one of the world’s foremost experts in Cosmic Rays, but he decided that it would be more fun to run a small farm with his dad, so most of the messages I see from him these days focus on things like bee hives and strange problems with cows. Anyway, Arthur responded as follows:
Hi Max, you should get some clicks from natural back ground radiation, not very many, but say every few minutes. The tube you have looks to be gamma and beta sensitive, but probably not sensitive to muons, which arrive at earth at around 0.1/cm**2/s. The case is also too thick to allow alpha particles into it.
The source you have is likely 5 micro-Sieverts and should be 'see-able' with your tube. But I have a friend in Oxford who built a Maplin kit and we couldn't get any response out of it, either with an x-ray source or in front of a CRT tube, source of x-rays, in a big TV.
The tubes contain gas which can leak out so that might be a problem as by shorting out the tube you are verifying that the click circuit is working and likely the HV too. I have known them fail due to HV leaking from the tube across the PCB. The board has to be very clean, free of any flux etc. Often commercial ones are attached with Teflon spacers to minimize charge leakage.
Does the supplier give any info on what the back ground rate is with the device? Something else might come to mind but for the moment I can't think of any other suggestions. Regards – Arthur
I’ve also received a few suggestions via email as follows:
Don writes: Hi Max, I enjoy your musings in your articles. Try an ionizing smoke detector. It should contain a small amount of Americium (element 95 in atomic table). The exact value should be called out inside the cover of the detector. Or you could check someone’s basement for radon gas!
Edith says: Hi Clive, a classic radiation source is a lamp mantle. They are little nets that are hung in a camp lantern over a kerosene flame to help create more light. If they still make them, they should be in a good hunting type outdoor equipment store. Or an old glowy watch face, or a classic red piece of Fiestaware pottery (the uranium in the glaze was a bonus). Otherwise you could just hold it against your thyroid and see if the static sounds louder…
Rolf commented: Hi Max, you could try to find an old watch or clock at an antique shop that has a radium dial.
James said: Hey Max,your comment about DIY Geiger counters reminded me of a demonstration that I saw as a high school student... Back in the early '90s, Atomic Energy Canada hired a spokesman that looked and talked like the old scientist from the 'Back to the Future' movies. His job was to spread the love of all things nuclear. As part of his seminar he showed us that radiation is all around us. The one source that was the most surprising was a wick from a Coleman lantern. As purchased off the shelf from the local hardware store, these little items (aka scamps) made the Geiger counter sing loudly. High school was a long time ago so I don't know if Coleman still uses nuclear powered wicks, but it was unexpected and impressive.
And Rob noted: Hi Max, there are several sources you can use. My counter (old Civil Defense version) from the 60s had a sample on the side. But I found some others.
- Standard smoke detector which has Americium (a soft radioactive silvery-white metal) which emits alpha particles which smoke will block hence setting off the alarm (very short version).
- Coleman mantels for gas camping lanterns. Treated with Thorium will set off you detector. Some off brands don’t seem to be treated.
- Old analog wrist watches have Radium painted on the hands (and dots).
- You can also go to the doctor and have them do a stress test on you and when they shoot you up with Barium you can play with yourself for several days (…never mind) as it has a half-life of (I was told so don’t quote me) about 36 hours. Of course your body passes it in about 2-3 days.
- And one I have yet to find but I am told that some are quite hot, granite counter tops. I have been meaning to take my detector to Home Depot but have not had a chance yet.
All good suggestions – not the least that the Home Depot stocks a lot of these items like granite and smoke detectors (maybe even Coleman mantels). On the other hand, I’m not sure what they would think of my skulking up and down the aisles with my home-made Geiger counter in my hands – especially if it started clicking furiously (I dream of the day, so long as I'm the instigator of its leaping into action).
This evening I will take my Geiger counter home and hold it near to the smoke detector in my house … but even if it still doesn’t work, that may not mean there’s anything wrong with it – it may just mean that my smoke detector doesn’t use a radioactive source to detect smoke.
If all else fails, I might do it to go down to an old antique (junk) shop to see if I can find an old clock with glow-in-the-dark numbers on it…
|
|
|
|
|
Navigate to related information
Max the Magnificent
4/8/2011 1:31 PM EDT
Any suggestions (preferably as comments here) will be very gratefully received...
Sign in to Reply
spyderjacks
4/14/2011 8:23 AM EDT
Max:
I built the same kit and it clicks away (and LED lights), every couple of seconds. I would check your solder traces for shorts. Then check that you didn't confuse the transistors. Other than that, it looks like you got all the parts in the right place.
Sign in to Reply
Max the Magnificent
4/14/2011 10:06 AM EDT
I want mine to click (sob sob)
Sign in to Reply
toddkrein
4/14/2011 12:30 PM EDT
Max, I bought the same kit, and I have exactly the same problem. Poking around with a scope didn't enlighten me much, so I can't wait to try of the advice given here.
Sign in to Reply
stephen.melnick
4/14/2011 8:47 AM EDT
If the ground terminal of the tube is connected to the negative battery terminal, things make a lot more sense. The tube probably has enough capacitance to do the smoothing. When it triggers , C3 feeds the pulse to the LED and R4 sends it to the speaker. Did your kit possibly come with a bad board that was missing a connection?
Sign in to Reply
Max the Magnificent
4/14/2011 10:05 AM EDT
Nope -- there is no ground connection to the negative side of the tube
Sign in to Reply
pchow
4/24/2011 2:52 AM EDT
Hi Max,
I have the digital display version of the kit and encountered the same issue as you. After debugging the kit for several weeks, it was determined that changes to the design was necessary to get it working. I have documented my mods here:
https://picasaweb.google.com/101778441575121007208/Geiger_chaney6981Modified#
In summary: a 20 pF cap was placed between the diode and the other side of the tube, the tube's anode resistor value is too small, added a resistor between E-B of the Darlington transistor. I also completely removed the speaker circuit.
I don't know if others will concur with my modifications, but I hope my suggestions will help get your kit working.
Best Regards,
Peter
Sign in to Reply
mebbin
11/2/2011 8:15 PM EDT
I have the same kit. I use some extra holes and two pcb fuse clips to connect the tube way better than the wire link solution proposed in the instructions.
Sign in to Reply
Max the Magnificent
11/3/2011 11:04 AM EDT
Great advice -- thanks for this tip
Sign in to Reply
David Ashton
4/8/2011 8:54 PM EDT
Hi Max
If your led is on all the time then either C3 or Q3 is shorted (possibly on the PC board (lose marks for bad soldering!) or maybe one of them is just bad. You could also check the voltage actoss the tube - you should have a good few hundred volts across the ends (use a DMM as that voltage is from a very high impedance thru R3). If you don't, there's something wrong with the VH inverter areound the 555 / Q1 / T1.
One thing that strikes me here....off the secondary of the inverter transformer T1, you have a rectifier D1 and then R3 supplying the GM tube, but there is no smoothing for the HV DC thus produced. You could try putting a 0,1 Uf 1000v Capacitor (not the easiest thing to find) from the cathode of D1 to the other side of the T1 HV winding. Without this, you'll get pulses of HV instead of a nice smooth DC. The pulses having a large AC component, that might be getting thu C3 and turning your LED on. I'll send you a modified circuit diagram via email. Your speaker would also be activated by these pulses, but probably at a frequency too high to hear. Poking around with a scope might help. Just noticed also that the LED and Speaker circuits are on the 9v side and the GM tube HV circuit is really totally isolated from the 9v circuit. I'd also try connecting the bottom end of T1 secondary to the negative of the 9V.
Finally, it's total "caca de toro" (lovely expression I learned from another post, meaning BS) that the makers of the kit won't help you just because you didn't buy it from them. They still sold it wholesale to Kits USA, didn't they? Don't you have some kind of consumer watchdog there you could go to about this?
Sign in to Reply
zeeglen
4/8/2011 11:19 PM EDT
Something strange in the schematic, the negative of the GM tube is not DC referenced to any other point in the circuit. Is this a schematic typo or is the circuit actually wired this way?
Sign in to Reply
David Ashton
4/9/2011 4:26 AM EDT
I noticed that too Glen, there would be a bit of capacitive coupling thru the transformer but I'm not sure if that would work, even for the pulses that you'd get from the tube...
Sign in to Reply
zeeglen
4/9/2011 7:05 AM EDT
Interwinding capacitance would provide the DC isolation needed for the Q2 audio section, so maybe this actually is intentional.
Sign in to Reply
Max the Magnificent
4/11/2011 10:52 AM EDT
Nope -- it really is wired this way
Sign in to Reply
zeeglen
4/9/2011 7:12 AM EDT
Max,
When I worked at Heathkit one of the most common problems was transistors installed with leads interchanged, or transistor types swapped because their packages looked identical and part numbers hard to see.
You might also want to look for a logo stamped on the transistors and verify the lead arrangement with the online data sheet. It does happen that parts substitution gets done with nobody noticing that the new vendor's part has a different pinout.
It might also help to inform Chaney Electronics that you are a technical writer and have broadcast their lack of assistance to the entire world.
Sign in to Reply
Max the Magnificent
4/11/2011 10:55 AM EDT
I'm reasonably confident about the transistors -- the downside it that now they are in I can't read the markings (my eyes aren't what they used to be) -- but I'll see if I can get someone with younger eyes to check for me.
Sign in to Reply
David Ashton
4/9/2011 8:21 PM EDT
Glen - I reckon the lack of HV smoothing is the main culprit, that would give a large AC component on the GM tube which would (a) light the LED (b) get onto the speaker (though you wouldn't hear it) and (c) stop it working normally. C3 might give a bit of smoothing but that's not its primary function.
Ref informing Cheney - good idea! Companies like this deserve all the negative publicity that they can get!
Sign in to Reply
zeeglen
4/10/2011 9:03 AM EDT
Yes, there should be HV smoothing. But if there is a design flaw then none would work.
Sign in to Reply
Max the Magnificent
4/11/2011 10:53 AM EDT
They do sell a lot of these as educational kits, so you have to assume that the basic circuit is good.
Sign in to Reply
David Ashton
4/12/2011 9:42 AM EDT
Rule No. 1. Never assume....
Sign in to Reply
Tom.Clarke_#1
4/14/2011 4:01 AM EDT
You can just use a £5 ionization smoke alarm as your radioactive source.
Sign in to Reply
FlyTyer1
4/14/2011 8:17 AM EDT
Try removing cap C3. If the LED goes out, it's the ac problem. If the LED stays on, the transistor is in wrong or just bad.
Sign in to Reply
Hernando.Garcia
4/14/2011 10:28 AM EDT
The circuit design is too basic and unhappily it is an open loop transformer boost circuit, to solve the problem measure the DC voltage to be in the 540 Vdc range, use a 10 megohms meter or better. The next step is the amplifier ( a fet device) that has a poor gain the way it was designed and may be a possible cause -- short circuit the Geiger tube ( I normally would use the same value resistor that is in series with the Geiger counter instead of the shorting wire ) If you hear the clicks then the Geiger tube may have leaked to death.
The LED pulses sporadically with the background geiger tube detecing ambient radiation and should not be ON, unless the Geiger counting radiation rate faster than the human can differentiate the pulses and the audio squeaks should be heard -- so if the vdc is within Geiger Vrange and NO clicks but clicks when shorting the tube = BAD Geiger tube.
The Kit as designed it is a very bad design done by somebody with very basic electronic knowledge .
Good Luck
Sign in to Reply
tsmith35
4/14/2011 11:35 PM EDT
Chaney has a video of the kit in operation on their site: http://www.electronickitsbychaneyelectronics.com/prodinfo.asp?number=C6979
The LED blinks once per click.
Sign in to Reply
Max the Magnificent
4/15/2011 11:08 AM EDT
That looks so cool!!! That's what I want mine to do!!!
Sign in to Reply
Max the Magnificent
4/15/2011 11:10 AM EDT
So here's the current state of play -- electronics expert David Ashton (see the comments above) has kindly offered to take a look at it for me -- I shipped it off to David (who lives in Australia) yesterday (the postage was only $4.80, which I thought was an amazingly good deal).
I will report further in a future blog...
Sign in to Reply
David Ashton
4/16/2011 6:00 PM EDT
That's called "putting Max's money (all $4.80 of it) where my mouth is". I'm not so sure about the expert bit, but it'll be interesting to see what the problem is. Watch this space....
Sign in to Reply
Stargzer
4/18/2011 2:13 PM EDT
When I was a kid in grade school (1960s) there was a book series, "A Boy's First (followed by Second (tubes--valves for David :-) ) and Third (transistors)) Book of Radio and Electronics. I think it was the Second book that had a Geiger Counter in it. It used a push-button switch to close-and-open the primary of the transformer to the high voltage needed for the tube. It looks like they're using the 555 and a transistor to save you from having to push the button 100 or so times to charge the tube.
As the book described the tube, it was like a diode vacuum tube (maybe with a gas of some sort in it, but not normal air), and when a charged particle went through the tube it caused it to conduct (short from anode to cathode).
Shorting produces a click, but as others have suggested, make sure you're getting something much greater than 9V across the tube.
It looks to me like the LED should only blink when there's a click.
If the kit is wired correctly and the LED is on continuously, then Max may be being exposed to enough radioactivity to cause the tube to be permanently shorted, causing no click and the LED to be permanently on. If Max survives this, he can probably make a lot of money working on the East coast of Northern Japan these days ...
;-)
Sign in to Reply
alarict
4/20/2011 12:54 AM EDT
Hello EE Posters...
I have the same kit, a different problem...
I found the C6979 online and eagerly purchased it last week. It arrived, I checked off the contents list, everything was present and correct (so far). I then started to assemble and installed the last resistor, R6, however the parts layout diagram had a resistor 7. Looking at my board, it has space for R7, also the circuit diagram has R7. The three places omitting R7 were the photograph, the parts list and most importantly the kit. R7 sits between the LED and the switch. I am contacting Chaney to see what I should use...
Does anyone has any advice on what size resistor I should install? If Chaney replies or I get hold of them I will post.
Sign in to Reply
David Ashton
4/20/2011 4:45 AM EDT
Well spotted!! I hadn't even noticed that. It'll be just a current limit resistor for the LED - anything around 470 ohms should work. I have not yet recieved Max's kit - his LED comes on (all the time) so he must have a resistor there, else the LED would blow when Q3 turns on..... I'll update when I have seen Max's kit.
Sign in to Reply
zeeglen
4/20/2011 4:31 PM EDT
Maybe the LED is a newer substitute with an internal resistor? Also same lack of current limit for the speaker, unless speaker is high DC resistance.
On lack of HV smoothing, with absolutely no load (GM tube not conducting) it could be that stray capacitance is all that is needed for the smoothing. But if anything draws current, such as D1 leakage or conductive solder flux on the pcb, then ripple can result.
Will be interesting to see what you find. Hard to comprehend how the manufacturer does not offer repair support.
Sign in to Reply
spyderjacks
4/20/2011 3:00 PM EDT
I have a working C6979, with no R7 listed or in the schematic. My doc is "Rev 03/30/10LW". So I'm wondering if some evolution in the schematic is not in agreement in the kit contents? The schematic indicated here is the one that I followed.
Sign in to Reply
Max the Magnificent
4/20/2011 3:03 PM EDT
My counter (with the kit documentation) is en-route to David in Australia -- when it gets there maybe he can check the doc rev number...
Sign in to Reply
alarict
4/20/2011 10:20 PM EDT
David - thank you, 470 ohms later its clicking away nicely (but reassuringly intermittently).
My C6979 instructions show rev number 04/11/11/LW. I have loaded images from the assembly instructions here (the red highlighting for R7 is of course mine): http://i1098.photobucket.com/albums/g369/alarict/GC/3diagrams.gif
The LED flashes when the speaker clicks. I doubt the LED has an internal resistor as it looks the same as the ones I order in bulk to make LED arrays and they need the external stabilizing resistor.
Sign in to Reply
David Ashton
4/21/2011 5:37 AM EDT
Glad that's now good...but that resistor should not have stopped it clicking (of maybe you didn't try it till you got the resistor in??) I still have not got Max's one (maybe that is why the shipping was so cheap, it's actually coming by ship... :-) but it will be interesting to compare yours with his.
Glen, ref your comment about no resistor in the speaker line either. There's only AC coupling to the speaker circuit due to the lack of a DC return previously noticed...so even if the speaker was quite low impedance it would only ever get clicks.
I wait with bated breath to get into Max's kit....
Sign in to Reply
Max the Magnificent
4/21/2011 10:28 AM EDT
Now I wish I had mine in front of me so I could check for that resistor -- I can't wait for my kit to arrive with David ... come on post office!!!
Sign in to Reply
finevlad
4/25/2011 6:15 PM EDT
What I see in this digram is that one of the electrodes is connected to the middle part of the tube. While this type need to use both ends connectors. Also one of the ends is marked "+".
Sign in to Reply
Max the Magnificent
4/25/2011 6:29 PM EDT
As I recall, the end marked + is electrically isolated from the rest of the tube -- the middle of the tube and the other end (the end opposite the end market +) are all electrically connected together, so it doesn't matter if you connect to the middle...
Sign in to Reply
ArekZ
4/21/2011 5:20 AM EDT
Is it possible that the Russian made tube does not work in America?! 8))))))
When I was in a primary school, in south western Poland, just after Tchernobyl, I built one Geiger counter. The tube looked different (one end was sensitive) but it did work. I tried various materials. The background noise was about 10 clicks per min and with an old watch it was going crazy. A few years later I tried it in the UK and the background radioactivity was the same.
My guess is that in this case the problem is with the tube - got damaged during transporation?
Sign in to Reply
Max the Magnificent
4/21/2011 10:18 AM EDT
The folks who supply the kit say that they check all of the tubes first -- and it arrived well-packaged. I think the fact that the LED is continuously ON when it shouldn't be is a givaway that something is wrong with the circuit...
Sign in to Reply
spyderjacks
4/21/2011 4:01 PM EDT
You can make the LED stay lighted by grabbing the underside of the board with your hand. So I would suspect that you have a short somewhere.
Sign in to Reply
Max the Magnificent
4/21/2011 4:19 PM EDT
I'm not saying there isn't one -- but you can bet that I looked for one with great attention ... so if I missed it I will have to take myself outside and give myself a sound spanking (grin)
Sign in to Reply
alarict
4/21/2011 2:31 PM EDT
ArekZ - I'm counting 10-15 clicks per minute in CA.
Dave - Long story but I didn't try the circuit before installing the resistor...
Sign in to Reply
finevlad
4/21/2011 7:07 AM EDT
This tube has 360..440V operation range - you need to check that you are in the range.
Sign in to Reply
finevlad
4/21/2011 7:20 AM EDT
Here you can find alternative schematics with the same sensor tube type:
http://mulder.ucoz.ru/_bl/0/58019918.gif
http://lavr30.narod.ru/htmsch/auto/dozim2/p1.gif
Sign in to Reply
Max the Magnificent
4/21/2011 10:18 AM EDT
Great -- thanks for the heads-up -- Max
Sign in to Reply
David Ashton
4/21/2011 9:37 PM EDT
The notable thing about both those scematics is that they both have a capacitor (2200 PF) to smooth the HV for the tube (I recommended something considerably higher, but same theory).
Ref the comment about grabbing the underside of the board. With 400+ volts flying around under there I wouldn't be too keen to do that... $-(
Sign in to Reply
Max the Magnificent
4/22/2011 10:23 AM EDT
If you want to protect your fingers, just touch it with your tongue :-)
Sign in to Reply
spyderjacks
4/23/2011 1:40 PM EDT
Dude. The instructions specifically caution against putting any components in your mouth. But I think you can get the same effect by putting the battery on your tongue. Those contacts are plated !!! ;-)
Sign in to Reply
spyderjacks
4/22/2011 5:06 PM EDT
It's not the voltage - it's the current! And the current just ain't that much. Static electricity will tag you 20,000 volts - still no reported injuries ;-)
(semiconductors excepted, of course)
Sign in to Reply
shiverman
4/22/2011 5:19 PM EDT
I'm having the same problem with my C6986 Geiger counter kit!
Blue light stays ON, no clicks. :(
I took out Q3 and I think the light was off.
Thing is I bought TWO kits and they do exactly the same thing!
The only thing I'm not sure of is Resistors R1-R6, I had to use an online calculator to find out they're value's as the color codes are not included.
Also I'm not sure If I have to SOLDER the crimped wire on the geiger tube at the circuit board or not.
I tripple checked all Caps and IC's, they're in the right way, not sure what else it could be.
Double checked all solder points and redid somewhat questionable one's.
Please post results asap!
thanks for this blog!
Sign in to Reply
spyderjacks
4/23/2011 1:38 PM EDT
Don't solder the crimped connector. I got about 60% of the circumference in mechanical contact.
I use my multimeter to checks the resistor and capacitor values. I can barely see the strips and printing anyway.
I started documenting all the significant voltages and signals but now my Geiger has stopped counting - so I'm now part of the debug pool. I noticed that the LED was faintly lit, maybe due to a leaky transistor. We'll see what turns up.
Sign in to Reply
gwasik
4/23/2011 9:53 PM EDT
I just built one of the C6979 units w/o any changes to the kit design. I'm getting about 16-25 counts per minute of background here near Boston. I think that is a bit high perhaps. One thing I noticed is that when I placed the pcb on a blank sheet of paper, the led stayed on, and no counts occurred. You might want to put some standoffs on the board.
http://www.youtube.com/watch?v=Pq-bvCgozu4
Sign in to Reply
David Ashton
4/24/2011 7:17 AM EDT
Sounds like I'll have my work cut out fixing these things. Max's is still on the way - and I won't get it before Wednesday due to public holidays here in Aussie. But I will report back asap (To Max first, 'cos its his kit :-)
Sign in to Reply
pchow
4/25/2011 1:48 PM EDT
Hi Max, David, et al.,
The main problem with this kit design seems to be that the high voltage generated by the transformer and diode is constantly be being discharged or drained off somehow at the G-M tube anode. Under these conditions, the 555 pulses pass through C3, resulting in LED glow and a 250 Hz speaker buzz from the 555.
I posted a comment in the blog earlier (and out of sequence - so scroll up), which has a URL to my solution.
The kit also seems to be humidity sensitive, i.e. if you blow on the transformer or Darlington, the LED will glow brighter! It's probably some kind of high voltage leakage under humid conditions?
- Peter
Sign in to Reply
Max the Magnificent
4/25/2011 2:18 PM EDT
So when David gets it working (as I have no doubt he will), I will have to live in hope that, should a disaster occur at the nearby nuclear plant, it occurs on a day in which the humidity is low ... hmmm, maybe I should have opted for a slightly more expensive kit...
Sign in to Reply
pchow
4/25/2011 2:56 PM EDT
The humidity observation may have resolved itself with the mods I made. Although it might be better to buy a different more expensive kit, but I was bent on salvaging my $130 project. These kits can be fixed with some simple changes. And for those who were lucky enough to get it working the first time, it still be might be better to make some mods to make it more reliable. We'll see what fix David comes up with.
- Peter
Sign in to Reply
Max the Magnificent
4/25/2011 2:58 PM EDT
I have a lot of faith in David -- he's worth every penny I'm not paying him (grin)
Sign in to Reply
finevlad
4/26/2011 10:47 AM EDT
This weekend I've assembled the voltage supply according to maxim app note "Application Note 3757: www.maxim-ic.com/an3757". Set the output as 400V and connected the same tube. Only added the transistor and buzzer and all the geiger system start clicking! No transformers, very reliable. And consume 40..50uA with background levels. So from 2xCR2032 it would last half a year.
Sign in to Reply
spyderjacks
4/26/2011 6:23 PM EDT
That app note looks promising. Do you have any picture/diagram of your board layout? I'm hoping not to re-invent that wheel. I'm thinking of putting it on an Arduino shield.
While I had a working Geiger counter kit, I was measuring signals and voltages last Saturday. Kit died before I finished - so I spent the rest of the session over-documenting the debug process. It's not complete but it is at least a start for the other folks to chase down their 'dead kit' situation. https://docs.google.com/document/d/1wU7R8qqOO5dKBUsYcJwZcCG7v5toF9Nrvf_vXr8PDxg/edit?hl=en&authkey=CN693pwJ
I think the problem is Q3 but I will not get more parts before next week.
Sign in to Reply
finevlad
4/27/2011 5:27 AM EDT
Hi, upload my schematics to your google docs. you can add or share it if you want. It shows parts used(that I had at the moment) and results obtained. Was doing this on the breadboard - photos later.
Sign in to Reply
finevlad
4/27/2011 5:32 AM EDT
https://docs.google.com/document/d/1PvTMktgIpX7SRKi908HNJHlxlbPPMWLiNzC6i07HYv0/edit?hl=en_GB&authkey=CMbSxsEM
Sign in to Reply
David Ashton
4/27/2011 3:52 AM EDT
I like that...nice regulation of the HV independent of battery voltage. Though from what I know Geiger tubes are not toooo finicky about the voltage. Still not got Max's kit, so I'm still waiting too...
Sign in to Reply
spyderjacks
4/27/2011 9:50 AM EDT
Looks good - thanks.
I'm thinking about the optimal layout... here is a picture of a Velleman kit (discontinued) that looks to be the same ladder-multiplier feature.
https://docs.google.com/document/d/1fyns9vdO29kZlYcldBxjcVBHGWwrLKZkd100xgPVMLo/edit?hl=en&authkey=CMmV9_4P
Sign in to Reply
finevlad
4/27/2011 2:37 PM EDT
here are pictures of my device
https://docs.google.com/leaf?id=0B2Ix98OaeZCwYmNkZTViMTYtMzg0OS00ZTQwLTk1MzAtY2JkZDliZWZmNTE3&hl=en_GB&authkey=CLPGvvAB
https://docs.google.com/leaf?id=0B2Ix98OaeZCwNGY5NzYwMWItMDViMi00NmU0LWFiYzYtNTE0ZjIwOWIzMDJm&hl=en_GB&authkey=CP-AprAE
https://docs.google.com/leaf?id=0B2Ix98OaeZCwNzY1YWFhZGItM2RmNi00NjViLThjY2ItNjFhMDdiZWI4MzVk&hl=en_GB&authkey=CIGGxbQH
https://docs.google.com/leaf?id=0B2Ix98OaeZCwZThjNjY3ZWYtMWJkYS00M2NlLWE0MDEtZGE4MTQ4ZjMyMDYz&hl=en_GB&authkey=CMfGsqYE
Sign in to Reply
gwasik
4/27/2011 8:40 PM EDT
Just a note. My C6979failed to work yesterday- I attributed it to humidity. The LED was on and 200 Hz buzz from the speaker. Today is a bit dryer and its back ticking away... I will try Peter's mods.
Here is it's response to a smoke detector ionizer - AM241 which supposedly only gives off Alpha and small amounts of gamma.
http://www.youtube.com/watch?v=pMAOBdJKMYU
Sign in to Reply
pchow
4/28/2011 1:45 AM EDT
Maybe I should clarify my previous statement on humidity being resolved with my mods - it's more like it's less sensitive. Also, David might be correct in using a larger cap used between the diode cathode and tube "Gnd" (i.e. > 2200 pF) - I'm currently using 20 pF, and I'll try a 4700 pF tomorrow. - Peter
Sign in to Reply
pchow
4/29/2011 1:50 AM EDT
I replaced the said 20 pF capacitor that I had previously with a 4700 pF (4.7 nF) cap. The circuit works better: the digital readout (on the C6981 kit) does not double count anymore during the first minute(s) of operation. And blowing on the transformer (introducing humidity) does not cause LED glow, but might cause the LED to blink faintly or not at all.
So, this new "diode cap" value is a better choice.
I think a glowing LED means that the high voltage at capacitor C3 is experiencing voltage ripples generated by the 555 charge pulses. This implies that the "diode cap" is not large enough to smooth out the high voltage ripples. I do not have a high voltage oscilloscope to confirm this.
I just wonder in how this kit will operate during the humid East Coast summers, verses the dry California one?
- Peter
Sign in to Reply
shiverman
4/27/2011 9:06 PM EDT
I'm going to pull my face off any minute this C6986 kit has consumed my ENTIRE DAY today and on and off on the weekend.
And accomplished NOTHING.
I spent $250 on TWO of these kits I'm really PISSED that something this substandard is even sold at these prices!
I also found they are short one 4.5meg resistor on BOTH KITS and have only about a 1 Meg or something instead.
Also one of my seats for IC4 had a PIN MISSING in it.
Only 1 was working for a WHILE with the light constantly blinking.... now it's dead for no apparent reason.
The Geiger tubes are good, chips were all good the last time I checked this morning, all resistors checked with my volt meter.
I expected MUCH MORE for this price, nothing but hassle with 1 of 2 working for a only short time.
I'm really hoping a fix is found for these as currently I'm OUT $265 !!
:(
Sign in to Reply
shiverman
4/29/2011 1:29 PM EDT
I just changed C4-7 as well as the Darlington Transistor, no difference.
Still cycling odd numbers , light staying on etc.
I sent back to Electronic Goldmine for repair as they don't refund. :(
I hope it doesn't cost me more as I could have just bought finished kits.
I strongly advise anyone interested to spend the extra bit for a completed kit.
Sign in to Reply
Whereswally
5/1/2011 5:41 AM EDT
I have a kit from USA, it is the C6979 REv 04/12/11LW
It worked for about 4 hours. Just long enough to interface to a PicAxe18X chip. now it fades, the clicks get quitter then nothing.
In Brisbane, Aus, I was getting about 15 to 20 clicks per minute.
I put a neon across the tube and I get a faint glow. so maybe the HV is a bit low.
Sign in to Reply
Whereswally
5/1/2011 5:56 AM EDT
I soldered a jumper from the Tube GND to the nearby Neg End of the tube that was previously unconnected and now it is clicking away again
Sign in to Reply
Whereswally
5/1/2011 6:27 AM EDT
If it is still working you can have a look at the live data on Pachube feed, channel 311
http://www.pachube.com/feeds/3037
Sign in to Reply
Whereswally
5/1/2011 6:30 AM EDT
One other thing, where is the best place to place the sensor? In a case outside, plastic case. I gather that gamma radiation will go through a plastic case. I am testing this inside my steel shed presently.
Terry
Sign in to Reply
Whereswally
5/4/2011 7:51 AM EDT
I added a 1000pf (103K) 600v to smooth the HV and now it seems to run 24 hours a day.
But i do note if a 2nd click happens within about 2 seconds it is a bit quieter ... id the cap taking time to recharge perhaps.
Sign in to Reply
gwasik
5/11/2011 8:45 AM EDT
You need to replace R3 with something larger. I used 5.6 M and that should cure the second tick attenuation....
Sign in to Reply
gwasik
5/11/2011 8:43 AM EDT
I finally got around to doing the following mods: A 5600 pf 1KV cap on the output of the diode and replacing R3 with 5.6M . It is no longer sensitive to humidity.
Sign in to Reply
pchow
5/11/2011 11:32 AM EDT
That's good to hear that the two mods worked out for you. I assume that you didn't need to add a (330K ohm) resistor between the base and emitter of the Darlington transistor.
I guess we're still waiting for David's analysis/investigation of Max's kit - looking forward to his findings.
- Peter
Sign in to Reply
Max the Magnificent
5/11/2011 11:40 AM EDT
## ...looking forward to his findings...
Me too! :-)
Sign in to Reply
gwasik
5/18/2011 10:25 AM EDT
If anyone is looking for a readily available test source, pick up some "No Salt" salt substitute from your grocery store. It contains potassium chloride which is a mild beta source.
http://www.youtube.com/watch?v=FEnKTmQ0bdA
Sign in to Reply
Max the Magnificent
5/18/2011 3:47 PM EDT
Really? Wow! I'll let David know (he says he thinks he has it working) plus I will try it out myself (and video it) when the Geiger counter comes back (if I can drab it out of David's fingers :-)
Sign in to Reply
Andresito
5/19/2011 5:24 AM EDT
Hi All,
I have the same problem of many of You:
- I bought the CHANEY kit from Electronic Goldmine
- I assembled it correctly (I think :D)
- and I got the same as others: the LED was on and 200 Hz buzz from the speaker.
What I don't understand in this situation is, that these companies are selling assembled kits. How could they NOT encounter the same problems?
If I send back for repair, could they really repair it?
Cheers,
Andresito
Sign in to Reply
Max the Magnificent
5/19/2011 9:08 AM EDT
I heard from David that he has my kit up and running -- he's documented everything he did with photos -- we will be posting this as a follow-up article sometime in the not-so-distant future -- Max
Sign in to Reply
shiverman
5/19/2011 10:49 AM EDT
Yes well the kit is poorly designed at best.
I sent mine back and they lied saying I used ACID CORE SOLDER when my solder roll says right on it "ROSIN CORE"
They refuse to fix it, refuse to refund anything.
Stay the hell away from them!!
I wish I saw this forum before I bought them, now I'm in big for a fight for my money.
I mean I never heard of ANY electronic device that will DIE because it's HUMID OUT.
That says it all right there.
YOu want it to work, you have to MODIFY it so that it works.
So it's not actually a kit at all since you have to change components to MAKE IT WORK.
One of many things wrong with these.
This is ridiculous that they charge so much for literally the worst kit I've ever come across, KNOW it's bad, but continue to sell it them offer no support or refunds because it's garbage to begin with.
On top of this, they want me to pay shipping BACK to me, and gouge me for another shipping fee!
Nightmare.
Sign in to Reply
Max the Magnificent
5/19/2011 10:54 AM EDT
I must admit that it's a tad frustrating -- I personally like things to work first time -- I'm fortunate enough to have someone like David to turn to (I talk the talk, but he walks the walk :-)
The video of one actually working on YouTube makes me want to get mine back ... I just want to have it sitting on my desk quietly clicking away.
Maybe when you see what David did to mine you could do the same to yours...
Sign in to Reply
pchow
5/19/2011 12:55 PM EDT
Yes, I would have to totally agree, it's really a poor design - but can be salvaged with some simple changes. They should not sell this kit as designed - but I now have a better understand how a Geiger circuit should work after hacking it a bit. Although it's become a quest to get this thing working right. :(
I'm aldo curious what David's changes are, which I asssume will be similar to what I've documented at:
https://picasaweb.google.com/101778441575121007208/Geiger_chaney6981Modified#
The G-M tube is still floating (not referenced to ground, etc.) even in the modified design, but it works.
Anyways, even if you had Electronic Goldmine or Chaney Electronics fix the kit, it would not be as reliable as making the necessary design modifications. - Peter
Sign in to Reply
shiverman
5/19/2011 2:22 PM EDT
They had the NERVE to tell my payment service that ALL their customers are HAPPY with the design.
This blog alone proves they are not truthful.
I didn't want to change the design incase they would repair it, but they are doing nothing to help..so if I don't get refunded I'll have to make those changes ( that's if they even return them to me )
*sigh*
Sign in to Reply
gwasik
5/19/2011 3:35 PM EDT
I have extra components and if anyone would like me to repair or mod theirs, please contact me at my screen name at gmail.com
Sign in to Reply
Andresito
5/24/2011 3:19 AM EDT
AFTER applying Peter's recommendations: MY COUNTER IS WORKING TOO! I'm very happy since I live in Japan. From now on I will check every food&drink before consuming it. (These jerks increased the radiation safety limits here, so literally all contaminated food products are: "Under the safety limit")
Sign in to Reply
Max the Magnificent
5/24/2011 1:03 PM EDT
David has fixed my Geiger counter -- also he's written a GREAT article describing everything he did (http://bit.ly/jclBdM)
Sign in to Reply
Anakron
6/29/2011 9:24 PM EDT
Thank you so much for making this available.
I got a new kit today, revision 04/12/11LW, which did something similar. The schemos include a 100R resistor for the LED but everything else is the same.
The sensitivity was almost nothing, probably a click every 3 minutes or so. I noticed that if I touched the + end of the tube with a single voltmeter probe, it stabilized and I got actual background level, about 25CPM.
To my surprise I had disk shaped 1000pF/500V caps in a drawer (model military suitcase) and fitted one of them standing vertically on the outside of the transformer with one pin to the jumper over to the (middle) case (-) of the GM tube, the other pin along the edge of the board to the cathode of the diode. I also changed R3 to 1MOhm (biggest I had in throughhole).
The board now works beautifully with no double clicks.
Kent
Sign in to Reply
Max the Magnificent
11/3/2011 11:03 AM EDT
Cool Beans!!!
Sign in to Reply
Atomic.dave
12/7/2011 3:31 PM EST
Hello I too have built a chaney kit c6981 with digital display. It seemed to work ok for the most part but it always seemed to have this steady buzz from the piezo. Also noticed that it would go thru batteries quite quickly. I ended up selling it on eBay to a guy in Japan. From there I started off on a journey of building many Geiger kits from a few arduino, a uno based libelium, to a recent cheap 29 dollar one from Electronic goldmine who like Kitusa sells Chaney kits. I bought two as they had a sale for 19 bucks. The first one worked but it had a constant buzz from the piezo. The second one was missing a part which they replaced but I can't get it to work right a the piezo is real quiet. I contacted them but they said that all the geiger (chaney) kits have the same piezo buzz caused by the 9 volt up conversion. They no longer are returning my emails. Anyone care to comment?
Sign in to Reply