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A Sensor for All Seasons

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Duane Benson
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Fun with sensors
Duane Benson   10/31/2013 6:13:36 PM
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One of the extras I put into the little PIC sensor board is a set of three pins connected to the ADC of the PIC. That way, you can use the same board with the same command set equipped with an ultrasonic sensor or an analog distance measuring sensor.

David Ashton
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cool stuff
David Ashton   10/31/2013 6:48:44 PM
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Very cool stuff Max (and Duane) but one question - what is the LDR for in between the two ultrasonic transducers on the SFR08 module?

Max The Magnificent
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Re: cool stuff
Max The Magnificent   11/1/2013 12:41:00 PM
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@David: I'll let Duane answer this because he has some of those modules -- I'm just going to use the cheap ones :-)

Crusty1
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Re: cost cutting cool stuff
Crusty1   11/2/2013 4:36:27 AM
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@Max,Duane,David:

Does Max need multiple ultrasonic sensors?

Why not take a leaf out of the radar technology and have a spinning ultrasonic dector turret on the robot. This could be turned by a stepper motor, so you would know where it was pointing relevant to the robots fixed chassis.

It might also look very cool like Robby from the Forbidden Planet ?

 

David Ashton
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Re: cost cutting cool stuff
David Ashton   11/2/2013 6:25:55 AM
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True, Crusty, it would look VERY cool.  And Max has a spare motor driver on his arduino shield, so he could use that to rotate the US rangefinder.  

Max The Magnificent
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Re: cost cutting cool stuff
Max The Magnificent   11/2/2013 11:13:38 AM
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@david: And Max has a spare motor driver on his arduino shield, so he could use that to rotate the US rangefinder. 

Also those Adafruit motor driver shields are cintrolled using I2C and are stackable, so I can add more motors if I need to do so.

Max The Magnificent
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Re: cost cutting cool stuff
Max The Magnificent   11/2/2013 11:11:44 AM
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@Crusty: Why not take a leaf out of the radar technology and have a spinning ultrasonic dector turret on the robot. This could be turned by a stepper motor, so you would know where it was pointing relevant to the robots fixed chassis...

That's certainly a possibility -- but in the fullness of time I hope to have my Pixy machine vision sensor mounted on top of the robot ... I'll think about it...

Duane Benson
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Re: cool stuff
Duane Benson   11/1/2013 12:58:10 PM
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David - I don't know why it's there, but one of the I2C commands will return the light level from the LDR.

jjulian274
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Re: cool stuff
jjulian274   11/1/2013 4:41:08 PM
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I'm not sure either, but my guess would be that the LDR is there for a light following robot.  You can follow a light and tell if there are any obsticals in the way.


At least that is why I would put it there.  That's my story and I'm sticking to it.


You could also use it for chasing after a lighted object (say a ball), and use the rangers to guide you in to pick it up.

Max The Magnificent
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Re: cool stuff
Max The Magnificent   11/2/2013 11:09:07 AM
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@jjulian274: You could also use it for chasing after a lighted object (say a ball), and use the rangers to guide you in to pick it up.

That's what I want to use my Pixy Machine Vision sensor for.

David Ashton
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Re: cool stuff
David Ashton   11/2/2013 6:41:02 PM
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@Max: Jjulian said: "You could also use it for chasing after a lighted object (say a ball)".

Or your cat??

Paul A. Clayton
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Even neutrinos?
Paul A. Clayton   11/1/2013 7:10:24 PM
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"You name it, and my robot will sense it."

What kind of shielding are you planning to use to minimize false positives in your neutrino sensor? ☺

Are you also planning to detect ionizing radiation? Gas leaks? Carbon monoxide? Pollen/particulate count? (With temperature, humidity, and barometric pressure, the robot might be half way to being a mobile weather station--lacking wind speed and direction and precipitation measurement [perhaps also illumination determination--cloudy, partly cloudy, sunny].)

David Ashton
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Re: Even neutrinos?
David Ashton   11/1/2013 7:49:11 PM
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@Paul....and Duane / Jjulian above... "[perhaps also illumination determination--cloudy, partly cloudy, sunny].)"

THAT'S what you can use the LDR for!@

Max The Magnificent
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Re: cool stuff
Max The Magnificent   11/4/2013 5:50:25 AM
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@xufeifei: The sound PCB is great, but see my green bee

Wow -- that is fantastic -- how long did it take you to make that?

David Ashton
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Re: cool stuff
David Ashton   11/4/2013 6:25:54 AM
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Max - it does look cool - but this xufeifei is posting stuff all over EET and trying to sell stuff (there is a link on the bee pic.)  How's yer old mum then?

Max The Magnificent
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Re: cool stuff
Max The Magnificent   11/4/2013 6:39:31 AM
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@David: ....but this xufeifei is posting stuff all over EET...

Bummer -- I'll see what I can do about that.

Mom is great -- I'm at my brother's house -- she will be round here in about 30 minutes -- we'll take a stroll to the shops at the bvottom of the road -- tomorrow I'm going wo her writing club with her -- it's great being over here and not working 12 hours a day :-)

Devad
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A sensor I can't find .....
Devad   11/8/2013 1:45:18 PM
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I need to measure pressure. Two application.

1. Water pressure. Actually differential h2o pressure with absolute  pressure of 40 to 60 psi would be great.  

2. Air pressure.  Absolute air pressure between 30 - 50 psi.

Having a tough time finding either of these sensor that are afforable.  Say around  5 bucks ... less would be better.  I've found some in the 35 to 100's of dollars.  I'd like to have digital output for input to an Arduino.

There much be a cheap way to measure pressure.  Medical devices are very low pressures but I would think the auto industry would have devices in the ranges above. I just can't find them.

 

 

 

Les Hammer
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Re: A sensor I can't find .....
Les Hammer   11/8/2013 5:30:57 PM
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RE: Ultra sonic sensor calibration - the speed of sound is proportional to the square root of the temperature in Kelvin.  You will need to take that into account.

RE: Measuring pressure cheaply - weld a disk on the end of a pipe.  Seal the pipe if you want the air that is in it to be your reference.  Glue a strain gage to the disk.  The strain will change with the chaging air pressure.

Max The Magnificent
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Re: A sensor I can't find .....
Max The Magnificent   3/19/2014 3:10:48 PM
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@Les Hammer: Measuring pressure cheaply - weld a disk on the end of a pipe.  Seal the pipe if you want the air that is in it to be your reference.  Glue a strain gage to the disk.  The strain will change with the chaging air pressure.

Clever! I'd be interested in seeing a blog on this with a reference design showing the accuracy and resiolution that could be achieved with such a design. Are you interested in writing such a column?

Les Hammer
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Re: A sensor I can't find .....
Les Hammer   3/19/2014 4:48:38 PM
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Actually the disc on the end of a pipe pressure measurement is an experiment that we do at the Colorado School of Mines.  We have 12 units built up and connected up in parallel to a commercial Omega unit.  We run a LabVIEW program to take data from both - using the Omega as a reference, then we analyze in Excel.  The worst unit that we have gets about 11% linearity error.  I haven't correlated linearity to how much glue was slopped on the strain gage.  I could send you more details later.

~~Les Hammer

Max The Magnificent
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Re: A sensor I can't find .....
Max The Magnificent   3/19/2014 4:52:19 PM
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@Les Hammer: The worst unit that we have gets about 11% linearity error.  I haven't correlated linearity to how much glue was slopped on the strain gage.  I could send you more details later.

Please do. I'm interested in hearing about things like the length and diameter (and thickness and material) of the pipe -- also the end cap -- the type and cost of the strain gauge -- what effect (if any) does pre-presurizing the pipe have.... inquiring minds want to know these things...

Les Hammer
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Re: A sensor I can't find .....
Les Hammer   4/1/2014 9:46:47 PM
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@Max The Magnificent - how do I submit the blog on the inexpensive pressure gage?  It includes a NI LabVIEW VI and an Excel program.  Do your readers care if the spelling is gage or gauge, or is that a topic for another discussion?  :-)

~~Les

Max The Magnificent
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Re: A sensor I can't find .....
Max The Magnificent   4/1/2014 9:50:17 PM
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@Les: ...how do I submit the blog on the inexpensive pressure gage?...

Hi Les -- I'm at the EE Live! conference this week -- one of the NI guys won today's Gadget Smackdown.

I'm up to my armpits in alligators this week -- email me next week at max.maxfield@ubm.com and we'll talk about the best way for you to get me your blog. Cheers -- Max

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