At a minumum the ends of the wires must be well tinned, you can also crimp or solder pins on the wires, as long as the pin's size allows insertion. For prototyping it is easier to undo/redo one wire with screw connectors than by using block connectors.
For prototyping, it really doesn't matter -- I don't typically bother with ferrules or such, and I'll happily scrunch multiple wires onto one terminal.
For production, we use crimped ferrules when inserting wires into screw terminals.
However, with spring clamp, you just strip and insert (nothing else required), making sure that ONLY the stripped wire is inserted (since, of course, if your spring clamps on insulation, you get no contact). Also, I wouldn't trust doing multiple wires to a single spring clamp terminal.
IDC is the easiest: insert the wire and close. However, your wire & insulation must be the right size for the terminal, and I'm not sure I'd trust repeated use of most IDC terminals (maybe the swing-style ones are better).
So, do you have any suggestions on where we might obtain these little scamps at a price that doesn't make my lower lip quiver and my eyes water?
The sizing of the connectors is normally such that you can make any size connector by combining 2 and 3 way to get the number of poles that you need (just make sure before you buy.) Priced as singles this will work out as more expensive, but if you make all your connectors out of 2/3 way units, you will go over the 10 or even 25 piece price break. Not a great saving, but a saving nonetheless.
I spend way too much time researching connectors and terminal blocks.
We use PCB & DIN rail terminal blocks extensively, and if you have competent techs, they work very well.
For prototyping, I prefer screw terminals, because you can stuff multiple wires into one connector. However, for production work, I try to specify spring clamp (much faster assembly time, supposedly more reliable) or IDC (which can be great -- IF you can control the terminating wire. IDC's ONLY work for a narrow range of wire & insulation size).
Phoenix Contact's standard stuff can be pricey, so one option is to check out alternate brands (such as OST, TE, and Molex), although my feeling is that Phoenix's quality is better. Maybe the other German brands (e.g. Wago, Weidmuller, and I think some ASI sutff) are less expensive.
Phoenix does have some quite affordable products, too, such as the PST/PT series, the 2.5mm PTSM series, the PTSA, and the PTDA series.
However, when you need a specific size (such as 2.54mm), that can really limit your options. For example, from some quick Mouser searches, that 2.5mm is much more popular than 2.54mm (and cheaper, since you can get a 10-pos PTSA for ~$1).
Finally, use the search, Luke! (Mouser & Digikey both have excellent parametric searching/filtering) I did a quick Digikey search, and found some fixed 2.54mm TB's for <$2.50 (the OST ones).
Maybe the other German brands (e.g. Wago, Weidmuller, and I think some ASI sutff) are less expensive.
Weidmuller doesn't do 0.1" (or even 2.54mm!!) at all, much to my chagrin.
Phoenix does have some quite affordable products, too, such as the PST/PT series, the 2.5mm PTSM series, the PTSA, and the PTDA series
Depending on your hole size and "wiggle" of the connector pin you can get a 3 way 2.5mm into 2.54 spacing with little stress. You could possibly push it to 4. 2 way certainly works fine. If you combine this with my earlier suggestion of breaking it into 2 and 3 way blocks, and if these Phoenix connectors are that much cheaper, then maybe that is the way to go.
Max, come on, ~$1.00 is $0.10 per connection point; even $2.50 for 10 pos is $0.25/point -- a reasonable price if the quality is good.
To get cheaper, I'd say look at going to 2.5mm for the TB (probably cheaper to go with more positions) and look at Phoenix's building oriented stuff (the various PTxx lines) -- in fact, I'd recommend ordering (or begging for samples) a few to see how you like them (for example, the $1.07 PTSA 0,5/10-2,5-F is spring clamp)
It's worth paying a bit more for something if you like it better.
TonyTib - Somehow I missed the OST versions. That is a lot less money. As far as changing pitch to 2.5, for a short connector, that can work. Somewhere in the 5 - 10 pin range it can get difficult to fit, though.
So, do you have any suggestions on where we might obtain these little scamps at a price that doesn't make my lower lip quiver and my eyes water?
Depending on the layout of your board (and this is a long shot), if you have created it as a matrix on a 0.1" spacing with lots of holes for protyping. You could use 2 rows of 0.2" spacing connectors one set back behind the other and offset by 0.1" (with 45 degree input angle). I could help you source those!
@antedeluvian: You could use 2 rows of 0.2" spacing connectors one set back behind the other and offset by 0.1" (with 45 degree input angle). I could help you source those!
But then we'd have to re-spin the board -- I can make do with just one of these shelds for my current project (although I would build a bunch if we can get these connectors cheaply enough) ... but thinks for the offer.
The way we used to build a prototype was much cheaper. None of this "looked at prices online" junk.
Figure out who is the local sales rep in your area. There will be one, you may have to dig. I kept a file of line cards, which sounds very quaint today.
Call them on the phone, yes the phone. Talk to one of the humans.
Tell them you need samples. The project is under NDA, but if the "can't really say, Q clearences and all, you understand" contract comes through it will be about a million pieces a year, month, whatever. Get the sales person excited. You want to hear them drooling on their phone.
Get the samples, and your golden. If you are good, you can also get a free lunch. Too bad the contract fell through. Sigh.
I build the first 10 production units at a startup this way. We did buy a lot of parts, once things took off. I also build a number of prototypes for another company that never became real products. This is how the game is played, so hate the game, not the player.
The Phoenix Contact part may be expensive, though I've always been impressed with their technical literature and the research behind their product. So Max buys the Phoenix Contact part and consequently has to dine on Top Ramen for a month. This would be a bad thing for Max, but it might be a good thing for us readers as it could generate interesting columns such as, "Does Dining On Top Ramen for a Month Make One a Better Engineer?" :)
For work, I pretty much specify Phoenix because the quality is good, availability is good, they have a very wide range, they have 3D models, and the price is OK (especially since we get a good discount from our local distributor) -- and I try to choose the more affordable ones.
For my own use, however, I'm more price sensitive, so I have a mix of Phoenix, OST, Wago (from eBay), and some unknowns (from our local surplus shop, Excess Solutions, which sometimes has Phoenix at great prices). The OST seem well made, too, but the plastic does have a different feel (maybe not worse, just different, although some of my "unknowns" don't feel as well made).
I can't comment about Aliexpress or Hong Kong vendors, other to say that Aliexpress doesn't seem to have good customer service (surprise, surprise!), and that I have some some (non-Electronic) made in China items made of cheap, stinky plastic -- and the stinky smell doesn't seem to go away, ever.
To be fair, I've had good luck dealing with Stationary Art in Hong Kong (I got my superb Kuru Toga Roulette pencil from them at a great price), Seeedstudio (Arduino stuff), and Gold Phoenix (PCBs - good if you're experienced but they don't hold your hand).
@TonyTib: To be fair, I've had good luck dealing with Stationary Art in Hong Kong (I got my superb Kuru Toga Roulette pencil from them at a great price), Seeedstudio (Arduino stuff), and Gold Phoenix (PCBs - good if you're experienced but they don't hold your hand).
I like the stuff I've used from Seeedstudio, but they could really do with someone in support who can read and write good English LOL
Hi Max, Have you seen this Kickstarter project for custommisable boxes for Arduino and other form factors? click here. Only a few hours to go before the funding stops, but the stretched goal already reached.
I have got my Microduino Kickstarter boards through the post yesterday, all I need now is to get the builders out of my workshop, so that I can write a blog about using these minature bits of kit
Wet weather still causing problems in the UK and it seems like Crusty Mansion is at present an epicentre.
@Crusty: I have got my Microduino Kickstarter boards through the post yesterday, all I need now is to get the builders out of my workshop, so that I can write a blog about using these minature bits of kit.
Max, you must be right about them not sending these 0.1" pitch blocks to Australia, I could not find any from any of my suppliers. Smallest I could find was 3.5 mm. However I did find these at 5mm pitch which are nice - just push the wire in and press the clip down (like speaker terminals). I've seen similar ones before but not so neat. They work out about 50c per way. if you could find these in 0.1" pitch they'd be good - and they make DIP switches that size, so why not terminals?
I'd go along with the suggestions of getting 2-and 3-way and combining them, they are usually cheaper (per way) than the bigger ones. I had to change one the other day, one of a bank of 4-3-way ones. They have protrusions and grooves that lock them together, and of course by sod's law I had to take them all off to get at the one I had to change. Why is everything always so difficult?
That would be cool if they made them in 0.1" pitch
Aah, but they do. Anything that says "tension clamp", "spring loaded" , "spring clamp" works pretty much on this principle. Provided you are using a solid core wire, there are some you just push into the connector hole. Removing means pressing a lever or inserting a (tiny) screwdriver.
I think you were right to go with screw terminals -- they're handy for prototyping because you can pretty much stuff anything in there (of various sizes and amounts) and get them to work, at least for a while (I always tug on both wires if I'm connecting two wires to a screw terminal).
Pretty much all spring clamps will work with stranded wire, but you have to open & close the spring, with a screw driver (which needs to be appropriately sized - and sometimes it's tough to hold the board, use the screw driver, and insert the wire), with levers (which can take a bit of force to operate), or possibly something else, depending on the particular model.
@David: They have protrusions and grooves that lock them together, and of course by sod's law I had to take them all off to get at the one I had to change. Why is everything always so difficult?
Don't talk to me about life being difficult... I'm married! :-)
Do you remember that 4x4x4 3D LED cube I built? The hardest part was the transparent plastic "cage" -- it was like a 3D jigsaw without instructions. I kept on getting it almost together before finding the final piece wouldn't fit. When I did finally get it together and tried to put it on the cube, I discovered I'd effectively got it "inside out" so hat thehole for the power cord was on the wrong side... it took hours!!!
As an aside, one thing the spring-clamp type of terminals - especially those not requiring a TFS to operate - are very good for is to put next to a breadboard for connecting power or signals. They make connecting them a pleasure, and you are not tied to having a fixed arrangement. You can use speaker terminals for this as well, but they are usually a lot bigger - which can sometimes be an advantage if you have five thumbs on each hand like me.
@David: ...are very good for is to put next to a breadboard for connecting power...
I've started using a 10A switched mode 5V power supply that's really well regulated -- I have four power leads coming of fit each with a 2.1mm male plug on the end -- I can plug these directly into an Arduino -- or in th ecase om my breadboards ech I connect the breadboard to one of those 2.1mm female connectors with two screw-terminals -- so then I can just plug one of my flying power cables into this -- it make slife really simple :-)
@Max...I have thought of doing that myself, and in fact used something similar when I was playing with my big VF display, which takes 1.4A max. But for development work I prefer having a supply limited to about 1/2 Amp - even less sometimes - that way if I do something silly (which happens not infrequently) then the chances of permanent damage or letting the smoke out of something are a little reduced. The 78M05 limits at 0.5A or you can even use a 78L05 which limits at 100mA. I am working (mostly in my mind at the moment I will admit) on a breadborad develoment system - pluggable breadboards and +/-12V and +/-5V power rails, but might think about having various current limited supplies available (maybe even a variable limit on the +5V using the good old 723 regulator). That way, with my clumsy fingers and addled brain, I will have less chance of frying expensive chips... :-)
"The electrical simplicity of the connector belies the complex mechanical design needed. The contact itself is a tradeoff between mechanical strength, conductivity, clearances, corrosion resistance, gas tight, surface area, regulatory requirements, pressure and vibration resistance. The last item is often covered by a patent. Take a look at the 13th page of this document in the section marked "The principle of vibration resistance".."
...that's the category under which Digikey lists these items, although actually you're mixing the Phoenix Contact (6 amp) series in with the TE/Buchanan (10 amp) part numbers. I like these blocks for PCBs but it's so darn difficult and expensive to get a circuit board trace that you can trust to handle 10 amps (2 oz copper and all that)! So occasionally on my own designs I'll use them on a PCB but it's just where I'm hand-wiring that portion of the circuit on the board. (You'll also note the pins are slightly larger diameter than the holes they provide on the pre-punched board.) Where I only need up to say an amp per circuit the regular dual-row IDC variety seems to do nicely, if you don't need all that density just wire up one row per connector and you get the same circuit density much cheaper. (You could go to 2mm series too but it only improves density about 25% and you may pay a premium for it.)
So with the screw terminals you're really paying for current AND circuit density, wouldn't pay for both if you don't need it. In a lot of cases you might just relocate the "connectivity issue" to the other end of the ribbon cable, and just pocket the savings from that solution.
As several other people mentioned, if you are looking for a cheap solution then you can use the Chinese stuff for non-mission critical projects. Search for screw terminal blocks on Deal Extreme (www.dx.com) and you will find a whole range of options that are much cheaper than DigiKey and probably good enough for most hobby applications. Shipping from DX is free to the US and several other countries. Sometimes it can take two or more weeks so don't expect overnight delivery like you can get from one of the reputable US distis. If you know anyone that is visiting Shenzhen then ask them to go to the electronics market in Hua qiang bei lu. They will be able to find any kind of connector that you can dream of, and many that you have never even dreamt of :) . Even without bargaining, USD$10 will get you enough terminal blocks to last you quite a long time. The team at SEEED Studio (www.seeedstudio.com) put together a map of where you can find things in Hua qiang bei lu. There is a downloadable version here: http://www.seeedstudio.com/depot/shenzhen-map-for-makers-p-1585.html?cPath=70_72
"Slightly" off topic but one day in the Hua qiang bei lu market is not enough. I think that a visit to the market should be a required part of the education for many engineers. I made sure some of the engineers in my team spent several days there in order to understand how the black cell phone market designs phones. It was enlightening and it was worth the investment. When you go there plan on at least a week. I don't understand why some geek travel company doesn't organize week long tours that cover China's different technical markets. The savings you can get buying all the stuff there can pay for part of the trip. A few days in Sheznen at the electronics market. A day in Shanghai to visit the smaller electronics market there but there is a whole section that deals in chemical lab equipment, which you cannot find in the Shenzhen market. I'm sure there is an area in China where they have a market that speciallizes just in heavy machinery like mini-lathes/mills and their full size cousins.
1. Don't buy/stuff connectors that you're unsure that you're going to use. If vanity requires that the board look pretty (fully-stuffed) from day one, you get to pay for it. Otherwise, as usual, designing/building for the worst case will simply cost you.
2. Design the board for the least per-port cost of the connectors. This might mean laying it out to accept only 4-port connectors at ~$0.35/port rather than for some of the outliers at ~$0.60/port. Because the blocks often don't snug-up to each other while maintaining their 2.54mm centers on the grid from block to block, you have to do this up front (unless you want to *try* to shave the blocks down). You may also benefit by standardizing on smaller connectors by moving up the quantity discount scale. See again #1.
3. Buying no-name parts retail from China can be a fine option for one-offs, but you can't always count on getting the same parts during subsequent buys. The usual time/cost trade-off always exists here for shipping.
4. Basically, plan ahead. One nugget of common wisdom is that you don't design a project without choosing an enclosure ahead of time. Although with 3D printers (or milling equipment), you can thoeretically make an enclosure after the fact (likely at a higher cost). In general, the design isn't done until you've gone through and settled on your entire BOM and checked the parts for availability -- otherwise you "get" to buy your way out of the hole you've dug.
@Ewertz: Don't buy/stuff connectors that you're unsure that you're going to use...
You make some very good points -- we will take these into consideration for the future if we go to a larger build -- but for the first 1-off I do want it to be fully populated so (a) I can see it in all its glory and (b) it's ready and waiting as I stuff more and more things into my Prognostication Engine
@Sir Cut: When i'm in a pinch I've ordered the two port terminal blocks at $.10 a peice
This would be a great solution except that the pitch is 5mm -- we need a pitcgh of 0.1" = 2.54mm -- but I will look around the Tayda site to see what else rthey have to offer -- thanks for the suggestion
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used on the Mars on EE Times Radio. Live radio show and live chat. Get your questions ready.