EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: android on November 25, 2016, 12:11:44 pm
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I've just designed a small USB device (using a PIC16F1455) about the size of a thumb drive that has a type A USB plug. When connected, it presents as a USB keyboard (yep, boring :D). It works fine and i'm quite happy with it but I wanted to be able to easily reprogram it. To accommodate that I brought the VDD, VSS, VPP, PGC and PGD signals out as 0.1 inch spaced fingers on the "non plug" end of the PCB and decided to figure out how to connect it later.
Well, "later" has come...and I still haven't figured out a simple way of building a suitable socket for this "edge" connector :(.
Any ideas?
Edit: added word "socket" to subject
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I don't have an answer to your question, but if you're ordering custom PCBs, I recommend investing in a tag-connect cable. http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=TC2030-MCP (http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=TC2030-MCP)
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Why not use regular headers? (angled or upright)
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Are you talking about a regular edge connector, like this?
http://www.digikey.co.uk/product-detail/en/sullins-connector-solutions/EBC05DRTH/S3291-ND/927243 (http://www.digikey.co.uk/product-detail/en/sullins-connector-solutions/EBC05DRTH/S3291-ND/927243)
(http://media.digikey.com/Photos/Sullins%20Photos/EBC05DRTH.JPG)
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@jdraughn Thanks for that ... I've already had the PCBs made, but I'll consider a tag-connect for a future project
@jeroen79 I didn't want pointy things sticking out of it because it may often be carried in a shirt pocket
@nali Yes that's perfect :) and only AU$5 ...But costs $34 shipping unless I order $200 of stuff.
I might try jury-rigging something using a clothes peg and some veroboard instead ;D
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Old motherboard with ISA slots and a saw?
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I had a similar problem for my pointless christmas project where I needed to program ~8 boards but didn't want to waste a permanent connector. I looked at the tag connect, saw the price, went meh. So I did this instead.
(https://www.eevblog.com/forum/projects/any-ideas-for-a-diy-5-pin-edge-connector/?action=dlattach;attach=273541;image)
You have to apply pressure while programming to get a good enough connection, but it works well enough for a temporary programming jig.
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http://au.element14.com/3m/3358-0001/card-edge-connector-socket-10/dp/1369088 (http://au.element14.com/3m/3358-0001/card-edge-connector-socket-10/dp/1369088)
http://au.rs-online.com/web/c/connectors/usb-d-sub-computing-connectors/edge-connectors/?searchTerm=edge+connector#esid=4294958385&applied-dimensions=4294882088&sort-by=Number%20of%20Contacts&sort-order=asc (http://au.rs-online.com/web/c/connectors/usb-d-sub-computing-connectors/edge-connectors/?searchTerm=edge+connector#esid=4294958385&applied-dimensions=4294882088&sort-by=Number%20of%20Contacts&sort-order=asc)
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Butcher a dollar store full size SD card reader for the contacts. The pitch for pins 1-7 is compatible
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@jeroen79 I didn't want pointy things sticking out of it because it may often be carried in a shirt pocket
Use pin headers but keep a dummy plug on them when the wired plug is not in use?
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Well, this is what I've come up with...I don't know whether it works yet because the PCBs haven't arrived, but it looks promising.
Total cost: bugger all ;D
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That wont work reliably because of fractional differences in the length of the pins and the lack of any resilience to equalise their contact pressures.
For the contacts, try forming them out of hard-drawn (stretched) tinned copper wire (unless you've got gold or silver plated phosphor bronze spring wire in stock), mounted in a piece of 0.1" pitch perfboard. To provide the required resilience, stretch an O ring over the strip of perfboard and form each contact over the O ring. If you use veroboard instead of perfboard, youll need about an inch between where the contact is soldered and the O ring to allow the wire to flex. I'd lock it through adjacent holes in the board, take it 1" along the track trackside, through a hole, up and over the O ring and back through the next hole finishing with a rightangle bend as a stop to retain it It would only be soldered at the end furthest away from the O ring. It will need quite a bit of clamping pressure so maybe use a toggle clamp?
Alternatively, butcher a SD card socket for some nice sprung gold plated contacts with the correct pitch, that could be easily fitted to a clothes peg like your current idea. I'd put a rubber pad on the other jaw so it cant slip easily, and solder the programming cable to the contacts, with a SIL header on the other end to suit your programmer.
Next time, *DON'T* use an edge connector if you aren't willing to pay for the mating socket. A better choice is to use unpopulated plated through holes using Sparkfun's offset header footprint (https://www.sparkfun.com/tutorials/114):
(https://www.sparkfun.com/tutorial/SneakyPete/mod1.005.jpg)
which in conjunction with a long pin header forms a sprung contact plug/socket.
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You can buy small enough pogo pins that will insert right into a female .1" header like you have there which will allow the spring pressure to make good contact with all the pads. I use this for some small boards I have that I just need to one time program and go.
Took a picture of my adapter that I just plug into the pickit cable. Just a male .1" header soldered to a female .1" header and the back ends of the pogo pins shoved into the female header. I don't have a clip or anything, but I'm not holding it onto the target for more than a few seconds for programming anyway.
(http://higginstribe.com/uc/pic/pogo-pins.jpg)
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yes you can make some sort of tag connect using pogo pins they are realy cheap (opposite to the tag connect althought it's a brilliant idea)
I bought a 100 pogo pins pack for some dollars, and now I make my own connectors with it.
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using a PIC16F1455
That appears to be SOIC-14. Why not use a SOIC programming clip? Clips right on the chip. 16 is common, it should work.
http://www.ebay.com/itm/SOIC16-SOP16-Flash-Chip-IC-Test-Clips-Socket-Adpter-Programmer-/182057633669 (http://www.ebay.com/itm/SOIC16-SOP16-Flash-Chip-IC-Test-Clips-Socket-Adpter-Programmer-/182057633669)
or build it yourself,
http://www.ebay.com/itm/Programmer-Test-Clip-SOIC16-SOP16-DIP16-Pin-Adapter-Board-IC-Lead-Pitch-1-27mm/371758787016 (http://www.ebay.com/itm/Programmer-Test-Clip-SOIC16-SOP16-DIP16-Pin-Adapter-Board-IC-Lead-Pitch-1-27mm/371758787016)
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That wont work reliably because of fractional differences in the length of the pins and the lack of any resilience to equalise their contact pressures.
...you were absolutely right of course Ian. It was a complete failure when I tested it :(
Your SD card idea reminded me that I already had some SD card adapters from eBay so I decided to see if I could use them. Inside each was a card eject spring which fitted perfectly over a header pin, so I snipped one into 5 lengths and soldered them to the header pins. (See pics). I'm not suggesting that this is ideal, but the jig seems quite reliable...after a little jig-gling :-DD
As suggested by TheDirty, I've ordered some pogo pins from eBay (keywords "P75-LM2 1.02mm Length 16.5mm 100g Spring Test Probe Pogo Pin 6 Blade Tip") and will see if that is any better.
Also, I found another interesting alternative 5-way spring-loaded connectors by Preci-Dip (http://au.rs-online.com/web/p/pcb-pin-socket-strips/7020183/) (see pic) but I'll leave that for a rainy day.
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I do it using a very similar method to what Ian M does, inspired by the sparkfun staggered pin style.
My holes are straight (not staggered) , and I stagger the pins on the connector I push in.
You need to use 32mil holes (0.8mm) , most header pins are 0.8diagonal or a bit less so a nice snug fit.
My ATMEGA projects all use the ATMEL 6pin connector layout, you just plug a some of the really long pin headers (20mm each side) into a ribbon connector then artfully bend them, I file the ends a little bit, its easier to get started.
I also use a 4pin TTL serial connector too with staggered pins. The ground pin is longest, its second from the end (standard sparkfun arrangement)
With both it helps to solder to a bit of veroboard to stabilise it and give you something to hang on to.
I've programmed/calibrated more than 2000 PCB's with these two.
See attached photo.
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These nice people make "clothes-peg" style pogo-pin debug adapters in many options of pad pitch and count: https://item.taobao.com/item.htm?id=42343856957
Now even with choice of different styles of pogo-pins depending on whether you use pads with hole or without (as far as I know, LM type is good for pads with hole, H type for pads without hole).
I've used their older version for a few years now and they've become indispensable.
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Nice find Jane,
They also have these style for when you need to get your test pins nearer the middle of the PCB
https://world.taobao.com/item/43640414794.htm?spm=a312a.7728556.2015080705.15.kXQBFY&id=43640414794&scm=1007.12006.46753.i42343856957&pvid=1cd64aee-c7de-44ce-9229-ae4860b0391a
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No connector can be the solution
Just make 5 circles pads on the pcb, and make a connection cable based on pogo pins
(https://ae01.alicdn.com/kf/HTB1w.cwKFXXXXaBaXXXq6xXFXXXc/224668853/HTB1w.cwKFXXXXaBaXXXq6xXFXXXc.jpg)
https://pt.aliexpress.com/item/Best-Promotion-100-Pieces-P75-B1-Dia-1-02mm-100g-Spring-Test-Probe-Pogo-Pin-Phosphorus/32554214182.html?spm=2114.02010208.3.11.kgKsYz&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10068_10084_10083_10080_10082_10081_10060_10061_10062_10056_10055_10037_10054_10059_10032_10099_10078_10079_10077_426_10073_10102_10096_10052_10050_425_10051,searchweb201603_2&btsid=5b5309a2-e1f0-4f7d-8f45-aa5af37ecd2a
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I don't have an answer to your question, but if you're ordering custom PCBs, I recommend investing in a tag-connect cable. http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=TC2030-MCP (http://www.microchip.com/Developmenttools/ProductDetails.aspx?PartNO=TC2030-MCP)
What's the advantage of Tag-Connect over a plain old 2x3 pin header (2.54mm pitch)?
I downloaded the Tag-Connect footprint; the "legs" version (right) is bigger than the header ("J1"), and the "no-legs" version (left) is barely smaller.
See attached image.
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I can't see the advantage either,
It gets pretty busy around the prog connector (see image) on my PCB's
Those 4 big holes eat up a lot of real estate where tracks could be running.
The normal 6pin ribbon connector receptacle is pretty huge though, but that's only a problem if you have through hole components near the prog connector.
Sure their connector is smaller than the ribbon connector, but it's space on the PCB that matters.
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I can't see the advantage either,
It gets pretty busy around the prog connector (see image) on my PCB's
Those 4 big holes eat up a lot of real estate where tracks could be running.
Thinking about it some more, the "no legs" version has a small advantage - not only is it a little smaller than the header, but there are only 3 thru holes instead of 6, leaving more space for traces on layers other than the top.
On the other hand, it looks harder to keep the no-legs connector attached (you need the dongle thingy on the bottom of the board).
Seems like a very minor advantage. But I'm interested in contrary opinions.
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Tag Connect advantage in the small form factor is that is has guide pins. And that the cable is already made and stocked at a dealer near you. The guide pins basically aid when hand-flashing a large pile of boards... (IMO this is a fairly minor advantage, just because flashing large piles of boards by hand is not that great a system, to begin with.)
I would assume the larger footprint/cable might be good for dev use. And for longer flash time and/or JTAG diagnostics/testing. So you get connector without having to buy and install/assemble a physical connector... of course, there is the pcb area cost you mentioned. For dev use, though, it might be nice. Once firmware is debugged and stable, you can change to smaller footprint. Or use that small footprint and base thing you mentioned for dev use.
I have used Tag Connect. It's fine, if you want a compact, ready-made solution. The ergos of the cable/interface are somewhat lacking, though.
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Tag Connect advantage in the small form factor is that is has guide pins. And that the cable is already made and stocked at a dealer near you. The guide pins basically aid when hand-flashing a large pile of boards...
I see that, if you're going to flash production boards by hand.
I would assume the larger footprint/cable might be good for dev use.
That I don't see. Long ago I made a couple ICSP cables that terminate in a 2x3 female header (with one pin knocked out for polarization); all my dev boards have 2x3 headers for ICSP.
The only advantage I can see from using the larger legged Tag-Connect is that you don't have to make that cable. But anybody making dev boards surely knows how to solder, or has somebody to do it for them.
Surely if there were a demand for ICSP cables ending in 2x3 female headers, you'd see them on eBay for $4.
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The larger footprint locks on, though. For dev, you might find it expedient to leave the cable plugged in. Of course, this is nothing that "wiggly holes" don't also solve.... So ??
I agree, little need, but same thing can be said for Arduino shield. Anyone can make their own prototying equipment. And many do. Only reason I have any exposure to Tag Connect is working with third party hardware. I eventually removed the pin assembly from the cable to affix it to something that can attach to an arbor press or a CNC.
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The larger footprint locks on, though. For dev, you might find it expedient to leave the cable plugged in.
Header pins lock on just fine.
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Yeah, I know. You're preaching to the choir. But some people rather buy than to make. Easier to order new one than to manage your own tool chain. I guess it depends on your profit margins, lol. If you make $200 a board, you can splurge a little on your ICSP/JTAG interface.
I would personally be more interested if someone sold little standard pogo pin arrays, 1x5, 2x3, 1x6, 2x5, etc, as SMD pcb components.
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Tiny PCB's with hole patterns for pogo pins would be good idea, one could make them with all that spare pcb area on a panel, or utilise the rails.
I make simple bed of nails testers using an unloaded PCB, but it's really hard to align the pins and keep them aligned. Around the edges it's easy enough to get the pins straight by sandwiching another PCB on top, but you can't get the soldering iron in to get to pins more than about an inch in. I've made a jig from a piece of wood with a groove and a soft spring as a third hand to hold pins vertical while soldering.
The prog connector and serial diag ports tend to be near the centre of the PCB, and with ten pogo pins pushing up, the PCB bows up in the middle, and breaks contact sometimes, that's why I prefer to use a plug in 2x3 arrangement (& 1x4). It can also be used to test/upgrade the PCB's when they are assembled inside equipment.
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I make simple bed of nails testers using an unloaded PCB, but it's really hard to align the pins and keep them aligned. Around the edges it's easy enough to get the pins straight by sandwiching another PCB on top, but you can't get the soldering iron in to get to pins more than about an inch in. I've made a jig from a piece of wood with a groove and a soft spring as a third hand to hold pins vertical while soldering.
When I did this last I used two PCBs spaced one above the other.
The top on had clearance holes drilled for the pogo pin body.
The rear of the pogo pins were soldered to the pads on the bottom board.
I used cut down machine screws to space the boards apart and to act as guides for the DUT as it was placed on the jig.
The screws went in the PCB mounting holes.
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I make simple bed of nails testers using an unloaded PCB, but it's really hard to align the pins and keep them aligned. Around the edges it's easy enough to get the pins straight by sandwiching another PCB on top, but you can't get the soldering iron in to get to pins more than about an inch in. I've made a jig from a piece of wood with a groove and a soft spring as a third hand to hold pins vertical while soldering.
When I did this last I used two PCBs spaced one above the other.
The top on had clearance holes drilled for the pogo pin body.
The rear of the pogo pins were soldered to the pads on the bottom board.
I used cut down machine screws to space the boards apart and to act as guides for the DUT as it was placed on the jig.
The screws went in the PCB mounting holes.
It's not really necessary to re-invent the wheel for PCB test fixtures. It's very cheap to buy the standard test fixtures which are customised by milling holes for the pogo pins and a cavity for holding the PCB: https://item.taobao.com/item.htm?spm=2013.1.0.0.S5RVZ6&id=45231559017
If you don't have the milling machine you can ask the shop to make them for you for a nominal fee. Once you've got the test fixture base, you can also just get the pogo pin / PCB holding plates cut for the next one.
Though if you can arrange for your PCB to have the test / programming pads located together in one location, you can just use the clothes-peg style mentioned earlier (but if you're asking someone else to do the testing, of course it's convenient to have a complete test fixture where someone just presses a button and a red or green light illuminates).
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When I did this last I used two PCBs spaced one above the other.
The top on had clearance holes drilled for the pogo pin body.
The rear of the pogo pins were soldered to the pads on the bottom board.I guess you are using the pogo pin holders? and soldering those in.
"Clearance holes" won't fit over the head of a pogo pin.
I just solder the bare pogo pin by itself for small connectors (i.e. with a 32mil hole on the PCB), for the bigger connectors (with bigger holes) I put them in the holders.
I use 16mm male-female headers and the male bit sticking up aligns the PCB.
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Another idea is follow Atmel ICE idea and use 1.27mm headers
http://www.mouser.com/ProductDetail/Amphenol-FCI/20021121-00006C4LF/?qs=sGAEpiMZZMs%252bGHln7q6pmzWpWpY27fVZrlgFe%252bGyRzo%3d (http://www.mouser.com/ProductDetail/Amphenol-FCI/20021121-00006C4LF/?qs=sGAEpiMZZMs%252bGHln7q6pmzWpWpY27fVZrlgFe%252bGyRzo%3d)
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Another idea is follow Atmel ICE idea and use 1.27mm headers
http://www.mouser.com/ProductDetail/Amphenol-FCI/20021121-00006C4LF/?qs=sGAEpiMZZMs%252bGHln7q6pmzWpWpY27fVZrlgFe%252bGyRzo%3d (http://www.mouser.com/ProductDetail/Amphenol-FCI/20021121-00006C4LF/?qs=sGAEpiMZZMs%252bGHln7q6pmzWpWpY27fVZrlgFe%252bGyRzo%3d)
I like that idea, but how does one setup the female connector? 1.27mm pitch seems too small to easily install crimped pins into a female housing...
I just ordered a "legs" Tag-Connect cable. I have the idea that if I put the "no-legs" footprint right on the edge of the PCB, I could fasten the cable (with a bit of modification) to the edge of the PCB, without those huge thru-holes normally required.
If I can make that work, I'll have a slightly smaller footprint, no 6-pin header to install on dev boards, but still a stable debug connection.
It seems worth a try, anyway.
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Thank you all for your many tips.
I went with the pogo pin idea and built my (mark 3) clothes peg jig using a sacrificed PCB held together with hot snot. It works really well. :D