Wiring to board

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npdjapan

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Hi all
Thanks for constant help and information!
Another newby question here.

I have a teensy3.5 with pins.
My prototype on breadboard is working fine!

In includes 10 momentary switches for foot pedals.

As I move this to installation I am wondering what the best approach is for soldering or connecting the wires from the switches to the teensy.
Do I need to remove the pins and use the holes? Can i solder to the opposite side of the pins? Any other tools or parts needed ?

Any advice appreciated
Nick
 
One approach is to use a prototype PCB board. If you want a permanent connection, you can solder the Teensy's pins directly to the board, and use diagonal cutters to remove the extra pin length. Many of the PCBs act like breadboards in that rows of pins are connected. So you can attach the Teensy to one hole, and attach a connecting wire to the next hole, and attach this wire elsewhere on the board to where you want to connect the switches. Note, the better PCBs are double sided in that you can solder on either side of the board, while other PCBs are single sided where there is metal only on a single side.

If you can tolerate a little extra height and/or you want to be able to move the Teensy to a new board, you can use female headers that are soldered to the board and you just attach the Teensy to the headers. This is useful in that you can move a Teensy to a different set of headers (that might have different layouts, etc.). I tend to use this approach. I first attach the headers to the PCB, remove the Teensy, and then attach all of the wires, checking for connectivity with a volt meter (using the sound option to indicate that the two wires are connected).

You can solder wires directly to the pins or carefully attach a wire via solder to the top of the pin.

You can also desolder the pin and remove it, and then re-solder the wire to the hole.

For attachments to external buttons and switches, you can attach either male or female headers to your board, and then use female or male wires to connect to your device. I tend to like making dupont wire connections with headers for just the wires I need, using color coded wires for the various connections (typically red for 3.3v power, orange for VIN power, black for ground, gray for analog ground, blue for i2c SCL, green for i2c SDA, but the circuit doesn't care what colors you use).

You can attach wires straight to the PCB and then to the device, but I find that often times I have wires break, and I need to de-solder and then re-solder broken wire. So, I tend to use female headers to connect devices. That way it is simpler to change just the broken part, and if needed, I can move the device to the next board. There are various locking headers as well that can be used.

Here is my current project, which is a pair of LCDs running animated eyes from code I picked up from an Adafruit site using the smaller Teensy 3.2. This particular PCB has 15 rows of breadboard like connection (outer power rails, two sets of three rows of connection, and two inner power rails). It also has 10x3 pins on either side for connection. On one end, I have two headers for the two LCDs (one right angle, one straight up). On the other end, I attached the i2c pins and some analog pins to be able to be brought out, but I didn't attach female headers. I have since created a new board that now has 2 parallel rows of right angle headers for the LCDs, but I don't have a picture of it):
2017-11-12-13-00-010-uncanyeyes.jpg


I got the PCB from this tindie.com site. The first link, is a new version of the headers that have an optional set of mounting holes so you can attach the PCB to something else. The second link is a bunch of smaller PCBs that can be ordered. I have a 6x8 pin version of the PCB on the back of the Teensy to bring out A10 and A11. The third link is for a PCB that is big enough for a Teensy 3.5/3.6 (24 rows) that fits inside of an Altoids mint tin, and it allows you to break out various pins. The fourth link is for a larger board:

Adafruit has some perma-proto boards that can be used. The 30-pin boards are probably not as useful for the Teensy 3.5/3.6 since you only have 6 rows left over for connections, but perhaps it is sufficient. There is a larger board as well. The first board is the half-sized 30 row perna-proto board, the second is Adafruit's min-tin board with 30 rows, and the third is the full-size 60 row perma-proto board. You can buy them singly or in 3 packs. I generally buy them in multiples, because sometimes you get to the point that it is easier to start over, than un-soldering a lot of connections:

For male and female headers, I tend to go to the following sites. You can buy male, female, or stacking headers in various sizes. I like to have various sizes around (2 pin, 3 pin, 8 pin, etc.). You can also buy the 20 or 40 pin versions and cut them down to the appropriate size (use a rotary tool like a dremel to smooth off the rough edges):

In terms of dupont wire connection, I tend to like Pololu.com's setup that offers various number of pin connections, pre-made wire with male/female ends of various sizes, or crimp headers that you can make your customer connection. I find I prefer the pre-made wires to my own crimped connections, but I don't always have right sizes/colors on hand. Be sure to watch the video to learn about the system:

In terms of what you need, at a minimum I would suggest:
  • Soldering iron.
  • Solder wire (leaded solder is easier to work with, un-leaded solder is safer).
  • Copper braided wire to de-solder the connection.
  • Third-hand tools that hold the piece in place, and optionally provide a magnifying glass.
  • Consider a face mask and fan so you don't breath in solder fumes.
  • Lots and lots of patience, as you will need to practice, and a lot of times undo work.
  • Prototype boards.
  • Stranded and solid wire (typically 22AWG). Solid wire is better for PCB to PCB connections, while stranded wire is better where the wire needs to bend. I pick up packs with different colored wires, and color code the connections.
  • For de-soldering, I picked up a de-soldering iron that plugs in and it heats up the wire connection, and has a spring actuated pump to draw the liquid solder up into the unit.
  • Diagonal cutters.
  • Needlenose pliers.
  • Wire cutter/stripper (possibly part of the diagonal cutter or pliers).
  • Possibly head mounted magnifying glasses.
  • Volt meter that can do audible output to say when two wires are connected.

One thing that can be useful is to pick up a second Teensy, and connect one to the PCB, and leave the other in the breadboard. That way you still have the original Teensy for reference.

When possible, buy extra. I have multiple headers in various sizes, so that I can start work on the new project without having to wait for delivery of various parts, and when I'm running low, I put in an order to bring the order up to minimum purchase costs, and to reduce the shipping costs.

At a higher end, once you go past single PCBs, and want to make more than one do-dad, is to custom design your PCB that incorporates your wiring. I've not done this, but it is an option. I first saw this book by Simon Monk listed at Sparkfun, but you can also get it from amazon:
 
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Hi Michael
Thanks so much for your thoughtful and complete reply.
It is very helpful!
I had to read it a few times :)

Last night I went to Akihabara (electric town) in Tokyo and picked up much of what I need and wired the common grounds together..
I like the female headers approach and will try that.

I saw wire wrapping tools too... what are your thoughts on those ? Possible to wrap around the male pins, or are they too thick ?

thanks much
Nick
 
I never have done wire wrapping. Maybe somebody else can chime in.

Before you start your big project, it probably helpful to practice on smaller things, such as putting the buttons on external PCB's. There are various tutorials out there on how to solder (and de-solder) that you might want to check out. I don't remember what I went to when I was first doing it with an Arduino. That being said, while I've done it quite a few times, I still have to go slowly, and still have to de-solder pieces from time to time.
 
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I learned of wire wrapping from my EE buddy in1985 and before. It is effective. I've used some 30 ga wire and the wrapping tool on long header pins - then I solder it. True wire wrap pins are designed for proper good connection. I just took a standard male header and got a couple wraps with my tool that could then be soldered - without having to hold the wire and the solder and the iron at the same time. When you have the pin length and a small wire will do it saves burnt fingers - and allows stacking wires as needed too. It was partly how I built my first ILI9341 to T_3.2 display board.
 
I saw wire wrapping tools too... what are your thoughts on those ? Possible to wrap around the male pins, or are they too thick ?

Wire wrap tends to only be reliable when using the proper #30 size wire wrapped on 25 mil square pins with sharp corners. It usually works for quick prototyping on round component leads, but time, temperature and any mechanical stress will play havoc with wire wrap on pretty much anything other than 25 min square pins.

You earlier asked "As I move this to installation". If that means you intend it to be long-term reliable, I'd suggest avoiding wire wrap unless you only do it with square pins meant for wire wrap.
 
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