Wire to Board matching for re-solder

[jamesrmaher]

To be up front: This is a question unrelated to your code, but I would gladly buy you a coffee or beer in exchange for some help.

The work you’ve done here is super impressive. It’s also the only place where I have found more info on the Jarvis handset internals.

Long story short: my handset cord was unfortunately ripped out of the handset. So now the desk is not controllable. I have the board taken out of the handset, and the wires from the ethernet(?) crimped and ready to re-solder to regain control.

The question: Which wire goes on which socket? I have a red, red/brown, white, transparent and purple wire. The board has LED, M1+, M1-, 5V, GND. Do you know which wire is for which socket? Thanks in advance

[phord]

Bummer! Is this the "Up/Down" controller? I'm not sure what the "LED" pin would connect to. There's no signal on the interface that makes sense to me for that one. Also, the purple wire is very short. Maybe the LED pin was never connected to a wire?

Do you have a multimeter and a soldering iron?

If the "ethernet" RJ-45 connector is the same as mine, then you can find the wire purpose using the continuity test feature of your multimeter. Use this diagram to identify the pin numbers (Ignore the wire colors on this diagram.)

I assume M1+ and M1- are the Up and Down buttons, respectively. I have no idea what the LED is for. But if I'm right, then M1+ should go to HS1 and M1- should go to HS0.

Using this assumption, here's what I would do:

1. Touch the meter to pin 3 of the RJ-45 connector.
2. Touch the other lead from your meter to each of the loose wires until you find the one that connects to pin 3 (beep!). The one that goes to pin 3 should be GND.
3. Next, find the wire that goes to pin 5. This should be 5V.
4. Confirm that you didn't get the pins backwards by measuring the voltage from the desk when the wire is plugged in.
   a. Set the mulitimeter to measure DC Voltage.
   b. Touch black to GND and red to 5V.
   c. If it shows 5V (or close to it), then you were right! \o/
   d. If it shows -5V, you got the backwards. (This is also a win. yay!)
5. Continue like this to find the M1+ on pin 6 (HS1) and the M1- on pin 7 (HS0)

If yours isn't wired like mine, then you have some sleuthing to do. Again, I would do this:

1. Find the ground wire. One of these 5 wires is the signal ground. With the cable plugged in to the desk, use a multimeter to measure the voltage between the 9 pairs of wires (white-red, white-purple, white-clear, white-pink, red-purple, red-clear, etc.). You should find 5v between several of the wires and the ground one. The ground will be the zero-volt wire.
2. Identify the power wire. This may be harder because probably 3 or 4 of the non-ground wires will show "5v" when you test with the ground wire. If you have a resistor handy (at least 100 ohms), use it to connect one of the wires to ground. If the desk moves down, that's probably M1-. If it moves up, that's M1+. If it doesn't move at all, that's either 5V or LED.
3. Identify 5V line. Using the current meter (ammeter) on your multimeter, you can measure the current through your 100ohm (or whatever size you have) resistor. To do that, you'd connect the ammeter ground to the identified ground wire. Connect the ammeter positive (or load) to the resistor. (Note: this might be a different connection than you use for Volts on your multimeter). Then touch the other resistor leg to each of the unidentified wires in turn. The one that passes the most current through your ammeter is going to be the 5V wire.

The last wire is still a mystery to me. Does it connect to LED? To something else?

More notes: If you want to confirm what M1+ and M1- do, you can test the board itself. Try pressing the Up button while measuring the continuity between the M1+ pin and GND. If I'm right, pressing Up should cause M1+ to connect to GND, electrically. I think this will work without any power on the board at all. Repeat this with the Down button and M1-.

What about LED? Still no clue. Maybe you can find some ideas by testing continuity between that pin and other solder "pads" on the board.