1
Project development, ideas, and suggestions / Custom Weller WSM 1 style controller for RT series tips
So far I've gotten hold of an RT8 tip for the Weller WSM1 and similar controllers. I'm trying to build my own small form factor controller for these tips. A simple controller that can fit inside the barrel of the soldering pen handle is my aim and using a couple of buttons and some LEDs to show temperature in increments of 25degC. I plan to use a micro controller in order to control the thing and run it off a small laptop supply.
First of all I need to figure out how this tip works. There is a headphone style connector on it that I've read the following resistances:
The three conductors I'll refer to as TIP, MIDDLE and SLEEVE.
TIP conductor is not to be mistaken for the physical soldering tip of the iron, I can't help but use them interchangeably...
The SLEEVE conductor is a hard connection to the entire barrel of the soldering tip. The black rubber grip is also conductive.
So far I've determined this:
I have no idea what's between the MIDDLE and SLEEVE, I initially thought it was a thermocouple but I don't read anything useful off it.
In fact I read strange voltages and resistances out of it when I connect the supply to the heater. ranging from a few mV to a couple volts.
This leads me to believe there is some connection between the TIP and MIDDLE??
I used a DC bench supply to power the heater incrementing up in 1V steps and logging the temperature. I can get the soldering tip up to 300deC (as measured by holding a temp meter against the end of it) with 4V 2A (8W) input. I tried soldering with this set at 8W and saw no fluctuation in voltage or current as the iron cooled then heated again.
I put 4W into the MIDDLE conductor again referenced to the SLEEVE conductor and got nothing useful at the soldering tip in terms of heat. If anything, the barrel heated up...
So I cracked open the soldering tip and found this...
The SLEEVE is connected to that thin tube that I chopped off from the soldering tip to get the barrel off. Inside the thin tube were two wires:
Each is insulated in heat proof material however the conductors inside seem to be of different material. My meter didn't note anything very different about them in terms of resistance/length but then again, I have a cheap meter that barley measures down to 0.1ohm.
This tip is meant to be 12V and 40W rated but I haven't dared put 12V across it as it would exceed 40W unless I limited the current. I'm also guessing that the tip should only receive 40W for a short amount of time to crank it up to working temperature, I can solder fine with it running off 8W of power however takes about 30seconds to heat up.
This tip is also designed to be ESD safe where the SLEEVE conductor would be referenced to ground via a large resistor? If the heater is actually between the TIP and MIDDLE, surely there would be a voltage on the SLEEVE.
I've had another person who has these tip and the WSM1 station confirm they have the same resistances between conductors and their tip is working fine.
Any ideas on what kind of pinout this thing has?