How to use a Weller DSX80 with a WSD81 soldering station

Recently Рwhile browsing eBay РI came across a Weller DSX80 desoldering iron.  Below I will describe extensively how to use the DSX-80 without buying the expensive soldering station that you are supposed to use it with.

The WDD-81V

The WDD-81V

This German beauty uses a heated tip with a hole in it through which a vacuum is pulled by pushing a button. This allows you to desolder through hole components effortless. It can be found on eBay for around 80 euros.

Frustratingly the accompanying soldering station¬† (The Weller WDD-81V) cannot be found cheaply online. This station uses a compressed-air inlet, a Venturi effect vacuum generator and a solenoid valve (controlled with the button on the iron) to switch the vacuum. It outputs it’s vacuum through a little connector below the 7 pin connector.

Weller WSD-81

Weller WSD-81

However, the Weller WSD-81 is very abundant on eBay and relatively cheap (about 60 euros). It uses the same 7 pin proprietary Weller connector, thus it can deliver enough power for the DSX-80. If you connect the switch on the iron to a solenoid valve connected in between an external vacuum source, you have a fully working DSX-80, for a fraction of the retail price. Easy, right? That’s what I thought when I had this idea in my mind. It turned out to be quite challenging. Read on below to see what things I decided to use to emulate the WDD-81V, and how I connected everything.

In order to make this work with the WSD-81 we need to figure out these things:

  • What vacuum source
  • How to switch the vacuum on and off
  • How to use the button on the iron
  • How to integrate all this

The vacuum source

Because air compressors can be a bit expensive, large and noisy, I decided to use a vacuum pump. I thought about salvaging the compressor from an old refrigerator, but then I came across the Aoyue 933. It is marketed as a solder fume absorber, but it works just fine as a cheap vacuum pump. It’s cheap price (35 euros) made me choose it over fooling around with a refrigerator compressor. It provides about 0.8 bars of vacuum, which is the same as what the WDD-81V provides.

Aoyue 933

Aoyue 933

But you are free to use any way of generating a vacuum you want (venturi vacuum generator (commonly called ‘ejector’)/ old pumps/…).

 

Ejector

Ejector

A way to switch the vacuum on and off

I used a 12V DC normally closed solenoid valve with 1/4 inch to barbed adapter to connect to hoses. Find one like this on eBay:

Solenoid valve on eBay

Solenoid valve on eBay

A way to use the button on the iron

Below is a picture of how the button is connected in the handle of the DSX-80. I couldn’t find any schematic of the controller board.

The schematic of the handle and the pinout of the 7 pin connector

The schematic of the handle and the pinout of the 7 pin connector

As you can see, pin number 7 is either connected to ground or pulled down through a 44k ohm resistor. There is no way to use this switch directly.

I soldered 2 wires to the pins on the controller board to see what the button does.

The wires soldered to the pins

The wires soldered to the pins

Putting any voltage on pin 7 will offset the ground of the controller board inside the WSD-81, which results in incorrect temperature readings. I measured the voltage at pin 7, with pin 1 as ground. It’s about 5V when not pressed, and 0V when pressed, drawing any current from pin 7 will collapse the voltage. I tried to directly switch a P-channel MOSFET with that voltage but it didn’t work, it drew too much current, which caused the gate source voltage to be too low.

So I needed something that inverts the signal which is presented on pin 7 (because the relay is normally closed), and has a high input impedance, a CMOS inverter IC! I came up with this circuit, using an old school CD4049UBE.

The schematic

The schematic

VIN is sourced from the large input capacitor of the onboard 5v regulator of the WSD-81.

Sourcing VIN

Sourcing VIN

After some testing on the breadboard I made the final circuit on some perfboard, and added some screw connectors:

Finished perfboard circuit

Finished perfboard circuit

The incoming wires are (from bottom to top) the switch signal (pin 7), ground (pin 1) and +16V unregulated (from the onboard regulator). On the left the solenoid valve connection.

Integration

I choose to put the solenoid valve and my perfboard circuit inside the vacuum pump. This way I can easily tap into the internal tubing to connect the valve in between. In order to connect the WSD-81 to the vacuum pump, I used some 5 pin DIN connectors I had laying around from an old project to make a sturdy connection. I drilled a hole in the bottom of the pump to mount the solenoid valve, and I hot glued the perfboard to the back of the front panel of the pump.

Below are some pictures of this:

6 Comments

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  1. good idea

  2. Hi,
    thanks for this article.
    I will try to apply a similar circuit to my WD1.
    On the vacuum side, I plan to use a different compressor (not sure which one yet) and an ‘expansion barrel’ as buffer with a sensor to turn the pump on/off and a solenoid to turn on/off the vacuum. This way I hope, the pump doesn’t have to be running all the time.

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