Recently – while browsing eBay – I 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/…).




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.


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:

The PCBs arrived two weeks ago from the fabhouse. They look great and professional and are of good quality. However I can already spot some design mistakes that I’ve made, and can think of some improvements:

  • Some vias are too close to solderpads.
  • The Bosch BMP180 appears to be hard to get your hands on, so I am thinking of going with another sensor, like the MPL3115A2, which is widely available.
  • I’m thinking of putting the LCD on the back of the PCB, but I like the flush backside I have now.
  • Switch to using 1206 smd resistors instead of 2010. I thought it would be easier to solder, but 2010 resistor appear to be hard to get. 1206 are more common.
  • Originally I wanted to use a ~2500 mAh LiPo batter, but those too appear to be hard to get, so I’m considering switching to using 18650 lithium batteries, they are easy to get (ebay is full of them) and there are easy PCB mount available. Thus solving the problem I had with mounting the lipo to the pcb.
  • Use one pcb layer as ground, this will cut the amount of traces in half, and will need less vias. It will also decrease the ground resistence and increase the current handeling capability, which is a good thing.
  • Use the auto router less, the traces look terrible.

So these points will probably be the improvements to v1.1 of the pcb design. I have not tested the PCBs yet, because I’m waiting on some components to arrive.

Today I added some features to the circuit, a latching push button on/off and backlight switch. The on/off button is connected to the enable pin of the LDO. After I finally finished the circuit I started on the board design, which was something I had never done before. But with some help from the autorouter I finished it quite quickly. Then I’ve sent them over to pcbway, who made 10 boards for 20 dollars inc shipping. Now it’s time for the waiting game.

files (sch, brd and gerber (.zip)):

Arduino Thermometer


Today I came a long way designing the circuit for the thermometer project. I found out that powering the atmega328p-au directly from the vbat pin of the charge controller wouldn’t give a lot trouble, but other components were a bit more picky. So I opted for a LDO voltage regulator (MIC5219-3.3v), which has a low dropout voltage and even works as a dc-dc upconverter! Sadly the datasheet is not very extensive on example circuits, but I guess the battery voltage is stable enough so support circuity is not really necessary.

I mostly used the Sparkfun eagle libraries and I looked at some breakoutboards from adafruit to see how they hooked things up. It’s released under the Open Hardware and CC Share Alike 4.0 licenses.

Now I’m going to check the circuit a few times, and then I’m off to prototyping on the breadboard and designing the pcb.

Here are the files:

Arduino Thermometer (.PDF)

Arduino Thermometer (.SCH)

After brushing up on my eagle skills, I almost completed the design for the powersupply for the thermometer project. It uses the MCP73831 charge controller, hooked up to the usb connector and to the battery. I’m not shure if I can hook the Vbatt pin of the chargecontroller directly to the atmega’s Vcc pins, but we have to find out I guess.charger

Yesterday I did a lot of research online on available components and I came up with the following components and functions.

Name Description Adafruit Datasheet
DHT22 Temperature and humidity sensor link link
Bosch BMP180 Barometric pressure sensor link link
Microchip MCP73833 Charge management controller link link
Display Generic 16×2 character LCD link link
Atmega328P-AU 8-bit-AVR-Microcontroller TQFN package link link
Lipo battery 2500mAh LiPo battery link link


The thermometer should incorporate the following functions:

  • Display absolute temperature in degrees Celsius, at 1 decimal point resolution (maximum resolution according to the datasheet)
  • Display absolute relative humidity in percentage, at 1 decimal point resolution (maximum resolution according to the datasheet)
  • Display absolute air pressure in hPa (mbar), at 1 decimal point resolution (can do up to 2 according to datasheet, but it’s not necessary and takes up valuable space on the lcd)
  • Display battery percentage left, at 0 decimal point resolution (measuring battery voltage with the adc, using onboard 1.1v reference)
  • An ability to turn the device on and off with a push button
  • An ability to turn back light on and off
  • Operate from battery and mains
  • An ability to charge with a standard phone charger with micro usb port
  • An ability to use a ICSP programmer to upload new sketches

I’ve linked the adafruit breakout boards for most of the components, but in the end product I will just use the chips and support circuity. It’s convient to look at the adafruit pages because all the information is located in one place.

Featured image By Fabian ~ (Fabian R at de.wikipedia) – Own work, CC BY-SA 3.0,

I have been into electronics for a long time now and always had the desire to built one of my designs on a pcb. And with cheap pcb prototyping services from China that has become very easy and cheap (about 30 usd for 5 boards). I want to make something usefull aswell so I decided to start off with something simple, a thermometer. Much like the one I made on a breadboard a while ago. I do want to use a bigger display though. In order to get this done I have to take the following steps:

  • Stating exact functions of the thermometer & choosing components
  • Coding
  • Designing the circuit
  • Prototyping on breadboard
  • Designing the pcb
  • Assembling pcb and testing
  • Designing an enclosure (3d printed or wood)
  • Evaluation

The project will be entirely based upon open source hardware. I will try and log my progress as I get along with this project. If the project is succesfull I might sell the remaining boards as a kit, with detailed instructions.



I have been working on a Quadcopter for about a year now, but about half a year ago I lost motivation for the project. Now finally found some motivation to continue with the project. I started it because I really like everything with a remote control and lots of electronics in it xD. Also it was a lot in the news a year ago, with all the NSA and army things (civillian surveillance, remote attacks). The original plan was to make a drone as cheaply as possible, while also having a lot of opencource hardware/software, so no DJI controllers etc.

Rightnow have the following things complete:

  • Frame (found it on ebay awhile ago)
  • Flight controller (MultiWii PRO 2.0 from
  • Remote Control (Turnigy 9x)

I chose the MultiWii because it is Arduino based, and if you didn’t know, I LOVE arduino. It’s modular and easy to understand, and yet powerfull enough for most tasks. I chose the Turnigy basiclly only because everyone uses it (lots of info) and you can upload your own firmware to it.

That leaves the following things to be bought/ done:

  • Motors
  • ESC´s  (Speedcontroller for the motors)
  • Propellers
  • Battery + charger
  • Power distribution

The second list lists also the most expensive parts of a quad build, probably about 100 euros (150 dollars). And it is the most work.

In the future I would like to add FPV and GPS location fixing.

Good links for building a quad yourself are:

DIY drone

Normally the lab is this cold harsh place, mostly due to the TL lighting. But today while I was testing my leds for my 4x4x LED cube, I turned the lights down and it looked real cosy with the red lights (on the run)

With the red leds:

leds testing

Normal lighting:


Will be updating soon on my ledcube.

I recently came across a bargain on Marktplaats (Dutch Craigslist), a Dell PowerEdge 2950 II with 4* 1TB HDDs. This was a no brainer. Buying the disks alone would cost equally as much. Picked it up a few days ago and the server is running VMware ESXi 5.5. I currently have set up FreeNAS as a VM, it’s running SABnzbd, couchpoatato and sickbeard. I’m planning to make some more VMs to run a VPN and do some backups, but I need to upgrade the CPUs and RAM for that. Right now it only has a dual core xeon x5100 @ 1.8ghz and 5GBs of RAM. The CPUs and RAM are dirtcheap on eBay.

Dell PE2950