Recovering components from old PCBs

03. July 2014 · 1 comment · Categories: Electronics · Tags: , , , , ,

I was watching some videos about making PCBs using solder paste and ovens to reflow the solder, and I wondered how easy it would be to remove components in a similar fashion. What to use as the heat source?  A hot-air gun/paint stripper.

I had an old compact flash card reader that's been sitting in a draw for years, so I thought I'd use that as my first victim/experiment.

20 minutes later I have a bunch of random components, which may or may not be of some use at some point (Edit: I found a use for some of the SMD resistors in the other word clock I'm making), but hey – it worked:-

Components removed from PCB

Voila; a bunch of random components. There's some octal flip-flops, resistor arrays, SMD resistors, through-hole transistors, smd transistors and diodes, a couple of large capacitors and other bits and pieces.

Component Haul

The heat gun I have has two settings; I used the low setting, which is about 350 degrees C. The high setting is about 600 degrees.

I clamped the board upright in a vice and found that the larger SMD components just fell off as the solder melted, whereas the smaller components I had to pick off with some tweezers.

This particular board is a 4 layer board and I found that the through hole components took a minute or so of heating before the solder melted all the way through enough for me to pull the components off. I also tried this on an old PS/2 ball mouse PCB, which was just a double sided board, and the through-hole components on that came out much easier.

Only disappointing thing is that SMD capacitors don't have any markings on them, so you don't know what their capacitance is. How easy is it to make a capacitance meter?

LED Cubes

24. June 2014 · Write a comment · Categories: Electronics · Tags:

I thought I would have a go at making an LED cube.

I had some 4017 decade counters, so I was thinking about making a 10x10x10 RGB cube. From a numver of other LED cubes I've seen, the way that they do it is to provide power to all of the LEDs in every column that contains the LED to be lit, and then ground the plane containing the LEDs to be lit. If I wanted to have a 10x10x10 RGB cube, that would mean I would need 300 lines for the LED anodes, plus 10 for the cathods (assuming common-cathod LEDs).

It occurred to me that maybe you could do it another way; join all of the LED anodes together in a plane, and then ground each column. This way I would only need 30 lines for the anodes, plus 100 for the cathods.

I thought I would try a simple one first using this method; a 3x3x3 mono LED cube. I also thought I'd try some hardware that I haven't used before; an Arduino UNO.

3x3x3 Mono LED Cube

3x3x3

Word Clock

21. March 2013 · Write a comment · Categories: Electronics, Hardware, Microcontrollers, PICAXE · Tags:

Was bored, so decided to have a go at making a Word Clock.