Monday, January 30, 2012

High Sleeper cabin bed lights - The Circuit mk1

This post in the continuation of a series, starting with part 1.

When you're starting something new, especially in electronics, it is always a good idea for your mark 1 version to be as simple as possible. This is especially true when working with a new tool chain, new programmer, and you don't have any debugger at all [1]. Consequently, this version does not have any input controls and it only drives one 5mm LED, rather than the full strip shown previously.

So, here's are mark 1 circuit:

Circuit Diagram for The Circuit Mk1

Saturday, January 28, 2012

Hand soldering SMT packages to stripboard

Prototyping a new design can be tricky enough, but it can get even more so when the part you want to use is not available in a through-hole version. I needed a p-channel FET to run the high side switching of an LED matrix and they did not exist in a sensible package, so I made one.

Now this makes me proud - i fear no package!

Hand soldered SMD transistor package on stripboard

This is a Rohm P-channel MOSFET (RTQ030P02) in a TSMT6 package. The black package body is 2.9mm by 1.6mm.

The process to make this little guy is pretty straight forward, although kinda fiddly.

Friday, January 27, 2012

LED encapsulated in hot melt glue

In a future project that I'm working on right now, I need to fix some standard 5mm LEDs into 6mm holes through an 18mm thick sheet of MDF. The final idea is to drill the holes all the way through the MDF and then cover the front with a 0.6mm birch wood veneer, sliding the LED all the way through from the back and fixing it in place with a hot glue gun.

Now, this got me thinking. How are the LED packages, which are rated for 100-125 degrees centigrade, going to handle the 200 degrees of hot glue? An experiment was in order.

5mm LED encapsulated in hot glue pt1

5mm LED encapsulated in hot glue pt2
It lives!

Right, that's enough work displacement for the moment - now I've got to get back to working out why my AVRISPmkII refuses to talk to my ATtiny44v.

Thursday, January 26, 2012

First contact with an MSF receiver

Back in May last year I wanted to play with an MSF receiver, so I went and bought one from PV Electronics. This first video is just powering it up for the first time after connecting the wiring loom and antenna. The LED shows the raw MSF datastream that is being received. (The TO-220 package you see at the beginning is a good old faithful 7805 voltage regulator.)

A few weeks later, I was prototyping it out and hooking it up to an Arduino UNO. I had a TLC5916 LED driver chip hooked up and running an 8 bit binary count on the LEDs you can see. If you look at the indicator LED on the receiver board, you can see that something isn't quite right.

Something is generating RF noise in the 60kHz band (which is perfetly acheivable by the components on the board). You can see that, depending on the orientation of the ferrite antenna with respect to the breadboard, the noise comes and goes.

I'm not sure whether this was because of the the long curving wires from the Arduino Uno to the breadboard acting as an antenna; or if it is because of switching noise from the TLC5916 as it drives it's output FETs with the PWM train.

In those infamous scientist words, "More research is required"