Update on the Switch Box project...


I have been trying to stay focused working on completing the switch box. I find that if a project takes too long for me to complete, I start to lose interest. However, in this case I believe this piece of equipment will be well worth the all the work. It is unique as I have not found anything commercially available that can perform the function of this project.

I have completed wiring most of the front LED's, except for those in the timer circuit, and performed the "smoke test." Well none of the smoke escaped and all the indicators functioned as expected. I also installed all of the connectors on the back panel and installed the board for the timer/audio circuit.

However, during my assembly I ran into a problem with one component, the main switch. In wiring the front panel, I noticed that I mistakenly choose a main switch that was designed to work with 120V AC, not 13.8V DC, this posed a slight problem that the LED in the switch would not light if used with DC. The switch came from my local Radio Shack but they did not have a switch of the same type and size that would work on DC, and I did not want have to go on a hunt to find a suitable switch. I was left with no choice but to disassemble the switch and convert it to work on DC.

In opening the switch, I discovered that the LED was being powered by the source in series with a SMT diode and SMT resistor, since the box runs on 13.8 volts DC, it was just a matter of bypassing the diode bridge and changing the resistor to drop the voltage/current to the correct amount. On the Internet, I found a calculator which determines the correct resistor to use with the LED. The calculator suggested a 680 ohm resistor. However, this resistor let the LED glow too bright. I ended up installing a 2.2K resistor which provided just the right amount of illumination.

Here are a few photos of the modified switch and the current progress on the switch box.