The Loft Datacenter: III

The extension lead had been cut previously and was bodged together with a terminal block. Fitting the IEC 60320 was a matter of removing the terminal block and fitting the C14 connector. Then taking it off again once I had measured the distance from the shelf to the rear of the UPS.

So back to the other piece of cable on the other side of the terminal block which was of the right length. Using this cable would mean opening up the extension box to swap the short cable for the longer piece. While doing this I decided to replace the burnt out neon indicator lamp as the light switch under the new shelf is quite shadowed and it might help shed a small amount of light into the area. After a bit of searching I decided to use components from Maplin, which is local, that could be had for the princely sum of £0.93 plus P&P.

The circuit is a simple one (simple enough for me to understand!). By Kirchoff's 2^nd law the high value resistor (ballast resistor) takes most of the voltage. I would have liked to work out all the values but a query to Maplin on the max working current and voltage of the neon lamp fell on deaf ears.

I also looked at fitting an LED instead of the neon lamp as the lifetimes of LEDs are 50,000 hr as opposed to neon at 20,000 hr. Although you would not expect an LED to work with AC, it will light on the positive phase of the cycle and as long as the negative phase isn't greater than its maximum reverse voltage it won't be damaged. But the current draw of the LEDs was too great meaning they would need to be coupled with a large high wattage resistor. There are ways to get round this but I opted for simplicity.

The Maplin site actually specified a ballast resistor to use with the lamp at UK mains voltage. But for my own personal edification I checked it out as well. As usual Wikipedia had the required information and I made a little spreadsheet to help with looking at using LEDs.

The resistor came with more bands than I am used to but I found a neat colour code reader that confirmed that I had the right part.

A small amount of soldering later and all done. The final stage is to put the extension bar and the rest of the IT into place.