Part One I’ve just moved back to University for my final year, and as such have found some time to draw up half of the schematic for the rugbyPICclock! I was pleased to find that as soon as I arrived in Bath, I plugged in the clock, it received the signal fine and was displaying the time in no time.

Shown above (click for a big version) is the schematic for the digital part of the circuit. This schematic has four inputs, Mains Live, Neutral and Earth and the digital signal input from the receiver. A common cathode 6 digit LED display is connected to the MAX7219 in the schematic. Exact details on how to go about connecting the display up to the MAX7219 are given in the datasheet.

Note that if you are building this circuit you should be very careful when dealing with the mains parts if you don’t have experience, you could really seriously injure yourself. As an alternative to the power supply, you can buy a 12v DC power supply (or use a 12v battery) and connect it to the ground and input pins of the 7805. You should bear in mind though that the receiver won’t work as well if the 0v isn’t connected to mains earth. Thinking about it, connecting the mains earth to the low voltage parts of the circuit probably goes against some kind of wiring regulation. The general rule is fairly obvious, just don’t touch mains parts in the PSU when it’s on. That way you’ll live. :-)

I tried for ages to find a decent free program to draw the schematic in a pretty fashion, but couldn’t find one so in the end resorted to drawing it (messily!) by hand.

I’ll post up the PIC code soon (or can email it to you if you mail me), because it’s still a work in progress. Losing my PIC Programmer power supply in the Cheltenham to Bath move doesn’t help.

Just as an aside, I’ve now confirmed that the clock receives a signal and works fine in Cheltenham, Bath and Stevenage, all in the south of England.

I’ll get to work on the receiver and demodulator schematic. This is nowhere near as simple as this schematic though, so it may take a while.

3 Responses to “PSU / decoder: schematic part one”  

  1. 1 luke

    If you want a good schematic editor, and PCB layout editor, try eagle CAD, by CADSoft.

  2. 2 andy

    I’ve since discovered that, and it is good yes. Wish I knew about it at the time!

  3. 3 Dermot

    You should be fine, connecting the circuit ground to earth because it’s isolated by the transformer. Make sure the transformer isn’t the “auto transformer” type, with one of the primaries connected to one of the secondaries, or you’ll trip the RCD (probably).