On Wed, 19 Feb 2014 17:27:03 +0000, Adrian Brentnall wrote:

Hi Folks

Still working on that DIY glass kiln -
done all the nasty itchy stuff (it's lined with ceramic fibre -
think fibreglass roof insulation & then some!)

So the kiln controller is powered by AC, from a 12 - 0 - 12 v
centre-tapped transformer - which is half-wave rectified on-board the
module to give +12v.

My other bits of circuitry (the thermcouple conditioner and the famous
latching relay / logic module) wants 12v dc, plus a stabilised reference
voltage in the region of 10v. Will add suitable c's to take any relay
switching spikes off the 'instrumentation' dc line.

Both modules share the same 0v line.

Can anybody see any snags in running all the electrics from the same
centre-tapped mains transformer (it's got sufficient current available)
- simply by adding another half-wave (2 diodes) circuit, smoothing cap &
so on...
- see diagram here http://www.ambquality.co.uk/power-supply.html

I had bought two c/t transformers, but if I can get away with just one
then that frees up some space in the enclosure.

Thanks Adrian

From a basic electrical view it will work fine. Just make sure that all
coils are suitably suppressed - you don't want back-EMF spikes flying
round when they open.

(Note that using a full-wave rectifier system like that the DC current
available from the transformer is equal to the AC current rating, so you
may have even more spare capacity than you expected. )