Regulation

I have decided to go with a single 12v power supply instead of the dual 5v / 12v I was using. I needed a regulated 5v for the Atlas Scientific sensors so I rolled it all into on. The 12v goes into the control board and thr CPU can take the 5v Vcc from there up the 15-Way D-Sub. I've still got a problem because added the temperature sensor means I need 16 channels! So I'm going to have to think my way round that. Worst case I shall use the shell of the D-Sub as an extra pin and link that to Gnd.

I've added the 5v regulator to the board. I don't know how many amps I will be drawing to run the semiconductors. I hope it's not much because it is that current times approx 7v that I will be dumping out of the regulator. The regulator is maxed at 1.5A anyway so at most I will be dumping 10.5W and only consuming 7.5W ! I'm pretty sure that 1A is unlikely. If it becomes an issue I can go back to split supplies but I bet they do the same. The light I want to use for a 3ft sqr grow is 250W so it's a small proportion. Perhaps I can water cool it :)

Here's the circuit without ICs and just a regulator

I have tested the 5v rails and they are registering 4.9v on the multimeter, unloaded. My Multimeter is cheap so I don't know if it is out of calibration or the regulator is only producing 4.9v. No matter. It is more important to have a constant voltage than an exact one.