You're further along than I am. My ultimate goal is to deploy a sensor/control system in my cold frame that will allow me to measure the basics (temperature, humidity, light, soil moisture) and minimize the temperature swings by controlling a small space heater and an exhaust fan. I've gotten as far as deploying solderless breadboard prototype 0.1 to monitor temperature and humidity and transmit the information to a RPI for logging . To measure light, I would use a sensor that has a logarithmic output. Adafruit has one for $3.95 http://www.adafruit.com/products/1384 which is probably less expensive than starting with a dollar photocell and building/tweaking your own log amp. I've not had much luck with sweet peppers either, they seem to require a very long growing season.
Ordered a couple of those Sensors just this moment. I'm having much better luck listening to everyone's good advice rather that bumbling through it myself.
I did some ( A Lot ) of reading last night on growing Peppers. First thing that was said was never use peet pellets. Or peat period! Peppers don't like it. I've had such good luck starting other vegetables in those peat pellets on my kitchen window sill I never thought that would be an issue.
http://www.ecoseeds.com/Pepper.growing.tips.html Doing a little research last night came up with a company right in my town. They had lots of tips. I love roasted bell peppers, and want to can my own so that I'll have them all year. I've got friends who have them coming out their ears and they are only 10 miles away from me. I think that it is even colder in San Mateo than here in Redwood City. I've a south facing wall that is painted white. I've decided to put a couple planter beds right there and see what happens. I'll be placing another Moteino there as soon as those sensors from Adafruit show up.
I've never done a cold frame before either. I think you are way ahead of me. That looks like it might be a good way to keep the heat up. I'm just really worried when, or if Summer ever gets here it would be too much. My backyard gets to 100F. A lot of people I talk to say that my Greenhouse will be too hot. I'm planning on having a curtain system that will move to help control temperature. But I'm no where near any of that yet. First I have to complete the Green House.
Thanks for the input. Let you know if I stumble on something that works with the Peppers.
Mab