Hi Eric,
A whole bunch of things.
1.) Cannot extract the file under Winzip it tells me it is invalid?
2.) If I try interpret the graphs.
- V(thntc) is low so Q1 and MOC3081 goes high. Current flows for a period of ~95 milliseconds before V(thntc) goes high.
- V(thntc) goes high, the rest goes low and current no longer flows for a period of ~110 milliseconds.
So the switching rate is roughly every 100ms to maintain a temperature that will correspond with the combined resistance of R9 and R10 =14.5k which is a temperature of 2.5°C?
3.) Although 2.5°C is the required temperature at the crisper area of the fridge the measurement is taken from the evaporator unit which is cooler by what appears to be 8°C based readings taken. That means V9 and V10 will need to total in the order of 25k in order for the the evaporator to be at -7°C so that the fridge can be at a max of 1°C. So when I play with LTS the two pots will change to 25k and 5k?
4.) The way I understand it the MOC3081 is basically a low power SSR?
5.) If I look at the latest schematic you sent, R5 appears to be the 175W heater, the value of 350 Ohms confused me?
6.) As the MOC3081 is able to cope with 1.2A this should be fine to drive the 0.8A of the heater. I did notice a caveat on the data sheet "The optoisolator should not be used to drive a load directly. It is intended to be a trigger device only". Does than mean we need to add the Triac as per the data sheet? That would also allow me to drive with the freezer on.
7.) The old circuit was not the best I do understand but theoretically I had the hysteresis such that the on and off voltage were 6.39V and 6.25V, thats tight. Why then was the relay not chattering away as the unit switched on and off. Have any idea?
8.) It is OK for the 12V to share a common ground with 220V?
You are going to need that holiday after all the work you are doing for me
.
Cheers
Andrew
PS: Are you familiar with chemelec's inverter,
**broken link removed** I did the revised circuit. Is this OK for my heater supply.