I need a control to be able to adjust the heat applied to a boiler. I have a 100 gallon boiler powered by 3 4500W, 240v immersion heaters. I need to be able to heat the boiler up quickly, but then back off the power to a yet undetermined level. The power level will change depending on several factors, so I didnt want to use a thermostat. Im using a 6475AXXSZS-DC3, 75A zero cross SSR and a heavy wall wart DC 12v 1A to power the circuit.
I found a schematic on the internet and planned on using this when the boiler was completed, which it is now. I have spent the last week immersing myself into electronics and was able to build this board, but it only varies the duty cycle down to 50% and thus is not low enough. I did make one change to this schematic; I changed the 4.7uf to a 1uf, which lowered the pulse frequency to a lower and more acceptable level. Other than needing a big heat sink on the SSR and the 50% problem, the circuit works great on the boiler.
I had read on one of the pages here that one could change the duty cycle down to below 50% by changing a resistor between pin 6 and 7, but I couldnt figure that out even after switching out the 1K resistors with several others up to 33K.
Im also considering using all 3 heaters to initially heat the boiler and then using only one heater to keep it hot enough, but this does not solve my problem. 50% is still to hot using only one heater. Im trying to figure out a way to safely switch from 3 heaters at full power to one heater through the SSR. Using a dedicated circuit breaker box with a 60A breaker and a 20A breaker might work well.
My back is against the wall on this one. Im opening a distillery and I should be spending my time perfecting my vodka and rum recipes instead of learning electronic theory. Everything is ready to go except this one small but crucial piece of the puzzle.
If someone could provide me with an easy to understand schematic, it would be deeply appreciated; or even a way to modify the circuit that I have already built. I dont understand all the talk about saw tooth and ramp wave form, but I guess these are the theories that influence what I need. I already have a 556 and two 555s so a schematic that incorporated what I have would save me a week by not having to order different parts.
Please help me. Thank you.
I found a schematic on the internet and planned on using this when the boiler was completed, which it is now. I have spent the last week immersing myself into electronics and was able to build this board, but it only varies the duty cycle down to 50% and thus is not low enough. I did make one change to this schematic; I changed the 4.7uf to a 1uf, which lowered the pulse frequency to a lower and more acceptable level. Other than needing a big heat sink on the SSR and the 50% problem, the circuit works great on the boiler.
I had read on one of the pages here that one could change the duty cycle down to below 50% by changing a resistor between pin 6 and 7, but I couldnt figure that out even after switching out the 1K resistors with several others up to 33K.
Im also considering using all 3 heaters to initially heat the boiler and then using only one heater to keep it hot enough, but this does not solve my problem. 50% is still to hot using only one heater. Im trying to figure out a way to safely switch from 3 heaters at full power to one heater through the SSR. Using a dedicated circuit breaker box with a 60A breaker and a 20A breaker might work well.
My back is against the wall on this one. Im opening a distillery and I should be spending my time perfecting my vodka and rum recipes instead of learning electronic theory. Everything is ready to go except this one small but crucial piece of the puzzle.
If someone could provide me with an easy to understand schematic, it would be deeply appreciated; or even a way to modify the circuit that I have already built. I dont understand all the talk about saw tooth and ramp wave form, but I guess these are the theories that influence what I need. I already have a 556 and two 555s so a schematic that incorporated what I have would save me a week by not having to order different parts.
Please help me. Thank you.
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