Hello, I have designed this circuit to control a FOTEK SSR-40DA using an ESP32 GPIO pin. This design is intended for mass production, and I would appreciate any advice or suggestions to optimize it before proceeding. My ultimate goal is to control 4kW 220V heating element. Control means just turn ON for lets say 10hrs and then OFF for 2hrs or something.
Here are some details:
R2 is a pull-down resistor, ensuring the transistor's base is pulled to GND when the GPIO outputs 0V.
R5 is another pull-down resistor to ensure the SSR input is properly grounded when inactive.
I welcome any recommendations for improvements or validation of this approach.
For production work, R1 and R4 should be the same resistive value if the wattage are the same. Can you put the LED in series with the LED in the Fotek SSR?
D1 is unnecessary because of the optocoupler at the low voltage side. Right?
Yes, some safety should have been there. As FOTEK SSR will not be a part of the PCB I was thinking of placing Fast-Blow Fuse of lets say 12V and 500mA on pin 1 of CN7 (connector). This will protect the low voltage side if SSR burns down for some reason and live wires gets shorted with low voltage wires. Will this be a good idea for production scenario?
This circuit will be placed in extremely hot outdoor environment in metal casing. The outside open air temp will be about +55C in summers and -5C in winters. This will make the inside metal box temp even few degree higher. Considering all this should there be any changes in the circuit or some protection that should be used.
Sure! Part of the cost to build a circuit board by hand or by machine is the number of different components that must be inventoried and ensured that the proper value is placed in the proper location on the circuit board. If the resistors are identical in all respects, then it is very quick to find and place each one without taking time to ensure the right values are in the right places. Time is money and keeping inventories of two different resistors also costs money.
The costs apply to capacitors. A circuit calling for two capacitors that are identical except for temperature change ratings will be more costly than using just the one capacitor with tighter temperature tolerance in both locations.
