How this soft starter work?

[pftrvlr]

Got this soft starter board from eBay. It says works for 150v - 240v, I took the chance that it may work for 120v, unfortunately it is not. Under 120v the voltage applied to the 12v relay is only 5v so it never turned on. I figure I might be able to make it work by changing some of the components. However after study the board for some time I still can't understand it. There is a 1n5360 diode, but it is 25v Zener. Anyone has any experience with this kind of soft starter?

Thanks

 

[patrick101]

It is very close to this circuit.

R1 and C1 and D1 together to make the supply voltage form the AC input. The D2 and C2 for the relay tun on delay time of the soft start circuit.

You need to change C1 to different value to get a higher supply voltage.

 

[pftrvlr]

Great! The C1 is very puzzling to me when I traced the circuit.

Thanks!!!

 

[patrick101]

no problem

 

[nigelwright7557]

Great! The C1 is very puzzling to me when I traced the circuit.

Thanks!!!

Its a capacitive mains dropper. Capacitors are good as they dont dissipate energy and so dont get hot.

 

[Mooly]

Please remember that the capacitor is a critical safety component and should be appropriately rated and also the low voltage circuitry will be 'live' at all times as there is no isolation from the mains supply.

 

[jan.didden]

Double C1 for 120V operation, but make sure to follow the required safety requirements!

Jan

 

[Kay Pirinha]

Chose a class X2 drop capacitor!
Best regards!