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How can I run a 12 Volt Relay in 220 Volts AC mains?

I don't want to use or have more space for a transformer and a diode bridge inside the machine I'm makingThe voltage is 220V ACThe relay I shall use is of 12volts 200ohmsCan I use a resistor of big value (like 82K from power dissipation calculations) and a diode in series with the relay (to feed halfwave rectified DC to the realy)? Will it work? Please suggestThank you.


OK Tiger, you have 2 issues here1, the relay is a 12V DC type and will need the AC changing to DC using 4 diodes in a bridge2 the relay is 12V so you need to drop the 220v down to 12V, try a series capacitor in a circuit known as a 'Wattless dropper'you will need to calculate the capacitor value using 1/Xc 1/ 2piFc ans a bit of Ohms lawThis will resolve the heat and wasted power issueMy solution would be to buy a 220v relay for less than ?5GBP from Maplin Electronics or a similar store.

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