# Voltage for relay

I wanted to ask that is it good to giving 12v to 12v operated relay from 230v to 12v transformer+ rectifier + 1000uf 50 v capacitor , I am taking 12 v and ground from capacitors legs !

• Carefully measure the actual voltage across the capacitor with a multimeter (in DC voltage mode). You will almost certainly find it higher (perhaps much higher) than 12V, and therefore perhaps exceeding the maximum coil voltage for whatever relay you are using - check its datasheet for that maximum value. Mar 10, 2016 at 17:03
• How much current does the relay coil take? Or better, yet, can you edit your question and add a data sheet or at leas a link? Mar 10, 2016 at 17:20
• @SamGibson. The rectified voltage across the cap will rise to 1.414 times the transformer's RMS output voltage and decay at a rate depending on the capacitance, the load current, and the period of the charging waveform . Mar 10, 2016 at 17:35
• @EMFields - agreed, I know I could have mentioned sqrt 2 etc. Due to the lack of specific data from the OP, I thought a quick way to answer his stated question (i.e. is [that setup] good) was to measure the voltage, assuming that the OP was already using this circuit (I now see its ambiguous whether this is a theoretical question or already in use, as I interpreted it). The unknown load on the output, relative to the unknown transformer rating, means we don't know what the actual transformer output voltage will be (do we?) - hence measure it :-) Yours is a more complete approach :-) Mar 10, 2016 at 18:29
• Please provide a schematic and clarify your question. Mar 10, 2016 at 18:46