For most application driving the solenoid valve we just apply the proper voltage to the coil. But we found the coil became very hot for continuous driving for a while.Here I had a solution to reduce the power consumption when it driving It worked like this,when the power DC24v apply it and the capacitor charging for large current and the coil same get the current and the valve activate, capacitor charging for a while the charging current reduced and the voltage across the coil devide by the resistor low down the power of the coil and the coil get only a little heat.
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First step you should test the solenoid valve "holding"voltage and "inrush" voltage. Connect the solenoid valve and adjust the voltage from 0v to 24v and you should hear the activated noise "ka". For this example it about 20v, it means the voltage must be large than 20v the valve activate.(This we call holding voltage). And then turn the voltage from 24v to 0v, same as before you can hear another "ka" noise, it means de-activate (or released). For this example it about 3v.(This we call inrush voltage)
Second step we measure the coil resistance use the multimeter. For this example it about 66 ohms at coil resistance.
Decide the ceramic resistor, There is a voltage devider of coil and ceramic resistor. So we choice the 220 ohm resister and make the voltage across the coil about 5.5v large than 3v , It means the valve always activate at 5.5v(because it large than 3v), but the coil consumption less power (less heat).
Attention: this method only for DC driving valve, (for AC driving valve it maybe use TRIAC or SCR structure)