DC Impedance relay

[Severus_king]

I am currently using a solenoid as a switch for an application. However, when it`s on the solenoid keeps draining the batteries. I was thinking of using a current relay to turn the solenoid off when there`s no load and turn it back on when a load appears across the solenoid terminals. My idea was to determine the impedance across the solenoid terminals to see whether a load has been turned on. Can anybody please suggest a DC impedance measurement method to implement this? Or is there a simpler way that I am overlooking?

Thanks

 

[gar]

100729-1601 EST

Severus_king:

I do not know how the moderators view your question so they may close this.

One possible way to solve your problem is to employ a mechanically bi-stable relay. A GE RR7 would be an example. A pulse of energy to one coil sets the relay to the ON state and a pulse to the other coil sets it to OFF. So energy is only consumed when changing state.

Another way this can be achieved is with a single coil and a polarity to define which state is set.

.