Hi all, I'm just starting to prepare a design for a relay/contactor coil driver which has a reduced power hold state - to save energy loss in a solar powered application. I don't want to use a latching relay due to failsafe reasons.

I have come across some black box products, such as the coil controllers from Albright - and Kilovac has a good read on their economiser http://www.penninecomponents.co.uk/News/PDFS/Kilovac_Data/economizer_presentation.pdf

Has anyone attempted to put together a relatively simple driver based on say a 556 and a buck converter. The initial pull in would be a few seconds with the FET on, followed by a level of pwm duty cycle sufficient for acceptable hold in - and possibly an auxiliary contact to reset the timing. The coil would typically be a standard continuous duty coil. Or maybe I need to get a little more exotic.

Ciao, Tim

 

Deleted because information was not revelant on second thought.....guess I'm getting to old for these forums

 

A simple power reducing method is to use a resistor in series with coil to provide proper hold & parall R with a capacitor to provide inrush current to initially pull in relay.

 

Thanks for the sermon, kangyuta, but what does it have to do with relays?

 

Typically this is called an "economizer" circuit. Googling that term will yield a bunch of circuits to accomplish the task.

 

Google "PWM relay driver" for lots of results.

 

Thanks guys,

I am going to be using LP339 ic's elesewhere on the pcb, so have just gone through the circuit shown in Kilovac's paper for the CCC and have calculated the component values - not too difficult. I will use a FET instead of darlington, and don't need the rapid turn-off circuit, which simplifies things a bit. Itshould all be quite neat and tidy.

Ciao, Tim