Driving a relay that requires reverse polarity

Hello, I am looking to control a bistable relay (Hongfa part # HFE10-L/24-DT-L1) which is a relay that keeps it's position without the need of keeping the coil powered. Usually they have two coils, one for on, and one for off. In that case I could just use transistors and pulse each coil to set the position of it.

However this one, which is the one I need, has one coil. It is flipped one way by putting voltage across the coil in one direction, and flipped the other way by reversing that voltage.

My question is how I would go about controlling this. and where would I put the diode? Usually you put the diode across the coil in reverse so it has no effect when powering the coil. But in this case the coil needs to be powered in either direction. I could technically use a bunch of transistors to control the polarity but is there an IC or something that would do this for me? Also I think there is some diode that would work for this but I don't know what it is called.

If it matters here are some parameters on the relay:

  • 24Vdc coil
  • Min pulse time off 50Ms (I will use 100Ms for reliability)
  • Coil power ~1.5W

Thanks in advance!

HFE10-L_en.pdf (1.49 MB)

An h-bridge could be used to reverse polarity. Some are made for driving motors and have the diodes built in.

Is there a particular H-bridge that would work good for this? I am looking into them and it seems they are all meant for DC motors. I don't know if this would cause any issues by driving a coil directly or not, or if the hight feedback voltage of the coil is more than a motor would generate. Also it will need to be in a dip package so I can put it right onto a pcb.

"Poor Man's H-bridge" (Google it).
Leo..

You could use 2 monostable relais to build a H-bridge with normal-off to drive the relais :slight_smile:

Along with the answers above google can also be your friend.

As can the upgraded search function of the forum.

Sadly the dual coil edition of this relay is more expensive in low quantities, so I am sticking to the single coil one. I guess I could make a H bridge with transistors and just control them with digital pins. Any suggestions on the diode issue though? I don't know how to protect the transistors from the reverse voltage the relay makes.

Sorry, I seem to have posted the wrong diagram for a "Poor Man's H-bridge",
and can't find a proper diagram online.

It's just a two NPN transistors with two collector resistors and two base resistors, with diodes across the collector resistors. The relay coil connects to the two collectors.
Values depend on the relay used. In this case <=100 ohm collector resistors are needed.
A simple design like that draws about five times the relay current for a short time (in this case),
2N2222 transistors and 220ohm base resistors are required.
If that's a problem, then us a H-bridge chip.
H-bridges usually have kickback diodes build-in.
Leo..