Just Enough to Be Dangerous

As the title emplies, I know just enough about this... but was hoping to get some backup before I place some current to this project.

Here's the background for the project:

An AC drive unit

formatting link
is being controlled by a radio remote.

The drive has both fwd and rev functions that have to remain latched to operate. I'm wanting to setup two functions on the transmitter of the remote: one fwd, one for rev. But one function needs to be turned off, when the other one is operating, and visa versa.

I'm thinking a simple, single coil latching relay will accomplish this, but I've never worked with one so here is where I'm in need of some help.

Looking at the wire diagram of this relay

formatting link
should there be a constant 12vdc current on the coil, and the switches operated with simple open and closed "dry" circuits? (if 9 and 6 are closed, 7 and 4 will close?).

More background, the remote signal can either be momentary or latching.



Reply to
Clyde Gill
Loading thread data ...

One way would be to use a polarized relay that stays on whichever side it was last driven to. The coil needs a positive or a negative DC pulse to switch it over and then it will remain ther until it receives the opposite pulse.

If you can send two different momentary radio frequencies for "forward" or "reverse", they can be decoded simply as a positive or negative DC pulse to the polarized relay.

Reply to

was hoping



transmitter of

be turned


need of

the switches

and 6 are


a latching relay only takes momentary power to close and latch in that position... then depending on the relay, a second momentary powering unlatches the relay and it opens.

Thus the term latching relay

non latching relays require constant power to operate the contacts.

Phil Scott

Reply to
Phil Scott

Just out of curiosity, why don't you build a forward/reverse starter circuit and keep it all AC? You could even use a 4th contact as the maintaining contact for each circuit on each relay.

L8TR, Mod

Reply to

First; responses to my original question are greatly appreciated. I've been rushing around trying to finish up this year's harvest and have not had the time to properly acknowledge the help.

The first two responses clued me in on how a relay like this would work. A momentary dc voltage applied to the coil(s) will switch circuits like I wanted (open one, while closing the other and visa versa). Using a dual coil allowed me to use a separate switch to reset the circuits to their original state.

Mod, I'm not following your suggestion... the controls I'm dealing with seem to be 'happy' with a dc system, which was also readily available as an output from the ac drive. Is there an advantage to using ac over dc for controlling relays?

One more question, if I may. I've got the unit functioning as intended... here's the wiring diagram:

formatting link
plus the layout of the relay:

formatting link
My concern is with switching on the common side of the system (a- and

5-). Like I said, it's working, but is there any problem with continuous hot leads to the relay (B+ and 8+). Originally I was switching the positive side, but I had separate common terminals on the receiver. That option is not available on this new, better receiver.

Any other problems with this layout that a relative novice like me might be missing?

Also, a question about torque settings on an ac drive:

Is it posssible to have the torque boost setting too high? Can it cause damage to the motor?

Bumping up this setting was necessary to have the motor start with decreased acceleration setting. My particular pump has trouble reversing due to the substantial amount of resistance, and I'm curious if higher torque boost could do the trick... without burning up something. Any references where I can bone up on torque applications?

thanx again for previous and future help,


Reply to
Clyde Gill

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.