Single Shot (Rising or Falling edge) Relay

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fifty60

Senior Member
Location
USA
I am trying to find an electromechanical relay that has its set and reset function activated from the rising (or falling) edge of a 24VDC signal.

I am able to find a lot of single-shot time delay relays, and monostable multivabrator integrated circuits, but what I want is a single relay that can change states when it receives a 24VDC pulse, and then changes states again after receives the same signal again..
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150401-1421 EDT

A GE RR relay plus another standard relay will do this if the pulses are spaced by x milliseconds.

At one time P & B made a mechanical latching relay. This can do what you want.

A stepping relay is another method.

Use a divide by 2 flip-flop to drive a standard relay.

.
 

mgookin

Senior Member
Location
Fort Myers, FL
I am trying to find an electromechanical relay that has its set and reset function activated from the rising (or falling) edge of a 24VDC signal.

I am able to find a lot of single-shot time delay relays, and monostable multivabrator integrated circuits, but what I want is a single relay that can change states when it receives a 24VDC pulse, and then changes states again after receives the same signal again..

Will a latching relay do the job?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150401-1551 EDT

See http://www.farnell.com/datasheets/1470333.pdf for a magnetically latched relay. Comes in a single coil or two coil type. Fundamentally requires DC coil excitation and might require an electrolytic capacitor across each coil in the two coil device to provide sufficient energy to fully transfer the relay from one state to another. I have not worked with this relay to have experience in making it a divide by two. In a single coil unit a non-polar capacitor would be required.

.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Why electromechanical instead of electronic? There are dozens of suppliers of electronic based one-shot relays, or electronic multifunction timers with a one-shot function included. I'm not sure how you would accomplish that with a purely electromechanical device without it being a latching relay, which will have Latch and Unlatch coils, or what was called a "toggle" relay, like an alternator relay, which are not leading edge, they are trailing edge.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150401-2036 EDT

Jraef:

I don't believe he is looking for a timer, but maybe that is not clear. My interpretation is that fifty60 wants a device that changes its output state from 0 to 1 on a pulse, and from 1 to 0 on the following pulse. Any arbitrary time may exist from one pulse to the next.

To make the divide by two circuit work a SPDT contact on the latching relay is used to route the pulse to the set or reset coil ( has to be phased correctly ). A short time timer is used to generate the pulse from either the positive or negative slope (design decision). Probably better to have the latching relay control another relay that has the SPDT contact so as to add some time delay so the trigger pulse duration is not as critical.


fifty60:

Go to Magnecraft and search for stepping relays. For example: 311.

The manufacture information on relays is quite unsatisfactory. On special relays there is little information on how they work. Magnecraft does provide some description below the relays, but there is no good spec sheet.

The 311 essentially has slope detection, is a single coil, and the coil can be continuously nergized.

.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Huh, I don't know why, but I somehow missed the point in the OP... brain fart I guess.

An Alternator Relay does this. Yes, it's usually used with a Form C contact to energize two different circuits, but there is no reason why you have to use it that way. Every time you pulse the coil of an alternator relay, the contact state changes. That's what you want, right?
View attachment 12281
View attachment 12282
This diagram shows Load A and Load B, but you don't have to have anything connected to Load B.
So every time you pulse the "B1" contact, Load A turns on, pulse it again and it turns off.
 
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