2 inputs 1 output

Thread Starter

Mivors

Joined Jan 20, 2021
3
Hey guys,

Im wondering if someone can point me in the right direction for what type relay is best for what I need.

I’m needing a 24vdc relay that has 2 inputs and 1 output. When input 1 is triggered then the output would close circuit. When input 2 is triggered then the output would open circuit again. If input one is triggered 10 or 20 times in a row then the output will stay closed, it will not reopen until input 2 is triggered and will not close again until input 1 is triggered. I’m hoping to use a basic user friendly programmable relay.

thanks.
 

Marley

Joined Apr 4, 2016
411
This is a set/reset circuit. In logic it's called an RS latch.
The same function can be done with relays using a "holding" contact. Remove power to reset. Commonly used in motor starters with "Start" and "Stop" buttons.
Less common are special relays called "latching" relays with two coils: Energise coil A to set the relay, energise coil B to reset tye relay. The relay usually holds using a permanent magnet internally.
 

SamR

Joined Mar 19, 2019
3,391
same function can be done with relays using a "holding" contact. Remove power to reset. Commonly used in motor starters with "Start" and "Stop" buttons.
Which requires a N.O. momentary pushbutton to start and a N.C. pushbutton to stop. Finding small N.C. tactile switches or small pushbuttons may be a problem. Far less common than the normally open ones. Same for latching signal relays for low voltage. But they can be found.
 

vu2nan

Joined Sep 11, 2014
169
You have two options.

Option 1 - Use a standard electromagnetic relay.

Momentary push button switches S1 and S2 are inputs 1 and 2 respectively.

Momentary actuation of S1 turns relay K1 on while momentary actuation of S2 turns it off.

Relay contact K1 is the output which lights the lamp H1.

The relay also goes off and stays off after power off.

1.JPG


Option 2 - Use a magnetic latch relay.

Momentary actuation of S1 sets relay K1 till it is reset by the momentary actuation of S2.

The relay status is maintained even after power off.

2.JPG

- Nandu.
 
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Thread Starter

Mivors

Joined Jan 20, 2021
3
This is a set/reset circuit. In logic it's called an RS latch.
The same function can be done with relays using a "holding" contact. Remove power to reset. Commonly used in motor starters with "Start" and "Stop" buttons.
Less common are special relays called "latching" relays with two coils: Energise coil A to set the relay, energise coil B to reset tye relay. The relay usually holds using a permanent magnet internally.
Hi,
Thanks for your reply.
I forgot to mention that the triggers to the inputs are momentary trigger not latch’s. So one momentary trigger on input 1 latchesthe output and will only unlatch when momentary trigger is recieved from input 2
 

MrSalts

Joined Apr 2, 2020
273
A dual coil latching relay does exactly what you want. Pulse the set coil with your push button #1 and press button as many times as you like and it still stays set. Then hit button #2 to briefly energize coil 2 to release it.

Done.

If you have a tiny button, you may need a transistor "switch" for each button but since you haven't shared any info about voltage, current of your switched load - I can't pick out a relay for you or whether your unspecified buttons can be used without transistor switches.
 

Thread Starter

Mivors

Joined Jan 20, 2021
3
A dual coil latching relay does exactly what you want. Pulse the set coil with your push button #1 and press button as many times as you like and it still stays set. Then hit button #2 to briefly energize coil 2 to release it.

Done.

If you have a tiny button, you may need a transistor "switch" for each button but since you haven't shared any info about voltage, current of your switched load - I can't pick out a relay for you or whether your unspecified buttons can be used without transistor switches.
Thanks for your response.
The plan was to use 24v dc relay as my trigger one to energise the coil is a negative from a 24vdc powered photoelectric sensor and trigger 2 is the same
 

vu2nan

Joined Sep 11, 2014
169
Thanks for your response.
The plan was to use 24v dc relay as my trigger one to energise the coil is a negative from a 24vdc powered photoelectric sensor and trigger 2 is the same
It's probable that the photoelectric sensors have an NPN open collector output. They are to be wired as shown.

1.JPG

Freewheeling diodes are not shown.

The coil current of the chosen magnetic latch relay should be less than the sensor sinking current. The set/reset pulse width expected by the latch relay should also be less than the sensor output pulse width.

- Nandu.
 
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