Hi
I have a 12 volt relay being activated by a timing circuit (so 12 volts is on the relay while it counts down the prescribed time)
I need a trigger pulse or switch pulse when the relay is energised and one when the relay is De energised
Thanks Shane

 

What is the nature of the system that is required to monitor the relay?
Max.

 

Hi
just need 12v trigger to activate a 2.5v-12v input
The input (IN) requires just a few milliamps at anywhere between 2.5v and 12v.
Thanks

 

Since you do not mention any timing periods this will be generic. I would think about using a pair of One Shot multivibrators. Something along the lines of a 74123 simply because it is dual and allows for + or - triggering. Again, you do not mention the pulse width once triggered?

Ron

 

Hi
the trigger has to run a relay pcb with the following specs (The input (IN) requires just a few milliamps at anywhere between 2.5v and 12v)

 

You want a pulse when a relay coil is energized and you want a pulse when the coil is de energized. Call these pulses triggers or whatever you want but they need a pulse width or duration? So when 12 V is applied to the coil you want that positive transition to create a pulse and when the 12 V is removed you want to create a pulse on that negative going transitional edge. Use a pair of one-shot multivibtators. The 2.5 to 12 V isn't the issue. Additionally DC coil relays usually have a diode across the coil to snub the inductive kick when the coil field collapses, that may need some consideration. Commonly called a "flyback" diode.

Ron

 

You want to use the relay contacts to generate the pulses, or do you want to use the voltage across the relay's coil?

 

Hi
I was going to try and use the relay contacts

 

Hi
I was going to try and use the relay contacts

Do you have form C (NO,NC) contacts?

So you need two outputs; 1 positive going when the relay closes, the other a positive going pulse when the relay releases?

 

Yes the relay has C, NO, NC Contacts

 

Yes the relay has C, NO, NC Contacts

So you need two outputs; 1 positive going when the relay closes, the other a positive going pulse when the relay releases?

 

yes this is correct

 

I made some assumptions:
You have 12Vdc available.
Each input of the relay board looks like a resistance of ~2kΩ.

 

Thank you MikeML for your help I will build the circuit and give it a go
Thanks Again for you help