momentary contact relay

[sc204]

I am new here and have a basic electronics understaning (very basic). I have an electronic device that has seperate on/off switch and start/pause switch. I would like to activate it via a timer, but you have to hit the start/pause switch after turning it on to activate it. The start/pause switch is a pcb type push button. Pushing and holding or pushing and releasing activates it. Pushing again or releasing and pushing again places the device in hold. I can easily wire to the PCB to activate the switch. Is there a cheap momentary contact relay that I could use to mimic the pushing of the switch? This I could hook up to the timer to start and stop the unit.
An internet search did not reveal anything that I could recognize as doing what I need.

Thanks for the help,
Stuart

 

[sashijoseph]

momentary relay

What you need is a monoshot built around say a 555 IC.Do a web search for 555 monoshot and see if you can build one.

 

[sc204]

momentary relay circuit

Thanks I found them. Now I just have to look at it and see if I can figure out hw to make it work for what I need. If I am thinking about this correctly my timer will activate a relay that will close pin 2 to ground and activate the 555. Output is pin 3. I can adjust how long it is active and only need the equivelent of a button push although longer is not an issue. I am not sure how this closes my switch contacts. Does this activate a second relay to close my switch? Or can I wire pin 3 output directly to the switch ?

When the timer goes off and the relay deactivates I need to have the circuit work again to place the controlled unit on pause. I guess I would need a SPDT relay to reactivate the circuit when the power is cut to the relay.
Am I making any sense?
Thanks,
Stuart

 

[sashijoseph]

timer momentary close

Does this activate a second relay to close my switch? Or can I wire pin 3 output directly to the switch ?

In all probability you'll need to use a 2nd relay,cause we don't know what the switch connects to in the device circuitry.

When the timer goes off and the relay deactivates I need to have the circuit work again to place the controlled unit on pause. I guess I would need a SPDT relay to reactivate the circuit when the power is cut to the relay.

So you need 2 pulses separated by a time event;the 1st one at the start of the timer and the 2nd one when the timer stops,right?
I've attached a (crude) diagram.Have a look.There are 2 schemes;one which employs a dual monoshot(you may use a 556) and another which tries to do it with a single 555 and a dpdt relay.
Look at the 2nd and 3rd circuits here for 555 monoshots.... **broken link removed**

And before jumping in plz call the senior members in the forum to ratify the circuit.

 

[sc204]

how to use a pause button in relay diagram

Thanks I ended up doing something similar with a single relay and and an electronic timer with multiple on/off programing to mimic pushing the button and releasing several times to reset and start and stop the unit.
Thanks for your help.
Stuart