Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Timed Relay for Latching Loop with Momentary Push Button

Timed Relay for Latching Loop with Momentary Push Button

Timed Relay for Latching Loop with Momentary Push Button

First of all, I am a complete newbie at this. My terms and drawings are basic and cartoonish, but I want to learn and explore since it fascinates me. I have a simple setup where I use a 12v battery to supply power to a multi switch relay that then does several other things (not relevant here). I use a momentary button switch.

The problem was, I didn't want to keep holding the button for continued current and I didn't want to use a toggle switch because I didn't want to forget to turn it off. So, I just ran a loop from the two terminals of the momentary button switch to latch it. Now, the main relay had continuous current, even when I released the momentary button switch.

You guessed the next problem I had, now I had to cut the power from its source to release the current from the main relay to reset it. So my question is, can I place one of these really cool delay timer switches on that latching loop so after the timer expires it will sever the latch current and reset the main relay until the momentary button is pressed again?

What I was thinking is running the loop to the VCC on the NE555 switch (red) and then back through the CB (blue). I would then run the ground back to the battery (green) and set the relay to 10 seconds, so after that time expires, the loop will be severed and both the main relay AND this timer relay is reset until the push button is pressed again.

What do you think? Will it work?

RE: Timed Relay for Latching Loop with Momentary Push Button

Google: 555 monostable

edit: to see how to wire it up, if you're using a premade circuit.

Or try your hand at programming an Arduino or similar.

RE: Timed Relay for Latching Loop with Momentary Push Button


Not sure I'm following, even with your snazzy pictorial. I completely get what you're after but I'm not sure how you're getting it with this.

You normally use a double pole relay to "latch" the circuit. One pole is wired directly across the push-button shorting it so it acts like it's continuously pressed once the relay is engaged.

The other pole of the relay runs whatever you need running.

To drop out the circuit you'd have a normally closed button wired in the circuit anywhere to interrupt the power because as soon as it's interrupted the latched relay drops out 'unpushing' the button.

In your case the time delayed circuit needs to interrupt the latched part of the circuit. Once you have this timer component involved it usually makes more sense to just use it for the entire task.

What you seek is called, in the industry, an "off delay relay". Which means as soon as the relay is triggered or energized its output goes ON. Then a settable delay later the output goes OFF; hence the "OFF DELAY".

google or better yet duckduckgo.com "12v off delay relay" and you will see scads of them for 10 bucks.

Keith Cress
kcress - http://www.flaminsystems.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close