Need help making a relay latch - Page 1
Forum section: electronics / beginners

author: Qmavam
author_rank: Regular Contributor
timestamp: May 21, 2023, 04:20:52 pm
content: I thought this would be simple and maybe the problem is I need a DPDT relay, But I don't have one available.I have a relay that closes for 30 seconds then opens. It is a SPDT relay. I can retrigger the relay to run another 30 seconds.I want to add a second latching relay with a reset.When the 30 second runs out and the relay is set to the N.O. contacts, I want a buzzer to sound, I also want to be able to reset the latching relay to shut the Buzzer off and I want it to stay off until the next to the relay runs through a 30 second cycle and drops out to the N.O. contacts.Long story short, I have a timer, I push start and it closes the relay N.O. contacts for 30 seconds, then the relay opens and the N.C. contacts are closed. When the N.C. contacts close, I want them to latch a relay with a reset button. Reset is to shut the buzzer off, while work is performed before the next 30 second cycle is triggered.Thanks, Mikek

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 21, 2023, 05:10:12 pm
content: Go to the store and buy a $3 DPDT relay instead making it more complex?

author: Qmavam
author_rank: Regular Contributor
timestamp: May 21, 2023, 07:14:44 pm
content: Quote from: DavidAlfa on May 21, 2023, 05:10:12 pmThere is no store I can go buy a DPDT relay, It's Mail Order Only.Is it more complex more do it with a SPST, or can't it be done.I haven't figured out how to do it with a DPDT.Do you have a circuit?Mikek

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 21, 2023, 09:26:12 pm
content: Pretty generic, not knowing how the wiring goes, the voltage, the timer outputs...

author: Qmavam
author_rank: Regular Contributor
timestamp: May 21, 2023, 10:37:39 pm
content: Quote from: DavidAlfa on May 21, 2023, 09:57:27 pmI may not have explained well. Here is a picture of the timer PCB and it's relay.QuoteNot sure I understand the connected device, I thought that was the symbol with the Circle with an X inside?My timer just has a power switch.After searching I did find one 12V DPDT Relay! So I have that and a 12V SPDT relay. Any thing we can do with just those and the timer output?Thanks, Mikek

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 21, 2023, 11:52:06 pm
content: So then explain it for the beggining:- I have only ONE SPDT relay.- I have this timer.It's ok to ask for help, but wasting other's time for not explaning properly is notThis will do the same taking advantage of the timer outputs.The buzzer must also work at 12V!If you don't want to power anything by the timer signal the SPDT relay (The one with "Switch" terminals) can be omitted.Edit: Fixed accidental latching of second relay.

author: Qmavam
author_rank: Regular Contributor
timestamp: May 22, 2023, 01:14:13 am
content: Sorry, for the wrong info, I truly didn't think I had a 12V DPDT relay, I have about 30 relays, but all are SPDT or 24V, 48V, and on up, I finally found one lone 12V DPDT relay.I have it all mocked up and tested, and it works fine, I changed the reset switch on my schematic to a push to open. Which is what I think you meant it to be. Tomorrow I will get it in an enclosure and mount the switches. I'm using this count down timer, second or minutes, switchable.https://www.mpja.com/Retriggerable-Time-Delay-Relay-Delay-on-Break-12VDC/productinfo/37663+RL/Thank you for all your help, Mikek

author: Qmavam
author_rank: Regular Contributor
timestamp: May 22, 2023, 06:33:29 pm
content: I have decided to incorporate the relay on the right side (an SSR) to switch an AC load. This is the relay that I said I may or may not use.However, I see that after the 30 sec countdown the first relay is latched causing the relay on the right to stay on, after the countdown has ended, it will only release when reset is pushed. I want it off after the countdown has finished.Is there a fix for that?Thanks, Mikek

author: Qmavam
author_rank: Regular Contributor
timestamp: May 22, 2023, 07:57:20 pm
content: I was given the solution, just add a diode![ Attachment Invalid Or Does Not Exist ]

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 22, 2023, 08:15:28 pm
content: Your image is missing!Yep, I made a little mistake there! I modified the original message.