prevention for Momentary on switch being held - Page 1
Forum section: electronics / beginners

author: Maquera
author_rank: Newbie
timestamp: September 21, 2023, 09:32:59 pm
content: Hi All, First time posting so I am hopeful that I have a community that will help a Noob. I am having an issue with a momentary on push-button switch being held in due to ingress which causes the circuit to send constant power to an actuator which allows it to overheat and burn. Assuming we need the Push-button activation for this actuator and that the ingress is almost guaranteed, what method would you suggest to cut the power after 10s of the switch being held in? We've attempted to use multiple fuses, however they either cut out too soon (1s after the actuator is toggled) or too late (after the actuator is smoking. The solution needs to be as simple as possible. As further information, the circuit runs on 13v and current draw is up to 7a.

author: John B
author_rank: Frequent Contributor
timestamp: September 21, 2023, 11:28:25 pm
content: The switch is passing 7A? This sounds like a job for the 555 timer in a monostable configuration controlling a large power mosfet. You'd probably want a voltage regulator and input protection to protect the 555, and then pot the whole lot to seal it against water.

author: Kim Christensen
author_rank: Super Contributor
timestamp: September 21, 2023, 11:31:38 pm
content: You could put a timer relay between the button which disconnects the load X seconds after the button is pushed.Are you looking for something industrial/premade or DIY?

author: Maquera
author_rank: Newbie
timestamp: September 22, 2023, 01:00:39 am
content: Hi John and Kim, an off-the-shelf solution would be best as myself and the people I work with are completely illiterate when it comes to electronics and basically know how switches work. The Timer relay would be an awesome Idea, is there anything that you would possibly propose as a solution?

author: wraper
author_rank: Unknown
timestamp: September 22, 2023, 01:24:38 am
content: Quote from: Maquera on September 22, 2023, 01:00:39 amBuy a DIN rail Timer Relay (Time Delay Relay) and contactor if more load capability is needed.

author: themadhippy
author_rank: Super Contributor
timestamp: September 22, 2023, 02:12:27 am
content: stick a drawing pin to to the switch ,that'll stop the buggers holding the button in for too long.

author: ledtester
author_rank: Super Contributor
timestamp: September 22, 2023, 04:17:54 am
content: Quote from: Maquera on September 21, 2023, 09:32:59 pmI have a question about how you want the switch to operate...When the user presses the switch do you want:A. power to be sent to the actuator for exactly 10 seconds regardless of how long the user continues to press the switch, orB. power to be sent for only as long as the switch is pressed but not longer than 10 seconds.i.e., what should happen if the button is pressed for only 3 seconds?And is it a person holding down the switch?

author: eblc1388
author_rank: Frequent Contributor
timestamp: September 24, 2023, 01:28:13 am
content: Unless the switch is being held down by a person, then the above suggestions would work.Else choose a proper switch, optimise its mounting location/position and prevent ingress by the use of full or partial shielding/covering.

author: pickle9000
author_rank: Super Contributor
timestamp: September 24, 2023, 03:52:40 am
content: try an "off delay relay"

author: EPAIII
author_rank: Super Contributor
timestamp: September 24, 2023, 07:13:26 am
content: He used the word "ingress", not idiots. I think that means some THING, not some person. Air, water, sand, parts, or something that bears against the switch or a part between it and the something.A relay or timer module (DIN rail mounted or otherwise) is what is needed. But the exact behavior should be carefully specified. So just how long should the power be applied? And what should happen if the switch remains pressed? What should reset the relay or timer? After how long of a rest interval?If the switch could be activated a second time briefly after the power to the actuator is released, then it may still be possible to overheat it. So a minimum rest time may be needed between activations.Quote from: themadhippy on September 22, 2023, 02:12:27 am