Use of a toggle switch to do a momentary action. - Page 1
Forum section: electronics / beginners

author: Qideil
author_rank: Newbie
timestamp: March 23, 2021, 03:57:04 pm
content: I’m looking for a way to use a toggle switch (on/off) to send short impulses to two solenoids. One should be activated when switching to ‘on’ position and another one – to ‘off’ position. The solenoids require 16VAC and can draw up to 1.5A.I saw a few examples how to achieve this with push buttons and discharge capacitors, but I failed to find a way to do it with a trigger. I also thought to use a relay and capacitor, but it’s close to impossible to find a relay for 16VAC on coil and I will have to introduce another voltage just to activate the relay.I’m guessing it should be a combination of a couple of capacitors and transistors, but I don’t have enough knowledge to put it together.Any suggestions are welcome.

author: wizard69
author_rank: Super Contributor
timestamp: March 23, 2021, 04:36:04 pm
content: Quote from: Qideil on March 23, 2021, 03:57:04 pmYou are missing info here. For example what is doing the triggering? You can buy relays that operate at 5VDC and even 3.3 VDC, to operate from microprocessor circuits. As for the capacitors I'm not sure what your intentions are. Solenoids / relay coils, produce inductive spikes that need to be addresses, usually with diodes but sometimes additional suppression is used like capacitors.I'm not sure what has you on this project but you really should start at the bottom, studying basic electronics. With your description it will be hard for people to help you and even then you need to understand electronics well enough to implement anything discussed here.

author: Qideil
author_rank: Newbie
timestamp: March 23, 2021, 05:16:02 pm
content: Quote from: wizard69 on March 23, 2021, 04:36:04 pmA mechanical trigger switch, which is the essential part of the question.Quote from: wizard69 on March 23, 2021, 04:36:04 pmTo discharge and activate one of the solenoids when the switch pushed to off position, for example.The simplistic circuit could look like on the picture. It has a few flaws that I would like to avoid. First, it need DC, so I need to rectify 16VAC I have. Second, if the switch is in 'on' position during power up, the top solenoid will be activated right away, and I would like that to happen only when the trigger flipped one way or another.

author: ledtester
author_rank: Super Contributor
timestamp: March 24, 2021, 09:44:53 am
content: QuoteLook up "monostable multivibrator". They emit a pulse when an edge (can be either positive or negative) transition is detected.http://www.n5dux.com/ham/files/pdf/Working%20With%20Monostable%20Multivibrators.pdf

author: Qideil
author_rank: Newbie
timestamp: March 25, 2021, 11:04:17 am
content: Quote from: ledtester on March 24, 2021, 09:44:53 amThank you for the suggestion, but I think it requires a push (momentary) switch and I need to use a toggle (latching) switch.

author: tooki
author_rank: Super Contributor
timestamp: March 27, 2021, 01:20:45 pm
content: Quote from: Qideil on March 25, 2021, 11:04:17 amNope. They act ONLY on the edge (the transition). Look at figure 6 in the PDF linked above: it shows how the trigger pulse can exceed the length of the output pulse.In other words, the output is always a fixed-length pulse, even if the trigger is “held down” indefinitely.

author: drussell
author_rank: Super Contributor
timestamp: March 27, 2021, 02:07:15 pm
content: Quote from: Qideil on March 23, 2021, 03:57:04 pmCouldn't you also use an (ON-ON) switch (SPDT with no center-off position) instead of on/off so then you just have to time limit your pulses to the solenoids?QuoteI think people here are a bit confused by what you mean "do it with a trigger." Perhaps you could explain a little more what exactly you're trying to do, how long the "pulses" need to be, etc. do people can understand more clearly.

author: wizard69
author_rank: Super Contributor
timestamp: March 27, 2021, 02:26:45 pm
content: I'd probably approach this as a machine control problem. That means buying a micro PLC or programmable relay. The more engineering intense approach would be using a PIC or similar micro controller and build up the circuitry required to power the relays.In any case having something you can program would be the easiest way to assure you can meet your loosely spec'ed requirements. Personally I'd rather know more about what you are trying to achieve as trying to run two solenoids off one toggle switch is just odd. More info on what those solenoids are trying to do might allow for other suggestions.