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looking for some help on how to accomplish this.

What I have is a 3 way switch (off, on (position 1), on (position 2)) powered by a 12v to 13.5v DC power source (think car battery). Position 1 only needs to be used for 7-10 seconds before moving it to position 2 and I'm trying to wire an LED light to the casing of the switch that will turn on after 7-10 seconds to indicate it's safe to move to position 2.

I've been looking for a kit or some pre-built solution and everything I'm finding that uses the 555 timer or just a cap that drains in the desired timeframe seem to trigger off a momentary switch. Since this would be powered off the same terminal as position 1 of the switch this means it'd have constant voltage until moved to position 2 or off and I'd prefer to not to also have to push a separate button to enable the timed LED.

Here's one kit I was looking at: https://vakits.com/lm555-timer-one-shot-kit-1-11701

Is there a kit or pre-built solution out there that can accomplish this, or, a modification I could do to the above kit to accomplish it?

toolic
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PHRoGeDD
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  • What voltages are we talking? And is it DC? If DC and e.g. 12V there can be simple solutions. If not: then not. – ElectronicsStudent May 03 '23 at 07:02
  • Sorry, 12V DC from a car battery. – PHRoGeDD May 03 '23 at 07:07
  • "12v to 13.5v DC power source (think car battery)" When the engine is running, a car battery can range up to 14.7V. – Velvet May 03 '23 at 07:27
  • No engine involved here. – PHRoGeDD May 03 '23 at 07:29
  • This page seems to be what you want. You could certainly buy a module and then modify it to do this. Alternatively you can get delay relays that do the same thing. – Finbarr May 03 '23 at 07:33
  • @finbarr Yes!! That's exactly what I'd like to do...ideally, I'd like it to be as small and consistent as possible. If a simple relay would do it, that'd be ideal...able to point me in the right direction as to what relay I'd need or a kit that'd work? (adjustable would be neat). – PHRoGeDD May 03 '23 at 07:46
  • "As consistent as possible" isn't a realistic specification, for that you'd need a temperature compensated crystal oscillator driving a small microcontroller or a bunch of logic. Something like this module ought to be more than good enough for a pretty non-demanding application like this. – Finbarr May 03 '23 at 07:54
  • @finbarr apologies, consistent wasn't the best word choice there. This won't be turned on/off often at all.

    Position 1 on the switch simply pre-charges capacitors in an inverter before powering on the system. The battery is li-ion and has a low IR that can damage the switch contacts if the inverter capacitors are drained.

    I've seen the module you linked and I'd prefer something smaller if possible, since the installation space is limited. Looks like I could do first page you linked without a PCB (one would be nice tho) and simply add a discharge resistor to ensure the cap drains.

     – PHRoGeDD May 03 '23 at 08:27
  • I wouldn't bother with a three position switch - just on/off with a timed delay to power the system. Simpler to use and less chance of getting it wrong. – Finbarr May 03 '23 at 08:47
  • @Finbarr I did consider that at first...planned on using on/off with a timed relay (like you posted) to trigger a much larger relay (capable of 500A) to power the system. However, the large relay would consume too many watts for my liking to keep the contacts closed while powering the system as I'm trying to maximize the amount of battery life available. The 3 position switch allows me to use the 1st to pre-charge the inverter and the 2nd to power the system without any additional power consumption. – PHRoGeDD May 03 '23 at 10:59
  • Then choose a relay that's suitable for the current you need. What is the inverter rating? – Finbarr May 03 '23 at 12:05
  • @finbarr It's 4kW. – PHRoGeDD May 03 '23 at 12:22

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