Help with building a Timed Relay

[aurbani]

Hi All,

Been working on this for the last 4 weeks and got no where

I am attempting to build a Timed Relay cut off.

So story behind this.

My work van has a continuous 12V power though its cigarette jacks

not good if you forget to unplug something and kill the battery (already done twice)

so what i want to do is build a Circuit that switches off after 15mins of the car been off

Now i have a trigger in place for this so need this circuit to start a time once the trigger is lost

and if i turn back on in within the 15 min the timer holds until loss of trigger again and restarts the 15 minutes again

now i have got a nice cheap circuit from china that does the job but one big issue

The trigger is a once off so once triggered the circuit starts the timer no matter if the trigger is always there it times and shuts off grrr

so every time the circuit turns off i have to restart the trigger

find circuit below

https://www.ebay.com.au/itm/DC-12V-30A-1S-1H-Trigger-Delay-Turn-On-Off-Timer-Control-Relay-Switch-Module/192178341085?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

now i have attempted to program up an Arduino with not much luck have kinda got it working then does not work so i am running out of ideas

Any help would be nice

Thanks

Anthony

[TomS_]

Not sure exactly how much this will help, as its for a slightly different purpose, but Ive just finished* building a relay timer to connect a battery to a solar charger during daylight hours.

Perhaps you can find a way to bastardise this to work to your scenario (warning, its written in 8 bit PIC assembly):

https://github.com/tomstorey/relay_timer

* Actually still a little bit of a work in progress, adding a second relay for some sequencing, and will refactor the code a bit as well

[John B]

The arduino solution would be fine.

The trigger would be something like ECU power, or any other circuit that is energised when the key is in the on position. The arduino would be powered constantly. When the trigger goes high, the relay is on to provide 12V accessory power, and when the trigger goes low, the arduino starts a 15min timer which holds the relay on until the timer reaches zero. A high to low transition should reset the timer.

[John B]

There was a recent thread about microcontrollers in automotive environments. When I use arduinos in a car, I protect the both the power supply and the digital/analogue inputs and outputs from high transient voltages.

[Gregg]

There are a bunch of timer modules available on fleabay, ali-express etc.  Search for multifunction relay module similar to this: https://www.ebay.com/itm/271958222133 (about $5)
Find one that works for you and use it in conjunction with a high amperage automotive relay along with the appropriate fuses