Help with building a Timed Relay - Page 1
Forum section: electronics / projects

author: aurbani
author_rank: Newbie
timestamp: February 04, 2020, 06:35:53 am
content: Hi All,Been working on this for the last 4 weeks and got no whereI am attempting to build a Timed Relay cut off.So story behind this.My work van has a continuous 12V power though its cigarette jacksnot 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 offNow i have a trigger in place for this so need this circuit to start a time once the trigger is lostand if i turn back on in within the 15 min the timer holds until loss of trigger again and restarts the 15 minutes againnow i have got a nice cheap circuit from china that does the job but one big issueThe 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 grrrso every time the circuit turns off i have to restart the triggerfind circuit belowhttps://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.l2649now 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 ideasAny help would be niceThanksAnthony

author: TomS_
author_rank: Frequent Contributor
timestamp: February 04, 2020, 08:55:44 pm
content: 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

author: John B
author_rank: Frequent Contributor
timestamp: February 04, 2020, 10:08:59 pm
content: 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.

author: John B
author_rank: Frequent Contributor
timestamp: February 04, 2020, 10:14:32 pm
content: 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.

author: Gregg
author_rank: Super Contributor
timestamp: February 05, 2020, 03:06:50 am
content: 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