auto lock car door after ignition off

greetings. as a new poster, if this is not the correct way/place to ask for help, please let me know.

have a 2011 prius and want a feature of the alarm on my old car back. 20 sec after i turn off ignition and shut all doors, the doors lock . i am good at building electronics, but don't know enough about the various circuit types available to design them. what i think i need is this: a 555 timer circuit to give single pulse after a delay to activate door locks. i don't know how to trigger it.

planned trigger will be ignition off AND door closed- ignition state determined from cig lighter, door from ajar indicator so only both being absent triggers start of 20 sec countdown, and return of either (reopening door) resets to 20 sec (but doesn't cancel countdown).

the 555 circuit (such as a two stage time delay circuit, ?with a reversed trigger input?) seems to do what i need as far as the delay and pulse, what i don't know enough about is the trigger. i don't know if that needs to be a pulse or if simply being +12v or not will work. also, having the timer restart if the door is reopened is something i can't get for sure- some descriptions say reapplying the trigger before the timer counts down will reset it, other say it doesn't affect the countdown and i'm assuming it's related to how it is wired up.

honestly, i won't grasp this quickly enough to avoid spending hours trying to design, only to build and see it fail due to something i didn't realize would happen. so, i sought to ask help from those with much more experience than i. i hope this forum is for this.

thanks very much. everette

So the one time you get out of the car leave the keys in the ignition and shut the door, it's hello AAA, except you can't 'cause your cellphone is in the bloody car. This can be done with two mini relays in series, from an ignition source and the dome light but I'm not going to tell you, it's too dangerous.

It would be nice to add a "warning" beep. Say after 20 seconds the system beeps once quickly and then 10 seconds later it locks the doors. This would at least give you a chance if for some reason you left your keys in the car (filling up or whatever). My Dad LOVES passive arming. I, myself, hate it. He has been using passive arming for 10+ years and I don't believe he has ever locked his keys in his car (yet). This would be a simple task for a programmable microcontroller and some basic hardware. I could put something together, test it, and send it to you (for the cost of materials and shipping). Shouldn't be too much ($25 or so shipped UPS?) and shouldn't take too long.Kevin Pierson

that sounds great, and reasonable. thanks Kevin.

i have used the auto lock after 20 sec (no warning beep) for 10 yrs and, like your father, have never locked my keys in the car, nor will i ever. i appreciate your helpful answer..... others- the prius has no key.

let me know how it's goin'.

everette

Cool, I'll try to work on it today. I'll post pics of my progress.Kevin Pierson

Well, I think I pretty much got it all done today! Here is the board with all the components in it (before soldering): Bottom of board (before soldering): Board completely soldered, microcontroller installed, wire harness (with 3A inline fuse) attached: Completed module ready for shipping: I went a little extreme with it. The processor looks for the (+) ignition to be turned on, then waits for it to go back off. It then looks at the (-) door pin input and waits for the door to open then close again. At that point, there is an LED output that starts flashing slowly for 20 seconds. During this 20 second period the processor is monitoring both the ignition input and the door pin input - if either of them toggle their state the timer pauses, then starts over once both signals are clear. After 20 seconds the module outputs a short beep through an external hood mounted beeper and then the LED starts flashing quickly for 10 seconds, while the processor continues to monitor the inputs (and resets to the very beginning if something changes). At the end of this 10 second period the module outputs a (-) door lock signal for ~0.8 seconds. Finally, the LED output flashes at a slow rate to simulate an aftermarket security system. The system can operate without the LED and without the beeper if they are not desired. The module is centered around a microprocessor running at 1.2mhz. It has an automotive grade power supply with reverse polarity protection. The (-) lock output has a clamping diode on the board (so no external diode is needed if using an external relay). At idle (during slow flashing stage) the entire circuit draws 0.5mA. All inputs are current limited to 1.5mA and all outputs are current limited based on their function (LED out = 15mA, Beeper out = 150mA, Door Lock out = 682mA). All Inputs and outputs go through buffer transistors for added durability. The wiring harness parts are genuine Molex components crimped on a Molex TM40 press. The wiring harness is detachable with a ramp type lock holding it together. There is a 3A inline fuse for protection. Finally, the circuit board is housed in a small 2"x2"x1" plastic enclosure for protection. What do you think?Kevin Pierson

Bloody brilliant, on my own experience your daughter will be helping you in about 7 years, joking aside nice work.

WOW, looks great. PM me and let me know how to complete the deal! there were a few persons on the prius forums who had interest in this (a few years ago), would it be OK to let them know about this? let me know in the PM.

thanks much. everette