Thread: 30 Second Off-Delay timer?

Originally Posted by galvitron

Hello all,

I've searched around but couldn't find an appropriate device.

I need an off-delay timer (around 30 seconds). I am not too good with soldering so I want an off-the-shelf circuit or module that will simply delay off for 30 seconds. When the it turns ON there should be no delay, but only when turning off. This will be wired into the ignition line so it would need to be 12V.

Any ideas??

An idea ..

It's not an off-the-shelf answer, but look around for wiring diagrams on the "Retained Accessory Control" ciruits for some newer cars. This is a curcuit that keeps the accessories on, even though you have turned off the car. Then, they shut off accessories once the door (or some other trigger) is opened.

I have this on my 07 Grand Cherokee, but don't have the details on how its wired. I know i've seen it online somewhere.

I appreciate your feedback but I will need the shut-off controlled by a timer and not another trigger, like the door opening.

I did find this:

http://www.astron.nl/~smirnov/poweroff.html

But I have no idea how to calculate the right components needed to get 30 seconds. If anyone has the ability to construct this I would be willing to pay for it.

This circuit will work just fine. Istead of the 5 MOhm resistor you can use a 1MOhm TrimPot so you can adjust the time from 0 to 1 min.

Thanks MGD. Can you or anyone else recommend a place to buy this stuff? I have never bought these electronic components before...

Originally Posted by galvitron

Thanks MGD. Can you or anyone else recommend a place to buy this stuff? I have never bought these electronic components before...

I have a preference for ordering items from Mouser, and they have had a 100% success ratio with the several orders I've made (and one order had over 1000 individual items!). There's also digikey, though I have no experience with them. Be prepared to spend some time in their online catalogue finding the exact part you want, though, unless you have part numbers in advance. And be sure to have a PDF viewer installed to look at the linked data sheets =).

Locally, there's always RadioShack and (if you have one) Fry's. They will cost more then online vendors, and will a more limited selection then Mouser/Digikey -- but if they have everything you want, it might be easier in the longrun.

how about something like this is called a DEI 528t timer
http://cgi.ebay.com/DEI-528T-DEI528T...QQcmdZViewItem

How can I make that on off-delay timer? It looks like it starts the timer when trigger is started, not when trigger is lost...

this might make it easier

or this will work too, when acc is on the relay will close and nothing will happen because 87 is not connected to anything, but when you shutoff the key the relay will open and 87a will receive negative which it will send to the 528t and start the timer.