trigger when alarm releases ground?

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mr_hyde

Member - Posts: 14

Joined: October 09, 2008

Posted: September 17, 2009 at 9:33 PM / IP Logged

I have an alarm that's only extra output is to release a ground when it is disarmed. I have some extra devices that need to get power when the alarm disarms and I can't do it with a simple SPDT in this configuration because the relay's coil would drain the battery while the system is armed. I need some help finding a device that will do this. Again - one output, ground when armed, open when disarmed and I need accessories to turn on when the unit disarms. Standard +12v automobile. Thanks for any help you can provide!

-hyde

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: September 18, 2009 at 7:45 AM / IP Logged

Use the unlock output with maybe a timed or latching relay device, what are you tring to do and what alarm is it?

91stt

Silver - Posts: 564

This member consistently provides reliable information

Joined: May 24, 2006

Location: New Jersey, United States

Posted: September 18, 2009 at 9:50 AM / IP Logged

How long does it have to be on for?

How much current does the device need?

mr_hyde

Member - Posts: 14

Joined: October 09, 2008

Posted: September 18, 2009 at 10:27 AM / IP Logged

It needs to hold the entire time the ground is missing and has to release when the ground returns so it doesn't necessarily need to 'latch'. I would think someone like DEI makes a purpose built unit for this but I can't find it.

It only has to hold an amp or so but if that were too much, I could simply use a SPDT relay to power whatever was necessary. The alarm is a Digital Guard Dawg and my mystery device needs to primarily power the DEI555U which provides remote start bypass for the vehicle immobilizer. To keep things simple in other areas of the install, I may also have it help with the door lock/unlock. The door locks with a ground and unlocks with a 1k resistor (ground). I hope this helps. Thanks!!!

-hyde

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: September 18, 2009 at 11:16 AM / IP Logged

OK to reinvent Mr. Idiot's crystal ball you've got yourself a VW Polo or Transporter, now get a decent alarm with aux outputs you can set to pulse, time or latch, there are Vipers and Hornets for sale in the UK 'cause that's where you're hiding aren't you, all of the above mentioned have what you want and they aren't an un heard of brand of dubious quality.

KPierson

Platinum - Posts: 3,527

Joined: April 14, 2005

Location: Ohio, United States

Posted: September 18, 2009 at 1:24 PM / IP Logged

Howie,

He is most likely using the DGD system to allow keyless start (which it really isn't designed for, it is designed to be a keyless starter kill).

1A of current is WAY too much power to draw from the system, even though it won't be in the "disarmed" state very often.

One way to do what you are trying to do is to use a Darlington transistor configuration with a decent sized pull up resistor on the base of the first transistor. The pull up resistor will keep the output off as long as the input is grounded (connected to gwa wire) and will allow the transistors to turn on one the ground is removed. This circuit will use a small amount of current when the system is armed as the pull up resistor will be active. This may work to provide a "ground when disarmed" output.

Kevin Pierson

mr_hyde

Member - Posts: 14

Joined: October 09, 2008

Posted: September 19, 2009 at 1:29 AM / IP Logged

Howie, KP is right - I'm using the term 'alarm' to simplify my description. The DGD is what I'm will be working with. Howie, can point me to a diagram and/or a specific product? It sounds like exactly what I am looking for. Thanks!

mr_hyde

Member - Posts: 14

Joined: October 09, 2008

Posted: September 19, 2009 at 1:31 AM / IP Logged

Sorry, meant KPierson please point me to a diagram or product (although howie and anyone else is more than welcome to also). Thanks!

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: September 19, 2009 at 2:21 AM / IP Logged

This reminds me of your earlier post, you're ignoring easily installed regular tried and tested for your own ideas then asking other's to develop it for you, KP should charge you intellectual rights. A normal product from DEI will do everything you want.

KPierson

Platinum - Posts: 3,527

Joined: April 14, 2005

Location: Ohio, United States

Posted: September 19, 2009 at 6:41 AM / IP Logged

A darlington transistor configuration is more something you would build then buy.

I would start with something like this: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=TIP112TU-ND

add a 1K-10K base resistor and a ~10K pull up resistor.

You may have to play around with the exact values to make it do exactly what you want, and you may need to throw some actual current on the output (like a relay) to keep leakage current from activating your bypass.

Kevin Pierson

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