Alarm led help?
10-06-2011 | 08:22 PM
#12
JK Freak
Joined: Sep 2011
Posts: 911
Likes: 6
From: Las Vegas, NV
mmmh, not really... 
you need an inverter relay.
What you need is:
1x DPST relay (smallest will do... a LED is a very small load!)
1x 12V-rated LED
1x small resistor
You want to wire your LED as per the yellow light in the "power to turn on" circuit; the ignition is playing the role of the "switch" here:
Attachment 204953
(ignore the green light)
So:
1) tap + wire from constant outlet in console, put in on "30" on the relay.
2) tap + wire from switched outlet in dash, put it on "85" on the relay.
3) tap - wire from one or the other, put it on "86" on the relay.
4) take LED short side (-), put it in line with a small resistor, then on "86" as well to go to ground.
5) take LED long side (+), put it on "87a".
6) cut pin 87, it is worthless here.
Here is how it works:
Attachment 204955
1) When the key is in the "acc" or "on", it will give current into relay passing from 85 to 86.
The magnet will pull the steel plate and it will no longer contact pin 87a, effectively shutting down your LED.
2) When the key goes back to "off", the current will no longer pass, steel plate will rise and contact will be made with your pin 87a, so LED will light up.
A 30min project, really!
Enjoy!
Mat
P.S.: how to identify LED + and - :
Attachment 204959
you need an inverter relay.What you need is:
1x DPST relay (smallest will do... a LED is a very small load!)
1x 12V-rated LED
1x small resistor
You want to wire your LED as per the yellow light in the "power to turn on" circuit; the ignition is playing the role of the "switch" here:
Attachment 204953
(ignore the green light)
So:
1) tap + wire from constant outlet in console, put in on "30" on the relay.
2) tap + wire from switched outlet in dash, put it on "85" on the relay.
3) tap - wire from one or the other, put it on "86" on the relay.
4) take LED short side (-), put it in line with a small resistor, then on "86" as well to go to ground.
5) take LED long side (+), put it on "87a".
6) cut pin 87, it is worthless here.
Here is how it works:
Attachment 204955
1) When the key is in the "acc" or "on", it will give current into relay passing from 85 to 86.
The magnet will pull the steel plate and it will no longer contact pin 87a, effectively shutting down your LED.
2) When the key goes back to "off", the current will no longer pass, steel plate will rise and contact will be made with your pin 87a, so LED will light up.
A 30min project, really!
Enjoy!
Mat
P.S.: how to identify LED + and - :
Attachment 204959
10-07-2011 | 05:35 PM
#13
JK Newbie
Joined: Aug 2011
Posts: 61
Likes: 0
From: Montreal, QC
With this simple circuit it will stay on. To make it blink you need a timer chip and capacitor.
In my understanding the resistor is simply because the LED itself might not be a big enough resistance and would "short" the battery and blow the LED with too much amperage. I might be wrong but a small resistor won't hurt.
In my understanding the resistor is simply because the LED itself might not be a big enough resistance and would "short" the battery and blow the LED with too much amperage. I might be wrong but a small resistor won't hurt.
