wiring leds

Prolly a stupid question but how many LEDs can an alarm power by tapping off of the original LED. whats the best way to add more LEDs like say 5 or more plus I got the 2 LEDs that go into the headlights so keep in mind thats all gonna meet up too. Thanks for your input!

Most alarms will tell you the most LED's it can handle in the manual. LED's are usually wired in series, not parallel....

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Mike M2
Tech Manager
CS Dealer Services

mike this alarm doesnt say the most amount and i dont know what it means when you said LEDs are wired in a series not parallel thanks

Most will hold around 6. Parallel is when all the negatives are ties together and all the positive are tied together. In series, one negative is tied to the next LED positive and done this way thruout all the LED's.

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Mike M2
Tech Manager
CS Dealer Services

can you use a relay and get more power from the battery and have more LEDs ?

The maximum number of LED's you can drive from the alarm will depend upon the transistor used in the unit. It could be one or more. If there is a number on the transistor, you can look up the specs through a quick search or sites like Digi-key . A typical LED draws about 20 mA on average, so you can use that as a reference to determine if you are drawing more current than the transistor is able to supply. I would advise against using a relay to control an LED since it may not switch quick enough to flash the LED reliably.

Another thing with regard to adding a relay. Do you actually want to listen to the constant clicking of the relay?

Also most alarm LED's and Mike M2 could probably correct me here run on 2.5-3volts one Italian alarm even runs the red feed as the neg side so forget relays. I believe DEI once showed a diagramme running 6 or 8  connecting both in seriesd and parallel. Oh why do novices bring in relays as if they were a magic cure all.

Sorry, printing error seriesd should of course have read seiers and the other point is with the high brightness LEDs  1 placed high in the dash (inst cowl pointing out through the front window as an example) is usually more than adequate.

I've lost it!  Meant to write SERIES 

Howie, you DO have an edit button at the bottom of your post, if of course it was the last post in the thread.

I wouldn't think switching speed would be a concern at all as most relays switch in the low mS range - plenty fast enough for an alarm LED.   The issue here, though, is current draw.  If you use an electromechanical relay you're going to kill your battery in a short time.  If you use a reed relay you will get better results, but the ideal component would be a transistor - extremely small current draw and no significant "wasted" current.

The other thing to think about is the LEDs you are going to use.  If you use LEDs that draw 20mA and you wire 5 of them up that would be a significant additional load to the battery (roughly 25mA average draw with 25/75 on/off cycle while flashing). 

I, personally, would look for LEDs that are under 10mA a piece and drive all the LEDs in parallel off of one transistor (like a 2n3906 assuming the LED control output is (-)). 

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Kevin Pierson