current handling of diode?

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=76176
Printed Date: May 21, 2024 at 8:07 PM

Topic: current handling of diode?

Posted By: dmangru01
Subject: current handling of diode?
Date Posted: April 13, 2006 at 12:16 PM

I want to hook up my headlights to my alarm but each side has thier own wire, so i'll have to energize both. I want to do this using one relay. So to do this I am thinking I can just use diodes to isolate each headlight wire when I'm hooking them up to the relay. However I'm not sure as to how much current will flow therefore what rating diode I should use.

The bulbs are 9007 so they are 55 watts each. Now what I was thinking is that each bulb would use about 4.6 amps (using P=VI). Assuming this formula applies, could I use 2 3-amp diodes in parrallel so that it would handle 6 amps and be enough to handle each bulb?

Replies:

Posted By: xtremej
Date Posted: April 13, 2006 at 3:25 PM

I would have to suggest buying a higher amperage diode. I have not diode isolated a headlights but I use 10 amp diodes just for parking light isolation.

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Posted By: firstrax
Date Posted: April 13, 2006 at 4:54 PM

You should also consider power dissipation of the diode. Often you can be well under the current limit but exceed the diodes power dissipation rating.

To calculate the power dissipation (the heat the diode will generate) take the diodes Vf and multiply by current. Then check the diodes specs to make sure it does not exceed its rating.

In high power applications use a schottky diode. The voltage dropped will be 1/2~1/4 of what a regular diode will drop and far less heat generation.

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