diode blocking circuit

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=93890
Printed Date: May 21, 2024 at 5:41 PM

Topic: diode blocking circuit

Posted By: silentblackhat
Subject: diode blocking circuit
Date Posted: May 14, 2007 at 1:35 AM

I am wondering if this is correct.

This is the way I want to wire something up that will activate a relay but i want them isolated. Input #1 is just a 12V switch from the 12v car battery. Input #2 is from a CB radio switch. I want to be able to turn on input #1 to activate the relay but not to 'leak' into the input #2. I placed the diode in the circuit there because when I turn off input #2, if there isnt anything blocking the voltage from #1, it will keep #2 on(because it would keep the #2 device on if it has a 12v supply to it)

Also, what types of diodes will work to do this if it is wired correctly? Will any diode work that I can get at radio shack? I for a 2 pack of rectifier diodes that has a 3amp rating

posted_image

Any help is appreciated.

Replies:

Posted By: KarTuneMan
Date Posted: May 14, 2007 at 10:11 AM

In the member list section, look up hot water wizard. This guys knows........

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Posted By: dualsport
Date Posted: May 14, 2007 at 1:58 PM

Yep-

As long as your input #1 is always at 12V, the diode can be any run of the mill 1A (1N4001).

If at any point you might want to close the switch for #1 and it's not at 12V, then you may have problems blowing something out (either the diode or whatever you're using to drive #2 with), if it's very low impedance, because it may act as a short to ground, depending on where it's coming from. If #1 input is always at 12V, no worries, because the diode will only be driving the relay coil, nothing more.