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diode math, please help

Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=28413
Printed Date: October 31, 2024 at 6:43 PM


Topic: diode math, please help

Posted By: markcars
Subject: diode math, please help
Date Posted: March 15, 2004 at 2:21 PM

does anyone know what happens when you put 2 diodes in series or parallel? Does the amperage change? Does the voltage change? Does the capacitance change? The answer is more than likely a yes. So how is the change calculated? Is it same as resistors or differently calculated? Any electronic engineer, genius or guru out there? please help.



Replies:

Posted By: xetmes
Date Posted: March 15, 2004 at 5:37 PM

Two diodes in series will increase the voltage drop, sum of the two. junction capacitance will decrease, current max is of the lowest one.

Two diodes in parallel will have the voltage of a single diode, current handling will be the sum, junction capacitance will increase





Posted By: markcars
Date Posted: March 15, 2004 at 7:03 PM
Just wondering. I put 2 diodes (1N4003's) in parallel for my door trigger via domelight sense -ve. Normally they put 1 diode. My alarm does not trigger at all. Are you sure 2 diodes in parallel will result in no more voltage drop than a single diode and allow only double the current passage??




Posted By: xetmes
Date Posted: March 15, 2004 at 7:17 PM

hmm not sure why you would use 2 4003s unless you plan on drawing 2A with 200V across them...

They should work the same, are you sure the polarities are the same, if one is opposite it will not work. Does it work with just one? Did you see what is happening with a DMM?





Posted By: markcars
Date Posted: March 15, 2004 at 7:29 PM
actually if the polarities were reversed, since they are in parallel, they would have no effect other than a shorted/straight wire. The reason why I used 2 was just in case one failed (cut off) the other would still let the voltage pass back through the workign one so the sensor gets its -ve sense.

I have not tried with one. the weather was so cold that all my fingers and toes and myself were turning numb. Hopefully next weekend if the weather is bearable, I will check and investigate for reals with my DMM. Till then I just have to wonder. Most probably I won't even use the dome light, but the actual door triggers even thought it is going to be a pain in the but.





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