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need electrical 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=49236
Printed Date: April 27, 2024 at 4:20 PM


Topic: need electrical help

Posted By: placid warrior
Subject: need electrical help
Date Posted: February 02, 2005 at 8:55 PM

not sure where to put this.  I know pretty much nothing about electronics so i was wondering If u guys could give me a hand.  How would i go about with capacitors/resistors or whatever i need, to create something that wont allow the curret to go past 12 volts but will still allow anything from 0-12 volts.  I ask for a couple of reasons...first is because i want to hook up some lights to the alternator so when i rev up the engine they wil glow brighter as the RPMs go up (is this fine? not doing with neons)  also have a problem with an experiment which works at 12 volts but will short or blow fuses at higher voltage.  Anyone able to help me out?  thanks for any help guys.



Replies:

Posted By: daniel2002p
Date Posted: February 02, 2005 at 10:03 PM
ok, first hooking lights up to the alternator is not a good idea and it will not work because your alternator gives out AC voltage and most electronics need DC that run on 12 volts.

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Posted By: placid warrior
Date Posted: February 02, 2005 at 11:49 PM
ok, thanks for the heads up...i heard other people wanting to do it and it sounded like a good idea, but i guess not eh!  but i still require a unit for my other project though so i still need to make one only it doesnt matter if it works from 0-12 volts with this one...a constant 12 volts is all i need while the car is running, but i cant get that since the charging system boosts it up more...do i need to hook up a series of capacitors or can i fint just one that will work...is there a mathematical formula thats fairly easy so i can figure out what kind of capacitor I'll need.  It is just a capacitor that i need right?




Posted By: xetmes
Date Posted: February 03, 2005 at 12:16 PM

capacitor is not really gonna help much for this purpose. If youwant to regulate a voltage below a level like 12V you can use a zener diode, or a unidirectional transient voltage suppressor (TVS), they are basically the same except a TVS can handle more power for a short duration than a zener can.

A zener diode will operate normally untill the threshold voltage is reached, it will then breakdown and will act as a short, so if you put this in parallel with you supply lines you need a resisance to reduce the curent to the zener to keep it from blowing up...





Posted By: placid warrior
Date Posted: February 04, 2005 at 1:12 AM
alright thanks...so whati understand is that i need a resistor and a zener diode, I think a salesman at a place like radioshack could give the the proper ones if i told him what sort of ratings im looking at i suppose, although i havent had much luck with them before.  basically i want a resistor that will block any current higher than ? and a zener diode to keep the voltage at 12ish volts?  or am i sounding like a complete idiot? thanks for helping out though





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