voltage reducer formula

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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=21788
Printed Date: May 15, 2024 at 1:35 AM

Topic: voltage reducer formula

Posted By: russau
Subject: voltage reducer formula
Date Posted: November 22, 2003 at 1:14 PM

what is the formula for reducing a 12 source(battery) to run a 9 volt device. i know i need to also install a voltage regulator.

Replies:

Posted By: HotRod53F100
Date Posted: November 22, 2003 at 9:02 PM

What are you connecting and is it a constant current draw? The formula is E=IxR (voltage = current x resistance) if the current changes, the resistance required changes also. If it's something simple like a light, it will be easy to figure out. You need to know the current draw or the wattage. If it's something like a portable CD player, go to Radio Shack and buy a converter..it will be easier.

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HotRod

Posted By: russau
Date Posted: November 23, 2003 at 6:52 AM

thanks hotrod! thats what ill do!

Posted By: xetmes
Date Posted: November 23, 2003 at 7:53 AM

yea you dont really want to use any voltage divider setup although you can if you know the current draw of the load. A linear voltage regulator can be used, it may get hot so i recommend a heatsink, you can also use a zener diode, i think 9.1 V is a standard value zener...

Posted By: russau
Date Posted: November 23, 2003 at 10:02 AM

thanks xetmes, what im want to do is, use a 12 volt batt to power 6 or 9 volt loads for prolong times. maybe 6 hours or more. and i wanted the extra useage from the 12 source. that way by the time the voltage starts to drop and effect the loads ability to perform its proper function, i would be done for the day. and recharge if needed the battery for the next days fun! thanks for your help! it should be easy to make and probly it is already ava. at radio shack if id get up and look for it!

Posted By: xetmes
Date Posted: November 23, 2003 at 11:17 AM

hmm the problem with using zener diodes and voltage regulators in applications like this is they waste power, thats why they get hot.. I though this was going to be put in a vehicle where the wasted power is not really a big deal.. If you want a more effiecient way you could oscillate the 12V and step it down and rectify it, but for just 3 volts it would not be worth it... so i guess your best bet is still a voltage regulator or zener.. dont ask me why i typed this hah posted_image

Posted By: mobile E
Date Posted: November 25, 2003 at 10:37 AM

yeah defenetly what he said

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