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Variable votage regulator

Superjezz

Apr 1, 2015
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I'm looking to make a voltage regulator for a gold detector using A LM337T regulator. I need it to take a 12 volt battery and lower it down to 6.8 - 7.8 volts adjustable. Can anyone here help out with a design or schematic please?
 

Superjezz

Apr 1, 2015
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I was given this design. It was for a LM350T but I didnt have one. I used a LM337 instead and got a lot lower voltage than I need. Would the different regulator make the difference? If so can I get an update to this to use the LM337T.
 

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Gryd3

Jun 25, 2014
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I was given this design. It was for a LM350T but I didnt have one. I used a LM337 instead and got a lot lower voltage than I need. Would the different regulator make the difference? If so can I get an update to this to use the LM337T.
Umm... it is ALWAYS a good idea to check the data sheet. One regulator is a positive voltage regulator, the other is a negative. They are not and cannot be replacements for each other. (Additionally, many data sheets actually provide sample circuits that you could use)
 

davenn

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Sep 5, 2009
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As Gryd3 was alluding to ... your LM337T is a negative regulator, swap it for a LM317T

cheers
Dave
 

Gryd3

Jun 25, 2014
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As Gryd3 was alluding to ... your LM337T is a negative regulator, swap it for a LM317T

cheers
Dave
I guess it would have been more helpful to actually post which was which and a proposed solution :s
Thanks for that Dave.
 

Gryd3

Jun 25, 2014
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Just use the negative regulator in the negative line:
View attachment 19510
And it's very important to remember that the 'Positive' side will be 'common'

*You may know that most cars have the negative of the battery tied to the chassis. This is the 'common' for those vehicles.
Some cars however use a positive 'common' which can add some confusion. For example, when installing a stereo the case is designed to be used in a common negative setup so in order to properly install it you need to make sure that the case does not touch the chassis of the car or it will short out.
So. If this project is to be used in an automotive situation where the negative is connected to the chassis, you need to make sure that the negative from your regulator never touches the chassis or any other negative.
Keep us posted and we can give more details.
 
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