Circuit for keeping voltage below a certain amount

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VacuumTube194
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Circuit for keeping voltage below a certain amount

Post by VacuumTube194 » Mon Feb 07, 2011 9:58 am

I need a circuit that will maximize a voltage. What I mean is the voltage may vary, but I want it
so if the input goes above 30 volts, then it will send 30 volts only through the output. I don't want the
voltage cut off (like a fuse) if it goes above that amount. Does anyone have any suggestions?

dyarker
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Re: Circuit for keeping voltage below a certain amount

Post by dyarker » Mon Feb 07, 2011 10:45 am

how much current we need to dump?
Dale Y

VacuumTube194
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Re: Circuit for keeping voltage below a certain amount

Post by VacuumTube194 » Mon Feb 07, 2011 1:15 pm

About 50-100 miliAmps.
dyarker wrote:how much current we need to dump?

Robert Reed
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Re: Circuit for keeping voltage below a certain am

Post by Robert Reed » Mon Feb 07, 2011 9:15 pm

What you want is called a "Clamping Circuit". Google that up for a wealth of information on the subject.

Dimbulb
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Re: Circuit for keeping voltage below a certain amount

Post by Dimbulb » Tue Feb 08, 2011 8:44 pm

You could use a series regulator.
First build a standard zener circuit to get a tiny 10mA of 31 volts
this has little noise and can be filtered if it becomes critical.

Try to have at all times at least 33V unregulated.
then when add a series regulator you can adjust it to exactly 30V

Dimbulb
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Re: Circuit for keeping voltage below a certain amount

Post by Dimbulb » Tue Feb 08, 2011 8:56 pm

sorry for having to post twice
this forum has the edit function disabled and the FAQ is incoorect !!!
time to look for a different forum

the series circuit should have a transistor
http://www.tpub.com/neets/book7/27k.htm

sorry again the edit function is really important
to continued success of this forum !

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haklesup
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Re: Circuit for keeping voltage below a certain amount

Post by haklesup » Mon Feb 14, 2011 5:14 am

A 30V Zener diode should do it all by itself as a clamp. 1N5363B should do the trick. its a 5W part and can dump a whole lot more than 100mA if need be.

I edit all the time, not sure why you can't. It used to be having the wrong skin would eliminate certain functions but I don't see skin selection in the control panel anymore. Try PM the sysop for a fix. My edit button is in the upper right corner of my posts (last sentence added by edit)

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Bob Scott
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Re: Circuit for keeping voltage below a certain amount

Post by Bob Scott » Mon Feb 14, 2011 6:36 am

All you need is a 3 terminal voltage regulator with low dropout. (If you don't mind a slight bit of dropout.)

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