# Voltage Regulator Problem

Discussion in 'The Projects Forum' started by waver, Sep 1, 2008.

1. ### waver Thread Starter New Member

Sep 1, 2008
1
0
I am a newbie here and would appreciate the help. I need some help on a project...the answer is probably really simple, so please be patient.

I need to design a simple (and I mean simple) circuit that will receive a forward biased DC Voltage at the input ranging from 0-100VDC and the output needs to be kept at a constant 1VDC. The key is that the circuit can receive 0-100VDC without any damage but will only take a specific voltage range or exact voltage to pass current. What I mean is something for example that will take 0-20VDC without passing current and at 20VDC will pass current through. At 21VDC it will stop passing current. So it will be specific up to one certain voltage.

I know to use a voltage regulator to keep the output constant but I want something to keep the input inactive up to a certain voltage and then for it shut off again once it passess that threshhold.

Thanks.

2. ### Externet AAC Fanatic!

Nov 29, 2005
776
57
Let's see if these other words mean the same to you...

From zero to 19.99 Volts DC supply, will be open, no current to the circuit.
From 20.00 to 21.00 Volts DC supply, it will feed regulated 1 Volt DC to the circuit.
From 21.01 to 100 Volts DC supply , will be open, no current to the circuit.
And you mean simple. And you are a newbie.
And how much current capable do you want the 1 VDC be ?

Is that right ?

If the source supply voltage is divided by 10 with precision resistors -say 9000Ω and 1000Ω , a precision window comparator circuit (1 chip) would work set to 2.0 to 2.1 Volts, using precise resistors.
The window comparator valid buffered output then energizes a relay that feeds 20 to 21V to your 1V regulator. At all other voltages, the relay remains open.
The window comparator will need a very stable additional DC supply for itself.