Voltage Switching

 

Hello, I am trying to interface with a device that outputs 24V when
off and switches to 0v when commanded on.  The problem is, I need 0v
when off and 24V when commanded.  I tried to use an opamp as a
comparator to swap the voltages but have not been successful.  Is
there a circuit I can make or is there a device that exists to do what
I require?  Thanks a million.

 

On Tue, 14 Aug 2007 20:12:04 -0700, robert.mcd wrote:


What sort of "device"? How often does the output change, and how much
current do you need to draw?

 

On Tue, 14 Aug 2007 20:12:04 -0700, robert.mcd@gmail.com wrote:


Nobody asks the relevant questions.

But if you are talking signal with not much current and on-off switch
a simple NPN transistor switch will invert the signal for you.

Emitter to ground, base connected to your signal with a current
limiting resistor in series, collector load resistor pulls the voltage
to 24 volts when the transistor is off (24 volts not present on base
resistor) and 0 volts on collector (when 24 VDC is present).
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Thanks, I will give this a go.

 

On Aug 15, 6:07 am, robert....@gmail.com wrote:

Also, consider inverting the signal at the input of your device.  I
can't tell you which way would work better though, because you gave us
so little information.