Electrical Help

Let me preface this by saying I don't know of any op amps that work over 40
VDC.

The normal way to do what you want to do is with a special op-amp circuit
called a comparator. You compare the actual voltage to a "reference
voltage" and te op-amp amplifies the difference. An analog filter would
give you the +/- 3V dead zone, and an H-bridge would allow you to turn the
motor.

On second thought, This would be a great project for a 2$ PIC
microcontroller and an A/D Converter. Less Chips + Less Cost = More Cool!



----Original Message Follows----
From: STAN MCDONALD <SMCDONAL@...>
Reply-To: CAD_CAM_EDM_DRO@egroups.com
To: "CAD_CAM_EDM_DRO@egroups.com" <CAD_CAM_EDM_DRO@egroups.com>,
modeleng-list <modeleng-list@...>
Subject: [CAD_CAM_EDM_DRO] electrical help please???
Date: Fri, 04 Aug 2000 09:18:42 -0700

Hello list.
I am trying to come up with a device that I can feed 100-280 volts DC
into and then if the voltage is less then a preset voltage (around 120
DC) then it would inturn connect a separate DC power source in one
direction to a DC motor, If on the other hand the voltage was higher
then the preset 120 DC it would connect the same separate DC source to
the motor in the opposite direction.

This would inturn drive the dc motor clockwise if voltage is to high and
counterclockwise if the voltage was to low. If the voltage is the 120
volts +/- 3 volts nothing happens.

I tried this idea with relays but it didn't work out because the relay
would turn on at one voltage and turn off at a different voltage.

Does anyone here have a good way to make such a device?
Thanks
Stan



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