G
Glenn Ashmore
Guest
I need to maintain pressure on a hydraulic system within a narrow +-3% band
for some tests but the commercial precision pressure switches are way out of
my budget . I have a 4-20ma pressure transducer that I can drive at 24V
with a maximum 700 ohm shunt resistor (Say 680 ohms). I need a switch that
will turn the pump on when the voltage drops below 4.35V and off when it
reaches 4.45V.
I have been experimenting with an LM1458 dual op amp and some 10K trimmer
pots I had on hand and can get a pair of LED's to light as the input voltage
goes high or low outside the .1V range but I am having a brain freeze on how
to latch a relay on when the low op-amp turns on and off when the high
op-amp turns on. I can change the logic by reversing the op-amp inputs but
any way I do it the pump will turn off as soon as the pressure gets in the
range. There will be no deadband so the pump will cycle rapidly.
Any suggestions?
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com
for some tests but the commercial precision pressure switches are way out of
my budget . I have a 4-20ma pressure transducer that I can drive at 24V
with a maximum 700 ohm shunt resistor (Say 680 ohms). I need a switch that
will turn the pump on when the voltage drops below 4.35V and off when it
reaches 4.45V.
I have been experimenting with an LM1458 dual op amp and some 10K trimmer
pots I had on hand and can get a pair of LED's to light as the input voltage
goes high or low outside the .1V range but I am having a brain freeze on how
to latch a relay on when the low op-amp turns on and off when the high
op-amp turns on. I can change the logic by reversing the op-amp inputs but
any way I do it the pump will turn off as soon as the pressure gets in the
range. There will be no deadband so the pump will cycle rapidly.
Any suggestions?
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com