Negative volts input to optocoupler for it's infrared diode?

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russwr

Joined Aug 29, 2017
35
How to set up negative -130 volts pulsing for input to the internal diode of optocoupler 4N25? The voltage has to be reduced way down and also reset for positive to the infrared diode. Would extra diode added as the anode to pin work , or should I use voltage divider resistors for center point as floating reference using the positive ground and center point minus?
 
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crutschow

Joined Mar 14, 2008
34,044
How to set up negative -130 volts pulsing for input to the internal diode of optocoupler 4N25?
You just ground the anode of the input diode and apply the negative signal to the cathode through an appropriate resistor.
What is the load for the 4N25 output, as that determines how much input diode current you need.
 
Last edited:

WBahn

Joined Mar 31, 2012
29,857
How to set up negative -130 volts pulsing for input to the internal diode of optocoupler 4N25? The voltage has to be reduced way down and also reset for positive to the infrared diode. Would extra diode added as the anode to pin work , or should I use voltage divider resistors for center point as floating reference using the positive ground and center point minus?
It's almost impossible to tell what you are talking about.

Draw a schematic of the different things you are considering or wondering about. Don't make people guess.
 

MisterBill2

Joined Jan 23, 2018
17,790
Use a diode to isolate the load from the pulsing voltage source, and a capacitor to stabilize the resulting charge voltage between pulses. Then use a series resistor to keep the current within the limits of the optoisolator. Then connect the correct polarity to the optoisolator LED side. That is as simple as it can be.
 
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