High voltage voltage controlled linear variable resistor

In summary, the individual is looking for a voltage controlled linear resistor that can withstand high voltages to use in controlling analog circuits digitally. They initially considered using LDR optocouplers but discovered they cannot handle high voltages, so they are now considering using transistor or diode optocouplers. They are seeking advice on which type to choose for a high voltage linear variable resistor intended for a voltage divider. They also mention the possibility of using multiple LDR optocouplers in series to achieve higher output voltage, as long as the LED currents are closely matched and the isolation voltage is high enough. They also suggest using a current source and explain that the LDR only needs to handle a few volts, with the FET taking the
  • #1
coinmaster
41
0
I have some high voltage (300v+) analog circuits that I want to control digitally which requires the use of a voltage controlled linear resistor that can withstand high voltages. I don't expect the current levels to be that high.
I originally settled on LDR optocouplers but it turns out they can't handle big voltages so that leaves me with transistor or diode optocouplers.
As far as I understand it, photodiodes are light controlled zeners and phototransistors are light controlled transistors.
Which one should I choose for a high voltage linear variable resistor meant for a voltage divider?
 
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  • #2
If you put multiple LDR optocouplers in series you would be able to get an arbitrarily high output voltage. You will just need to make sure your LED currents are closely matched. 300V should not be a problem as long as the isolation voltage of the part is high enough.

BoB
 
  • #3
might this help ?
Make a current source...
LDR only has to handle the few volts necessary to bias the FET, FET takes the rest. Voltage across LDR is small compared to 300.
apparent resistance = 300V/current

upload_2016-2-13_19-3-37.png

http://users.ece.gatech.edu/mleach/ece3050/notes/ISources/isources.pdf

see also http://www.vishay.com/docs/70596/70596.pdf
 

1. What is a high voltage voltage controlled linear variable resistor?

A high voltage voltage controlled linear variable resistor is a type of electronic component that can vary its resistance in a linear manner based on the voltage applied to it. This allows for precise control over the amount of current flowing through a circuit.

2. How does a high voltage voltage controlled linear variable resistor work?

Inside the resistor, there is a resistive material that is connected to two terminals. When a voltage is applied across these terminals, the resistive material changes its resistance, thus controlling the flow of current through the circuit.

3. What are the applications of a high voltage voltage controlled linear variable resistor?

These resistors are commonly used in voltage regulators, power supplies, and amplifiers to control the output voltage and current. They are also used in electronic circuits that require precise and adjustable resistance, such as in audio equipment and sensors.

4. How is a high voltage voltage controlled linear variable resistor different from a regular variable resistor?

A regular variable resistor, also known as a potentiometer, is limited to low voltage applications. A high voltage voltage controlled linear variable resistor, on the other hand, can handle much higher voltages without damaging the component. It is also more precise and has a linear response to the applied voltage, unlike a potentiometer which has a logarithmic response.

5. Are there any safety precautions to consider when working with high voltage voltage controlled linear variable resistors?

Yes, it is important to handle these resistors with caution as they can handle high voltages. Make sure to wear appropriate safety gear, such as gloves and goggles, when working with them. It is also important to follow the manufacturer's guidelines and only use them within their specified voltage and current limits.

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