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I am attempting to make my own adjustable voltage supply that provides a positive voltage (anywhere from 0 to +200 VDC).

The sections I have devised so far are able to provide 450 VDC, however I need an exclusively positive voltage and one that is 200 VDC or less (voltage going to the load will be 0-200 VDC).

Unfortunately, I'm not too experienced with wiring potentiometers for this kind of a situation. To my knowledge, this is how a potentiometer would usually be included into a circuit (please note that while this diagram uses a motor, I will not be using one in my set up): enter image description here

If I wanted to only have a positive voltage going to my load, should I simply ground the negative lead shown in the picture?

P.S. If people are curious about the load, it is simply a grid bias for a thyratron, nothing terribly advanced that requires anything beyond 0-200 V.

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  • \$\begingroup\$ You need to learn more accelconf.web.cern.ch/accelconf/pac97/papers/pdf/7P083.PDF and define requirements better \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 10 at 23:21
  • \$\begingroup\$ The motor in your image should be replaced by a thyratron. OK. There's still something which resembles a battery, maybe a car battery, What kind of battery you have planned to use and have you already selected the thyratron? The case would be easier if you revealed the selected types. Especially useful would be to know the intended functionality which is achieved if you feed adjustable 0....+200V to the thyratron. \$\endgroup\$ – user287001 Jan 10 at 23:22
  • \$\begingroup\$ that is not a potentiometer ... it is a variable resistor \$\endgroup\$ – jsotola Jan 11 at 8:35
  • \$\begingroup\$ Does this answer your question? how to reduce DC voltage using resistors? \$\endgroup\$ – The Photon Jan 11 at 16:24
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The neutral name of this 3-terminal variable resistor maybe should be something like "variable resistor with three terminals". Depending on how you wire it (which terminals you use), there are two basic configurations:

Variable resistor (rheostat). This is your connection. You use two terminals - one of the end and the middle (slider). In this case the resistance changes and you can adjust the current (through something like a motor).

Potentiometer. In this configuration, you have to apply the input voltage across the whole resistor (i.e., between the end terminals) and to take the output voltage between the middle terminal (slider) and one of the end terminals.

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I'm not sure of the current requirements of a grid bias, but if they're small, like a couple mA or less, a potentiometer would work. You would need to ground the lead on the right to generate the positive voltage though, because all a potentiometer really is is a variable voltage divider. This is the internal schematic of a potentiometer:potentiometer internals

You'd typically ground the left wire in this specific image, otherwise you just get a variable resistor.

It is important that your potentiometer be rated to handle the high voltages you are using, not all pots can handle 200V+

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  • \$\begingroup\$ To confirm, I could use the set up that I included, all I'd have to do is ground the negative lead on the battery? \$\endgroup\$ – James Li Jan 10 at 23:40
  • \$\begingroup\$ Yes, all you grounds should be connected, the battery GND, the last potentiometer lead GND, and the thyratron GND should all be connected, otherwise there is no reference. \$\endgroup\$ – ccolton Jan 10 at 23:45
  • \$\begingroup\$ If I wanted a negative voltage rather than the positive voltage I was discussing previously, could I put the potentiometer set up on the negative lead of the battery and ground the positive lead of the battery? \$\endgroup\$ – James Li Jan 10 at 23:49

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