# Potentiometer for VDC attached to AC-DC converter

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#### rexdino5

Joined Feb 2, 2016
4
So, currently I'm needing 120Volts but I'd rather use DC instead of AC for safety concerns. Currently I've got a planned setup to use a 8A/400V full bridge rectifier with a capacitor of 100uF rated at 200V to smooth out the voltage. I also wanted to put a Potentiometer so I could control the amount of volts for the output. I intend to use this for multiple projects. I did some stuff on multi sim and it seems I would be putting 125W of energy into the Capacitor. The main question is how and where would I get a potentiometer for 120VDC and what fuse should I use?

-Jimmy Tran

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#### #12

Joined Nov 30, 2010
18,223
Absolutely, positively, no.
This circuit is not only dangerous and incredibly inconvenient, it is forbidden on this website.
Have you done any math on the amount of power you will have to dissipate in resistors to use this supply for anything useful?
Try saying what you need instead of what you want and we can probably hook you up with something safe, practical, and convenient.

#### rexdino5

Joined Feb 2, 2016
4
I have planned to connect 21.26 Ohms of wire up. I'll be using Nichrome 60. 60 inches of it will have a resistance of 21.26 Ohms and I need to about 656Watts to heat the Nichrome up to 2000 Degrees Fahrenheit. If there is a safer way to go about getting 650-700 Watts into nichrome wire using DC voltage, any suggestions would be appreciated.

#### #12

Joined Nov 30, 2010
18,223
Your goal is to heat nichrome? Why use DC when AC is what comes out of the wall receptical and it works just the same for heat?
Why rectify the 120 VAC into 170 Vdc and try to get it back down to 120 VDC?
Do you know the capacitor will charge to 170 volts when you do that?

#### ScottWang

Joined Aug 23, 2012
7,212
The owners of All About Circuits has elected not to host discussions of transformerless threads.

Transformerless powersupplies are not allowed over here.
See point 6 of the user agreement: