DIY Variac Build

[NickH]

Hi Guys,

Attached are pictures of my Variac that I have been building over the last few weeks...

It's 8 Amp & I went for a digital voltmeter (blue) and an analogue amp meter, so I would have the accuracy on volts & the diagnostic movement on the amps...

The case was probably the hardest bit, we cut the holes on the CNC machine & then it was a few days of sanding, painting, sanding, panting etc before I could get the thing together & do the wiring... my m8 made some great little aluminium spacers on his lathe to go on the transformer bolts to keep the spacing equal between the transformer & the face.. It was quite a fun project!

Total cost was around £140.00

Cheers

N

[NickH]

[tedmich]

very pretty! I had never thought of such a fancy implementation of the old variac... for me a nice circular scale with approx. voltages mocked up with illustrator and then laminated and affixed behind the knob would be helpful for reading from across the room before the power flows and the LED meter lights up.

Did you get the meter online? Its amazing how cheap meters are on the ebay, I am buying a 600VDC meter for my HT supply for about $12... Also PID temp controllers are ~$30.. thank you china!

[NickH]

for me a nice circular scale with approx. voltages mocked up with illustrator and then laminated and affixed behind the knob would be helpful for reading from across the room before the power flows and the LED meter lights up.!

The transformer came with a metal scale as a plate that you screw on as it happens, I just didn’t like the look of it that much & I always power up on zero anyway..

Did you get the meter online? Its amazing how cheap meters are on the ebay, I am buying a 600VDC meter for my HT supply for about $12... Also PID temp controllers are ~$30.. thank you china

Yep, both meters from eBay & both from China



N

[Enzo]

VERY nice work. I like it. Get a photo with a bright 238 or something in the voltmeter display.

Looks real sturdy, good support for the transformer itself, not just relying on the front panel. I like the finish nuts on the front panel.

ANd good thinking on the meters.

[andrew_k]

Wow, excellent! Nice and compact, unlike the monstrous old steel box my variac is in.

[Rockn]

Variac

Do you have a parts list and schematic of this project? I want to make one if it is cheaper to do so than buying one.

Thanks

[Bill Moore]

I didn't get Enzo's display comment the first time I read his post, but realized this time what he meant.
When I worked for the power co., I used a variac to control a HV transformer we set up backwards to check the ma draw on the line truck insulation. Set it up 114.5V lnput for 69KV output, had the line scribed on the cheap analog meter, while monitoring with a simpson. It really worked great, and saved a lot of time, for the guys didn't have to drive to a substation to test. But I didn't think about circuit protection, and had a 10 amp breaker on the input in the main panel. One day a driver raised his boom and energized the tester with out extending the fiberglass boom, really smoked the thing. When I rebuilt it, I added a 3A pop off breaker at the control box.

[Enzo]

I merely meant that the photo would look cool if there was some actual voltage reading glowing on the display.

[Bill Moore]

Yeah, but you realized that NickH would not read 120V on his wall outlet, it went over my head the first time.

[Enzo]

Oh, I get it now.