Thermal camera on a variac

I'm not sure where Christoph got them. Possibly eBay?

Big Clive

I'm curious about those lenses mentioned. can anyone tell me where they are from ?

Drachnien

Tempting as it is, I don't think it would get much use here.

Big Clive

Very interesting, thanks Clive. I have a 8A variac sitting in the garage that was surplus to requirements when we decommissioned the anechoic chamber at work. Any interest for you?

I dont think Clives Variac has a secondary at all, It's one straight coil tapped at both ends and about 20 turns in form either end. Usually mains connected to one end and the the one Near the other end. If you turn the dial past the last tap you can get another few volts but still all on the primary with no isolation. Others mentioned here in the chat probably had an additional isolation coil beyond that.

Jim

who would of thought that. very interesting. The I wonder if you turn the variac to a different location will the secondary hot spot move the same distance?

DC Allan

I use Kapton tape on some surfaces to get a better reading.

Big Clive

Are you on 120 Volt and looking for about 100 Volt? You could use a 24 Vac isolation transformer and turn it into an autotransformer. The construction will be: 120 V -24 V = 96 V. Make sure the transformer can handle the current you need. The current of the secondary side is the one you need to be looking at. By the way if you wire the transformer the wrong way you will get 120 V + 24 V = 144 V. Check with a meter before connecting your load.

Frank

In other words, it's an autotransformer with one primary winding, one variable secondary winding and a couple of shorted one-turn secondary windings?

MrTridac

Regarding the thermal imaging, as im sure you already know anyway but hey. It depends on the surface and how much it reflects heat, something like bare metal can give you a false reading due to the camera reading a reflection and not the surface itself, painted or laqured metal does help improve the reading, you can change the emesivity depending on the surface and material type to get the best reading. Sometimes just putting some masking tape or electrical tape on a surface will help get better readings on shiny surfaces.

James

It was definitely too clean, and I should adjust the G-code setting to 50C for the base.

Big Clive

They can be used for testing things like 120V equipment or gradually ramping voltage up to stuff to see if the current goes too high, as opposed to direct mains voltage.

Big Clive

I installed one of the self adjusting variacs a very long time ago, when computers were apparently so sensitive they would crash if the supply voltage wasn't right.

Big Clive

Nice thermal piccie, thanks Clive. We have a few variacs kicking about. Once we had use of a Claude Lyons motorized variac with RMS sense. Set and forget. Quite nice. Far cheaper than a power amp back in the day ... and even now. We're thinking of getting a Kikusui. We've enhanced two of our variacs with isolation, making them pretty useful for test and development. I have a small one at home during lockdown. The whole isolation thing ... it's less about safety and more about convenience. Not blowing up programmers. Not latching up PC ports. But working alone at home I take more care. Sometimes I stand in a laundry basket for isolation.

Mike Page

John, other than to use for prototyping and designing circuits, what else would you use a variac for? I have seen them but never used them or heard them discussed in real world application terms.

The Tinkering Shed

I picked up a few smaller Variacs from eBay for lighting. W2 was the model. I use them for my basement and garage lighting. I have a pile of 20 watt driver-on-board led’s and without significant cooling they don’t last. I attached a few to old fluorescent fixtures thinking it would sink some heat, it didn’t work well. The new setup is thicker aluminum, and a variac to drop the voltage to 100 volts. The light is just slightly dimmer and cobs are running at 45c. I wish I could get a cheap plain transformer that just drops the voltage to 100 but at $20 for a used variac, this will work. Being a hoarder, my new light panels are the old aluminum tops from a round swimming pool. They seem to work well with 5 cobs per 4 foot section. I thought all 5 should draw half the wattage at 50 but I’m only drawing 30 watts per 5 units. Either my math sucks or I don’t understand the electronic drivers very well.

Jim

A layer of glue on your build plate does two jobs, it holds onto the part but it also doesn't hold onto the part too well and tends to release when cool.

Mike Hanley

Read a few posts on printer chats about glass delaminating, usually the responses are the temp was too high and the glass was too clean, i.e nothing to create a separation layer therefore it forms a thermal bond. I have a magnetic bed and occasionally had a print which just didn't want to lift and left it's mark on the bed, some people have reported the PEI top surface tearing off if they go too close or too hot. I installed a BL touch z probe to achieve consistent first layer height, that has made a huge difference to lifting and first layer adhesion.

The Tinkering Shed

Have never used a variac and have only ever seen then on a shelf in the college, what are the typical uses?

The Tinkering Shed

I would love to have a small variac. Well have them all over at work. Great stuff!

Michael Thompson

That's still a very useful resolution at a very good price. It'll get even better with time.

Big Clive

I ordered magnetic build plates right after it happened.

Big Clive

Have a look at the flexible build plates. A saviour when I printed a foamy whoofler on my resin printer.

evilution

I have a 10a variac, and I have had it apart, as I banged it around too hard once, and smashed the brush! I did get another one made, and after some handywork, got it perfect! It doew seem to just short, but I think the resistance of the carbon stops it being too nasty. Also, on this big one, the entive brush assembly is a large alluminium heatsink! so it expects to get pretty hot undr load!

William Taylor

You inspired me to take some thermal images of my 2kVA (according to the ebay seller anyway...) variac. It takes about the same amount of total no load power as your much smaller one, despite also having a shorted turn at the brush. Pics here: https://imgur.com/a/9bFDyNm I just counted and mine has about 165 turns in the line to neutral part of the winding, or about 0.72V per turn

John Hiesey

Interesting. I just got a cheap thermal camera from banggood, definitely not at all comparable to FLIR but useful for finding hot spots none the less. https://www.banggood.com/Portable-Handheld-Infrared-Thermal-Imager-Thermal-Imaging-Camera-2_4-Inch-24+32-Resolution-Digital-LCD-Display-Thermometer-Measurement-Instrument-p-1445287.html

Peter Stevens

Cool. Or rather, cool in how it's very specifically not cool :)

Nani Isobel