Wanted: good sources to scrounge for electronics

[Golden Sunshine]

I have a PID controller already though it was for controlling my fermenter/chest freezer unit. I could just scrounge eBay for a 40AMP SSR or similar over-spec to keep the heat down on the relay controlling a 10amp element.

But beyond PIDs and Bog Standard Temperature controllers on eBay and China sites I'm not as clued into where locals scrounge for electronics deals on used kit like VARIACs etc. those transformers weigh a tonne so not really excited about shipping one at local post prices.

Is it different depending on region or is there common outlets you electronic tinkers scrounge for parts from?

[Brendan]

Just out of curiosity mate, what on earth do you want a big variac for?

For standard equipment that we use, such as 10Amp elements that you mentioned, SCR/SSR/Triac technology is more than adequate.

As for heat dissipation, an SCR phase angle control module paired with a similar sized heatsink will not be an issue with adequate ventilation, and a little PC fan is even better.

[Golden Sunshine]

My interest in autotransformers is that they are very flexible and useful in many projects outside of just controlling heat output from an element. I'm not too old to have grown up with tubes and old radios and the like so its familiar territory for me. A couple inexepensive components and I can have a quick built fit for purpose charger.

Modern solid state components generate an aweful lot of of heat so I'm not as big a fan of them. I must have strange ears because I usually hear annoying pitched whines from MOSFET controllers and the like. And heat is wasted energy and if it can be controlled all the better, I spend a few hundred extra dollars on computer power supplies that are purpose built to be efficient over the cheap nasty on offer from the local computer parts store as the electricity bill savings alone are worth it in the long run.

I will probably end up going with a solid state phase angle controller but I have a shelf full of purpose built controlers, temperature, humdity, and so on and when I'm not using them for a particular hobby they are stitting there being wasted of their potential so flexibility and multipurpose is my thought process.

Cheers,
GS

[Brendan]

I see GS, if you're are an electronic hobbyist, a variac can be a very useful tool for testing and experiments. Very flexible as you said. I just thought that you were considering that option purely to run a 10amp element or two :) If you have the option and availability of the equipment, well then it's no problem.

Although modern solid state components can generate a lot of heat, their size and cost outweigh a large, heavy transformer for overall cost analysis and efficiency (in terms of producing a commercial device, different story for hobby equipment obviously). Where possible with resistive loads, a zero cross switching topology can be used to eliminate switching losses and noise/harmonics...in our case of heating elements, smoother control is derived by utilising the much less efficient phase angle control which is normally employed for inductive loads due to the phase shift between voltage and current.

In regards to your variac...be mindful of some of the cheap Chinese built devices on eBay. Can get some real shockers on there. I think you're in the right mind to be 'scrounging', as an old well-built variac can last forever if maintained well. I have known of a few electronic shops near where I am which were going out of business due to people not getting tv's and amps repaired so much anymore, and they were parting with a lot of their equipment. You should also keep an eye on eBay for second hand ones that may pop up near to your locality...if you look to RS, you will pay through the nose and I assume as a hobbyist, that is not something you are prepared to do.

Good luck mate :handgestures-thumbupleft:

[Muppet]

This is a bit left field but I have seen a lot of home & industrial electrical gear at the auctions I go to. Pickles auctions are a big player and if you know your stuff I'm sure you could find something suitable. There's a website to find the auctions that suit you, from there you will have to go look. Picked up many bargains this way it's a bit of an experience too

[RuddyCrazy]

Oatley electronics often have some great old stuff going and there store is in Sydney, they do have a website and doing business with them is a pleasure and I have been dealing with them for close to 10 years.
http://secure.oatleyelectronics.com//index.php

They maynot have what your looking for but they have a heap of good bargins so worth checking them out.

Cheers Bryan

[Golden Sunshine]

Thank you for the tips of places to look!