Current Limiting Isolation Transformer

Inspired by an invention of Mr. Carlson´s Lab

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Having been inspired by Paul´s invention (see the link) I decided that I needed one too. The basic build is very similar, but I did not want the light bulbs exposed so that I could stack things onto it. So I put the bulbs inside and added voltage and Ampere meters for monitoring instead. I also added some relays to control the 120/240 VAC outputs and some switches to set the current limiting from 0.25A to 1A in four steps and also change the Ampere meter range between 1A and 10A (current limited and unlimited). To preserve Paul´s idea of becoming immediately highlighted (literally) when a problem occurs, I put in a stainless steel mirror for the back panel which reflects the bulbs lights up through the open top.

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Paul wrote 08/17/2020 at 21:15 point

Really nice build! what kind of extrusion is that?  Just note, it's not Mr. Carlson's 'invention'; The concept has been around for decades, and Tektronix made a few of them.  I'm not sure if they were ever sold as products, or just for internal testing, but the Tektronix TU-75 is definitely one of my 'can't live without' pieces.

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Donnie Agema wrote 08/17/2020 at 21:26 point

Thanks for the correction, Paul. I don´t believe the TU-75 offers mains isolation, at least not as far as I can see in the schematic.

The extrusion came from an old mainframe of a Norwegian company I used to work for (Norsk Data).

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Paul wrote 08/18/2020 at 01:50 point

Ah, you are absolutely right, thank YOU for the correction :)

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Dan Maloney wrote 08/17/2020 at 20:14 point

Definitely looks like something from Mr. Carlson's lab. Love the front panel layout!

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Donnie Agema wrote 08/17/2020 at 20:37 point

Thanks, Dan. I´m kinda proud of it. Never dreamed it would come out looking so good.

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