0081 - Kit Build: Build and improve an LM317 Based Variable Linear Power supply

In this video we will build an inexpensive kit that offers a variable linear power supply, a logic probe and a continuity tester all in one easy to build kit. However, we make a few simple and inexpensive modifications we fell make it more useable and an overall better instrument.
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[@frenchcreekvalley]

Since, as previously mentioned in the comments, the inverter chip takes a lot of power, I added a switch on mine to remove power to it.

[@uni-byte]

Sounds like a good mod.

[@chrislaskey6261]

I built the almost exact same kit. I scrapped all the logic probe stuff. I haven't needed a logic probe for decades. When I found out it crow-bared at 150 mA, and the LM317 with a heat sink can sink 1.5 amps, I scrapped the plug and transformer, and in stalled a DC adapter socket. I use an old Laptop power supply that can produce 2 A @ 16 volts DC. It works so well, I actually use it instead of my big bench supply. It weighs nothing, it's easy to move around, and it's good for most stuff I need, and it can sink a fair bit of current for short periods of time before it gets too hot. I like that you added a power switch, and those banana lug terminals. I might just change mine now. Thanks.

[@uni-byte]

Interesting mods you did. I had though of putting a beefier transformer into it but could not find anything appropriate. I bet it gets pretty toasty if you draw 1.5 amps @ around 2V though.

[@t1d100]

Thanks!

[@uni-byte]

Thank you!

[@ivolol]

Perhaps the mains filter cap can't hold up the rectification above 150mA?

[@uni-byte]

That might also be the case, but the transformer is only rated at 2VA (probably less in reality) so even if the cap was more than up to the task it would still begin to loose ground around 150mA.

[@jakubczajka4275]

£3.31? This business can't be profitable.

[@uni-byte]

Well, if they can make them for £2.00 then they make a 65% profit. Sell 10,000 of them and you have £13,100. Sell 100 other different kits and next thing you know your driving a nice Mercedes. But yeah, insanely cheap, eh?