One of My Favorite Building Blocks

RE: One of My Favorite Building Blocks

cstanton — Wed, 19 Feb 2020 15:52:01 GMT

Hah this's pretty cool! I've been meaning to sort out some form of bench power supply myself, until then I'm messing around with various adapters for wall warts which isn't the best way to work o.O it's great to see the reverse engineering you've done here [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-80d34b68-148d-4eb8-a573-2f2674fa337c/contentimage_5F00_1.png:16:16]

RE: One of My Favorite Building Blocks

DAB — Sun, 16 Feb 2020 22:45:47 GMT

Hi John,

I always like your board mods.

DAB

RE: One of My Favorite Building Blocks

ralphjy — Sun, 16 Feb 2020 19:15:51 GMT

It's great that you've found a building block that you've been able to use in a lot of projects. Modifying circuits is a great way to learn about how they really work. Sounds like you've become quite an expert with this circuit. Great to see how you adapted it for so many different applications. It is a bit disconcerting to hear that the TL081's that come with the kit don't actually meet spec functionality. It's nice that this comes as a kit so you can easily swap them out.

Ralph

RE: One of My Favorite Building Blocks

dubbie — Sun, 16 Feb 2020 17:20:17 GMT

I built my own power supply once, for a mobile robot that had 5V 3A stepper motors (I'm not sure why I choose these - they seemed a good idea and were lovely pieces of kit but they were difficult to power and step correctly - I learnt a lot about step motors from these) so made mains to 5V at 10 A. It was a giant transformer with 2N055 power transistors for the regulation, plus a massive capacitor, in a metal box. It weighs a ton. It still works - I think.

Dubbie

RE: One of My Favorite Building Blocks

michaelkellett — Sun, 16 Feb 2020 16:33:56 GMT

I'm working on some power supply designs at the moment so I was interested to see this.

I can see a problem with this design:

U3 and U2 are powered from +31V and -5.1V - a total of 36.1V, for chips with an absolute max of +/- 18V this is a potential problem because you have no margin at all for any unexpected mains blips.

Obviously quite a lot of TL081s will cope with 36.1V, but reliability will be sadly compromised if the voltage goes much higher.

I would normally design anything mains powered to be OK with worst case based on component and mains specs + 10% (because out of spec surges of 10% on mains are not unusual).

Thanks for posting and your work in tracing it out.

RE: One of My Favorite Building Blocks

genebren — Sun, 16 Feb 2020 15:49:00 GMT

Very interesting bunch of experiments around this board. I really like your approach to experiments. Well done!