Simple Bench Power

squadMCU — Thu, 07 Oct 2021 09:45:44 GMT

Current Revision posted to Documents by squadMCU on 10/7/2021 9:45:44 AM

When dealing with electronics you need 1 key thing, electricity. For quite a while now if I needed 5 volts I would just grab my homebrew arduino, but that is not always handy and its tethered to the pc and it does not have 3v. If I wanted 3 volts, now I am digging around looking for my UBW32 which does have 3v3 but now I have a 50$ microncontroller with very small regulators (so therefore only small loads) dangling around just for power, and its a mess.

So I need just a board that takes some DC from a wall wart and regulates it to usable voltages, and I set about to make it. This regulator board puts out +5, +3.3, variable and negative variable voltages, is pretty easy to make, and make a nice addition to the bench. (until I can get a real bench supply someday)

Now I know this is not ground breaking hackery, but I hope it helps someone out there, join us after the break to see what’s going on.

First up, parts! I started by reviewing the datasheets for the 3 regulators, and pretty much throwing most of their advice away as most of this was scavenged parts. Beggars can’t be choosers.

That works mostly okay, but due to my resistance choices on the LM317T I am loosing a bit more (about an extra volt!) than I should be in the regulator. I used 100 ohms and 1khoms for the voltage adjustment … 120 and 2k or 240 and 5k would have been a much better choice, if I had those parts on hand.

But this is what I ended up using

1*SPST toggle switch

1*LED of your choice and appropriate resistor for 5 volt operation

3*Silicon rectifier diodes (I am using 1N4001′s but most would do fine)

2*47uf capacitors with voltage ratings higher than ~16 volts (I am using 50 volt caps)

1*10uf capacitor (its for the 3.3 volt line so anything more than 3v will work)

1*4.7uf capacitor (again I am using a 50 volt)

6*100nf ceramic capacitors (code 104)

2*100 ohm resistors

1*1k ohm resistor

1*1k ohm trimpot

1*7805 in a TO220 package

1*3 volt regulator in a TO220 package (I am using a ST “LD33V” though its not common)

1*LM317T in a TO220 package

1*555 timer

4*Dual terminal/ screw blocks

1*Large 3 position heatsink or 3 normal TO220 heatsinks

Wire, solder, and a 2 position jumper