DIY power supply

[MarkF]

Looks good.   

Two questions:
   1)  Are the two yellow posts the temperature probe inputs?
   2)  On the power switch, I believe it's backwards?  The'O' is the OFF position and the '|' is the ON position.


Edit:
Third question:
   3)  Can you tell me what the power supply model is?

[Pirateguy]

ehhh not anymore since i removed the sticker and painted it.
but i did google the model number before and couldn't find anything.

in any case no 3.3v or sense, but also no power on line, and only a power good indication line.
it is running without the resistor OR having to short anything at all.
all it needs is for power to be applied to the input and it runs.

the yellow posts are the negative outputs. the temp meter is internal only for now.
i think ill add the external temp later, but it will have it's own display.

the power switch is ST; it only has 2 terminals. i guess i have it mounted upside down

[MarkF]

I believe you have an older AT Power Supply and NOT an ATX Power Supply

   

[Pirateguy]

now that you mention it, lol yeah i guess you're right.
that pinout is an exact match.

[Pirateguy]

and now it's f#$cked.
when i turn it on the fan starts blowing like mad, and the -12v polyswitch pops.

checked out all my handiwork, no problems there.
and even with everything disconnected it still does it.

ill check for shorts on the board later, but i'm pretty sure i can mark this down to
the old psu's decrepitude.

hell, an AT psu... this thing must be from the P1/2 era...
i didn't recognize it, cuz i didn't remember them, lol.

anyway on to option 2:
using 2 sources like the HP one for fixed and variable, the breakout board i have for the
3.3 and 5v, and a 7812 for 12v.
which has me back with my original problem: the housing...

[MarkF]

Maybe tbe resistor you choose for the LED is too small and the LED shorted out? Try disconnecting it.

[Pirateguy]

oh i disconnected everything but the mains in, it still does it.

and i can't find a damn thing wrong with the pcb either.
all caps look good, no brown spots anywhere, nothing.

so screwit, i'm stripping this thing for parts and moving on.

[exe]

It seems I'm late to the party. I don't know if you still need a schematic, but here are two designs that are not too bad and can serve while you making something better. Although, honestly, designing a PSU is a hard topic, even a linear one. Me too was trapped into "best beginner's project is a DIY psu" (unless it's a pair of lm317 in serial, one for CC, another one for CV).

For DIY power supply one can take a typical "0-30V 0-3A" PSU. I mean this one: . Can be bought from China as a kit. Don't know its performance. It holds well in my lab, but I don't do much with it. Just be sure to read on the forum how to modify it be more robust, etc. It's worth derate it to 15V max and install a very beefy heatsink.

Another one is mine https://www.eevblog.com/forum/beginners/please-critique-this-linear-psu/ . Didn't test how well it switches between CC/CV modes, but step response is excellent (thanks to lt3080). It's my main workhorse so far. Not perfect, worth replacing lm334z with something else as it drifts with temperature. Output current is limited to what lt3080 can provide (1.1A).

[Wolfgang]

When I look at the picture, and when I see 90W of regulated output and this ridicuously small line transformer, storage capacitor and cooling, i would suggest
that you put all this in a flameproof environment. In case of a prolonged short circuit at full current this will not last long.

Play safe !

[exe]

Oh, god, I didn't even watch the video. Yep, don't do that. Or tune resistor values to limit maximum current. I'd say it's better to change the capacitor anyway as it looks too cheap to be good.

[MarkF]

I thought the BEST part is that the pots are so close together that you can NOT put any knobs on them. That alone turned me off.

RUN AWAY....   

[exe]

I think pots meant to be wired (that's what I did). Anyway, didn't check if the pcb is well routed (probably not).

[Jwillis]

I wouldn't want it anyway because he took all the fun out by building it.

[Atom]

soooo....i  didnt read all the 5 pages of post but please .... do not use the peter oakes psu is really unstable and gave me nightmares as beginner.... do you want a sturdy psu ...look for the hp3610 series or similar, you can find the schematics and make your own copy , now what i would reccomend is the Blackdog psu, that thing is a beast the voltage moves of a couple of millivolts at 4 amps load , you can find the post and the schematics on eevblog , than  this guy made a drive folder with all the info

https://drive.google.com/drive/folders/1iKNivHfgNfMc6xBsww707_LqQOR2TIin?usp=sharing

if you are a beginner beginner i would suggest to toy whit linear reg and simple switcher from ti . if you are ready to make the next step take a schematic and understand it, do not blindly copy it you will learn a lot as i did and if you have any problem you have an entire community to ask to. good luck

[Pirateguy]

soooo....i  didnt read all the 5 pages of post but please .... do not use the peter oakes psu is really unstable and gave me nightmares as beginner.... do you want a sturdy psu ...look for the hp3610 series or similar, you can find the schematics and make your own copy , now what i would reccomend is the Blackdog psu, that thing is a beast the voltage moves of a couple of millivolts at 4 amps load , you can find the post and the schematics on eevblog , than  this guy made a drive folder with all the info

https://drive.google.com/drive/folders/1iKNivHfgNfMc6xBsww707_LqQOR2TIin?usp=sharing

if you are a beginner beginner i would suggest to toy whit linear reg and simple switcher from ti . if you are ready to make the next step take a schematic and understand it, do not blindly copy it you will learn a lot as i did and if you have any problem you have an entire community to ask to. good luck

thanks

i have decided that power supplies are out of reach for me atm and
am just going to make a simple fixed output one with some 78 series regulators.

for a variable output i am tempted to go with one of these:
https://www.ebay.com/itm/RD-DPS3012-LCD-Constant-Voltage-Current-Step-down-Programmable-Power-Supply-S1I8/253019740400

[MarkF]

I just finished laying out a triple fixed output power supply using MC78xx and MC79xx.  I have in mind a +5V and +/-15V fixed outputs using two transformers.  That way the +5V will be independent of the +/-15V outputs.  Each output would be capable of 1A.

You could build it up to replace your AT Power Supply that died.  You would have to get the PCB made.

   

   

[Pirateguy]

I just finished laying out a triple fixed output power supply using MC78xx and MC79xx.  I have in mind a +5V and +/-15V fixed outputs using two transformers.  That way the +5V will be independent of the +/-15V outputs.  Each output would be capable of 1A.

You could build it up to replace your AT Power Supply that died.  You would have to get the PCB made.

   

   

looks simple enough, could you post the schematic?
i might try to build this on some perfboard.

[MarkF]

You can buy dual +/- linear supplies from eBay.  But, the heat sinks are so small that you could not pull much current from them. 
Example

   

I just threw the PCB together from the datasheet examples.  But here's a quick circuit:

Edit:
   The LEDs are there to provide the minimum 5mA load current for the regulators. 
   You can set them for whatever current and brightness you want (5mA <= I_LED <= 20mA).

   

[xavier60]

I knocked up a simple low power multiple rail power supply using 3 pin regulators.
 I also added a variable dual tracking regulator.
It has about 1% drift over its operating temperature range because the control transistors get heated unevenly by the series pass MOSFETs. The load transient response is fast at 20us.

[Pirateguy]

i got lucky and had some extra spending cash, so i went ahead and ordered that module.

for the fixed output one i don't have a split source i think, so ill make the 5v one in your circuit
and another one like that at 12v.
for the heatsink i think i will use the big one i took out of the AT and run a fan on it the same way.

can i use 4007 diodes and 4700uf caps instead?

[MarkF]

You have a little design work and choices to make here.

The 1N400x series diodes are rated for 1A.  While the 1N539x series are 1.5A but their forward voltage drop is greater.  You might look at a full wave bridge module instead of individual diodes. Your choice.

The capacitor choice depends on voltage drop/ripple, line frequency and current.  Here is a pretty good video on choosing the values:

https://youtu.be/CAYKno16weE

[Pirateguy]

i like to use what i have, and i don't need the rectifier part if i'm using a DC source like the HP supply, do i?
but there are 2 more diodes to the right, i was thinking of those.

in any case my poly fuses are 0.9A so i guess these will do.

[Pirateguy]

i i watched the video and followed the math, and i end up with a 10uf cap.

so i am guessing that corresponds to the 10uf cap in the circuit, but i was thinking of the 6800 one.

[MarkF]

i like to use what i have, and i don't need the rectifier part if i'm using a DC source like the HP supply, do i?
but there are 2 more diodes to the right, i was thinking of those.

in any case my poly fuses are 0.9A so i guess these will do.

The two diodes on the right side are protection diodes.  They are for reverse-voltage and over-voltage being applied to the outputs.  You want those and you could use your 1N400x series diodes there.

You're right. You don't need the rectifier if you feed a DC voltage into the regulator.  And the input capacitor can be small.  I'd use something like 100uF. 

The video is not applicable if you feed the regulators with a DC voltage.

The maximum input voltage of the MC98xx regulators is 35V.  If you intend to use your 32VDC supply to feed 5V and 12V regulators, the power dissipation of the regulators will be enormous.  They will get very very very hot!  You want an input voltage to the regulators 5-10V above their output voltage to minimize the power they will need to dissipate.  Don't forget their drop out voltage is 2V.

I DO NOT think your 32VDC power supply is an appropriate choice.  If you want to build this, I highly recommend you use the bridge rectifier and obtain the appropriate sized transformer for each.

[Pirateguy]

The maximum input voltage of the MC98xx regulators is 35V.  If you intend to use your 32VDC supply to feed 5V and 12V regulators, the power dissipation of the regulators will be enormous.  They will get very very very hot!  You want an input voltage to the regulators 5-10V above their output voltage to minimize the power they will need to dissipate.  Don't forget their drop out voltage is 2V.

I DO NOT think your 32VDC power supply is an appropriate choice.  If you want to build this, I highly recommend you use the bridge rectifier and obtain the appropriate sized transformer for each.

seriously?
after 5 pages of discussion, diagrams and shopping advice, you are basically telling me to shove a 5v and a 12v wallwart into a
box and call it a project?

if i happen to have a wallwart for every voltage i want, do i still need the regulators?