Mains to -12 +12 Power Supply ( Was -> PSU - Strip To Schematic )

DIY STUFF
21

Yeah, I put the transformer to one side to test at a later date.

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22

Still workign out how to do this github thing, Manually uploaded the gerbers

https://github.com/twinturbo/KOSMOPSU/blob/main/PCB2.zip

23

I’ve looked for a 110V version of that transformer with no luck. Anyone have a link?

24

It’s out there, I know it is as I found it once…

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Myrra 44452

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Thanks… Can’t find any vendors though. Newark for instance has a ton of the 230V ones but no 110V. Or 117V or whatever they want to call it.

27

I haven’t seen it.

-Fumu / Esopus

28

I think the STANDARD is “EI60-21 22VA” across various manufacturers not checked the exact dimensions on data sheets though.

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29

Hi. I have built this one and so far it works great. Here is link to my project https://easyeda.com/user.ledger/12v-500ma-ish
5V output and the LED is optional.

1410×906 111 KB

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30

Would it be safe to purchase from suppliers which have to special order from the manufacturer? I see these three:

I’m required to buy a minimum of 8 at an average cost per of €6.60.

-Fumu / Esopus

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31

there are numerous versions of a low volt ac design, I wanted to dispense with the wall wart so this uses a dual rail transformer. the required smoothing is much less and overall the cost is reduced.

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32

I will fire up the schematic and PCB later, then you can adapt it in KICAD to any footprint.

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34

The 78L05 in this schematic is fed 12 Volts and thus has to dissipate 7 Volts times the current drawn by the 5 V consuming circuit. It does not require a lot of current to heat up the 78L05 quite a bit. In similar supplies I prefer to use an 7805 in stead of 78L05 because it can stand more heat, can be mounted to a heat sink or to a metal enclosure and often times space is not an issue on the board. Furthermore it is easy to get a 7805 from a scrap circuit board you have lying around while 78L05s are more rare in that sense. This 7805 still has to dissipate the 7 Volts (times the current), so in a supply I recently build I put a DC down converter between the 7812 and set this to reduce the voltage to 8 Volts (the minimum input of the 7805), and then used a 7805 connected to the DC down converter to make a stable 5 Volt supply. In that case the 7805 only has to deal with the 3 Volts difference. The DC down converter is very efficient and does not produce much heat under load, neither does the 7805 in this approach as it only has to deal with the 3 Volts difference. The reason I do not use a sole DC down converter to render the 12 V into 5 V is because of the noise the converter makes (which the 7805 gets rid off). This may seem an expensive solution but it is not as DC down converters are dirt cheap.

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35

Just saw this…FWIW that power supply is from a photographic enlarger. Fairly nice enlarger too…I still have one stashed away if I ever get room to setup another darkroom :smiley:

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36

Ahh cool, for some reason I always like to know the origin of something. It probably came in a box of dark room stuff from the auction room.

Thanks…

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37

I mentioned that it’s a “stabilised mains supply system” for a Durst enlarger back in September, but ok… :smiley:

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38

looking back, you did, but I had not linked it to a photo Enlarger…

Why do they need such a meaty supply!!

39

Just replaced similar cap on a kenwood mixer yesterday, sadly did not fix its fault…

40

I honestly have never put 5V in this schematic. I copied it from the online sources and just used 12V version. But everything you pointed out makes sense.