Building a Power Supply of 5,12 and 15 V DC

[ronaldiaz]

Hi, I'm new in electronics and I'm trying to build a power supply with the 7805,7812 and 7815. I would like to know how to do the electronic diagram or schematic. Is there any consideration I should know before I do it? ... I'll get 220 VAC as input and the aim is to get 5,12 and 15 VDC from different points. Thanks for your answers!

 

[MikeMl]

Have you downloaded the data sheets for the 7805,..12, and ..15?

Where ever you get your wiring diagram (and there is a lot of crap out on the Web), it is always good to check it against what the IC manufacturer recommends, viz a viz, protection diodes, bypass and filter capacitors, etc.

 

[crutschow]

You need a transformer to drop the voltage to about 15Vrms. That will give you a voltage of about 20Vdc from the rectifier filter for the regulator inputs.

You will likely need to heat sink the voltage regulators, depending upon the output current.

 

[ronaldiaz]

Let me see if I get what you mean...so I have to get a 220/15 VAC, then from the rectifier filter (which I can get 20 Vdc) I can supply three regulators (7805,7812 and 7815) without any problem?? ... or I've to use three different rectifier filters??...assuming I'm gonna use heat sinks of course! ..(sorry for my english).

 

[MikeMl]

I would use one transformer, fused in the primary winding. If the ~15V secondary does not have a center-tap, then use one 5A 100V full-wave bridge rectifier, and one big ~10,000uF 25V electrolytic filter capacitor. Wire the 7812 and 7815 as shown on the data sheets. Feed the 7805 input from the 15V output, to minimize dissipation in the 7805. Mount all three regulators on a large finned heat sink, you will need the mica washer insulating kits.

If you can find a transformer with a secondary center-tap, then everything as above, except feed the 7805 with a second large filter capacitor from the center-tap. A second rectifier is not required. That way, less heat will be produced in the 7805.

 

[Rexlan]

I'd buy a PC power supply complete with fan, case and everything else for $19 and call it a "finished project". It will laso take a 110 or 220 Vac input directly.

 

[MikeMl]

I'd buy a PC power supply complete with fan, case and everything else for $19 and call it a "finished project". It will laso take a 110 or 220 Vac input directly.

Does the computer supply output +15V?