My first ever simple breadboard PSU

[antolanca]

Hello EEVBlog.

Gonna build my first ever dual voltage PSU but would like your opinions on it.

On paper and simulated in Yenka it works. But in your more experienced view will it work?

Thanks in advance for any help.

[Ian.M]

Totally useless.  The '5V' setting will output around 3.5V and the '3.3V' setting will output around 2.5V, sagging approximately 1V for every 3mA of load current!

If you are starting from a 5V USB charger, then all you need for the 5V setting is a 200mA polyfuse to provide over-current protection.  The 3.3V output needs a LDO regulator with decoupling caps as specified in its data sheet.  Use a SPDT center off switch at the OUTPUT to select the voltage 5V from before or 3.3V after the LDO regulator.

Also indicator LEDs go across the supply, with a current limiting resistor in series with the LED, *NOT* in series with the output!

[ZeTeX]

Get an adjustable low dropout linear regulator and be done with it - cheap, easy, and reliable and also adjustable voltage.

[Alex Eisenhut]

http://www.ebay.com/itm/Continuously-Adjustable-Regulated-DC-Power-Supply-DIY-Kit-LM317-1-25-12V-US-V7M2-/131743251138?hash=item1eac827ac2:g:4nEAAOSwwpdW2QAb

 

[dannyf]

On paper and simulated in Yenka it works. But in your more experienced view will it work?

If you are to use it to power very low load (a few ua for the lower one and a few ma for the upper one), it can be of some use.

Try to get a 3-terminal regulator and you can pretty much wire it up on the breadboard itself. Much simpler and far more useful than what you have here.