5V Breadboard Mini PSU





Introduction: 5V Breadboard Mini PSU

About: I like microcontrollers and LEDs :D

Micro PSU to power a breadboard with 5 volts.
Connect to 9V battery, 12V or any other DC powersource from 8 to 18 volts.

Step 1: Components

To build this you need:

  • Some electronics skills. Soldering, knowing how to follow a circuit diagram etc..
  • 1 voltage regulator LM 7805
  • 1 10uF capacitor
  • 1 1000uF capacitor (you can use any big electrolyt capacitor here, doesn't have to be exactly 1000uF)
  • 1 100nF capacitor
  • 1 LED for power on indication
  • 1 resistor to to take the voltage down from 5V to whatever your LED runs at
  • 1 screw terminal for the input voltage
  • 1 switch for input voltage on/off
  • 1 perfboard, the type with copper eyes, not stripes
  • 1 2-pin connector to plug the unit into the breadboard

Resistor calculation

R = ohm of resistor
V = voltage for the LED (You can find this in the datasheet for your LED)
I = current for the LED (can also be found in the datasheet)

R = (5-V) / I
Then round up to the nearest resistor value you can find.

Step 2: Minimize

Place all the components on a perfboard to see how tiny you can make it.
I won't give any detailed instructions here, as the size and layout of the parts you use may vary from mine.

Put the components in as tight as you can, while verifying that you can in fact complete the circuit on the underside of the board without adding any wires.

When you've found your minimum size, cut out the piece you need.

Step 3: Solder

when you have figured out a way to squeeze your components together, it's time to solder.

Check the pictures to see how I did it.

Step 4: Enjoy

Plug it in your breadboard and start using



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124 Discussions

Anyone know what the ceramic cap is for? I don't have 100 pF so can I use a 500pF or 1000pF cap? Thanks

5 replies

The 100 pF capacitor reduces noise. It will work without the capacitors. But to be on the safe side, and provide a stable power source, we add capacitors. The 500pF will work just fine :)

will the 1uF work?

Hi, it that a 100pF capacitor or a 100nF capacitor? In the photo you show 100nF.

I know how all this works but can you post a schematic? I have a large breadboard and I can just plug all the stuff in a little corner somewhere

how did you solder like that? whenever i do it, the solder all clumps together onto one pad.

4 replies

 Usually when you bridge solder two joints, you ball up both pins, then get a little solder on the iron and start applying between the points. If there is enough solder on the iron or the 2 pins or all 3, then the bridge will automatically join together. But do it quickly because you do not want to burn the electronics. If it does not work the first time, add a little more solder until they join.

ok, well i figured it out anyway. thanks. i like this way of soldering, even though it uses a lot of solder.

Why don't u use staples?


i have to take soldering lessons from u seriously my soldering sucks so much. i burn half of my projects.

3 replies

Why don't u use staples?


you are most likely not using the right watt for the project you are own... sometimes it is better to use higher watt irons because they allow you to work more quickly... although your project's sensitivity will depend on the proximity to heat sensitive circuits... a good soldering station might be worth the investment so that you can play with many wattages and figure out which one is correct for the type of work you will be doing...

is it safe to skip 100nF capacitor?


Thanks for this clean, clear and small tutorial !
Although something is unclear to me, about the resistance for the led. (the most simple part of your tutorial) I understand it's depending on the Vin voltage, it's Ohm's law...


How can I choose the resistance value, if the input voltage is not fixed?

As you say input from 9V to 18V, (I guess that's the 7805 spec.)

Is there another electronic trickery I can use to prevent my led to blow up at 18V, and still be lit at around 9V ?!
(I feel stupid asking this, I lack general electronic knowledge, sorry for that)


1 reply

Xained, hes putting the led on the output so its always powered from 5V regardless of the input. Note that he placed the LED in backwards in his schematic too. Also, an LED can light up even with very large resistors and low currents. Whether you use a 220 ohm or 20kOhm it will still light up, albeit much dimmer with the 20k resistor. The key is just dont go over 20mA current through the LED.