To build 5V DC power supply for development kit


How to build power supply to work with your embedded development kit part 1.


  1. 9V (or 12V) DC battery or AC to DC adaptor with 9V (or 12V) output.
  2. IC 7805.
  3. General purpose PCB or breadboard.
  4. Some wires and connectors.
  5. Soldering kit / equipment *
  6. 3 Leg, 2 position switch.
  7. General purpose diode.

* Warning: Soldering equipment may get very hot and can cause injuries, do it under the supervision of expert and be very careful.


To power your micro-controller development board / kit you’ll need 5V DC power supply. Household power supply “AC mains (alternating current)” will be 230 V/50 Hz or 110 V/60 Hz, these voltages are really bad for micros. Micro-controllers work with DC (direct current) power supply @ 5V. If we connect AC household power supply directly to micro-controller, it may end-up unexpected firework and result in dead micro.
This tutorial will show you how to build a 5V power supply using AC to DC adaptor. Most of the AC to DC adaptors convert AC to 12V DC or 9V DC, though it’s DC but still not suitable of micros. Follow this tutorial to get 5V DC.
Before we connect circuit and solder it, let’s do some brain work and try to get the concepts.

Voltage regulator:

                Voltage regulator is circuit used to obtain steady voltages – without ripples. The “ripples” are the unwanted traces of periodic variations (AC) in DC output of a power supply derived from AC source. Ripples are due to incomplete suppression of the alternating waveform in the power supply. We need steady 5V DC power without ripples for micros, if there are ripples in output it’ll create noise and will affect the circuit operation. You can imagine voltage regulators something like this:

Well, there are ICs that can achieve this functions for you, the most famous in this family is 7805. IC7805 can take 7 to 36 V DC as input and can produce ripple free 5V DC output voltage (with 1A of output current). Following diagram shows the circuit details

                One obvious question is “then why the hell we need capacitors for?” OK, here is answer to your question. Capacitor is a passive component that, blocs DC and allows AC to “pass through” it. If you observe the way they are connected to the 7805 voltage regulator, you’ll notice that this type of connection will ground AC passing though capacitor and block DC allowing it to reach 7805 on input side. DC is Blue and AC is Red

                Diode is one directional electrical gate that allows current to flow only in direction. We’ll use this feature of diode as reverse polarity protection to your circuit.


OK we almost done with the concepts in this part. Let’s try to get the things working. Connect your circuit, solder it as show below and enjoy. Check the 5V output with multimeter.