AC-DC Kit Instructions

AC-DC Regulator Kit Instructions

Table of Contents


Many circuits require a voltage supply that is constant and unchanging and such circuits would include radios, calculators, computers, monitors, phones, and even cars. Batteries are a good source of constant voltage but since they are usually limited in size, weight, and power capacity the mains electricity is often used. But this source of electricity is constantly changing as it is AC (alternating current), which is not suitable for DC (direct current) circuits. Therefore, an AC-DC converter is needed to convert the alternating current into a direct current! This kit will not only do this but will also regulate this converted DC source so that it outputs a smooth constant 5V which can be used to power many projects.

Power stations generate AC as opposed to DC and often require conversion to DC so that everyday devices can use it


Note – This is an educational kit and can only handle up to ±16V



How Does The AC-DC Regulator Work?

Input Rectification

The AC-DC converter consists of two stages

  • Rectification
  • 5V Linear Regulation Input Rectification

The input is rectified via D2, D3, D4 and D5. These diodes are Schottky which reduces the voltage dropped by this stage. The typical forward voltage for a Schottky is 0.3V and with two Schottky diodes in series at any one time (D3 and D2 pair or D1 and D4 pair), the typical voltage drop would be 0.6V.

If J1 (ACIN) is positive and J2 (ACIN) is negative then

  • D3 and D4 would be forward-biased
  • Current enters J1 and flows through D3
  • This current goes around the circuit (regulator, IC etc)
  • The return path (ground), goes back to the rectifier and through D4
  • The current returns to the original power source through J2

If J2 is positive and J1 is negative then

  • D2 and D5 would be forward biased
  • Current enters J2 and flows through D5
  • This current goes around the circuit (regulator, IC etc)
  • The return path (ground), goes back to the rectifier and through D2
  • The current returns to the original power source through J1

Output Regulation

While the converted AC voltage source looks like a sine wave with both positive and negative peaks the resultant DC conversion looks like lots of positive bumps shown below. This cannot be used to power circuits and requires further processing to create a solid unchanging voltage.

The first step is to convert the large DC bumps from the full wave rectifier into more consistent smaller bumps. This is done using smoothing capacitors C1 and C2 which store energy during the peaks of the DC bumps and then discharge this energy back into the circuit during the dips of the DC bumps.

But this voltage will be greater than 7V on average (since this circuit has a minimum input voltage of +- 5V), and is too large to feed into common circuits. The smoothed voltage will also be slightly bumpy which will cause issues with many circuits and so it requires regulation before it can be used. To do this we use the 7805 regulator which converts the now slightly wobbly voltage into a very smooth 5V.

Component List

ComponentPCB ReferenceQuantityLooks Like
7805 RegulatorU11
1N5817 DiodeD1, D2, D3, D4, D5, D66
100nF CapacitorC1, C42
100uF CapacitorC31
470uF CapacitorC21
Red Wire5V1
Green WireAC IN2
Black Wire0V1


Construction Tips

Electronics Construction Guide

To learn more about how to solder electronic components, download the Electronics Construction Manual free using the button below

Component Order

Solder the components in this order to keep things simple

  1. Capacitors
  2. Diodes
  3. Regulators
  4. Wires


Double-check your components BEFORE soldering!

  • MitchElectronics kits use double-sided PCBs with plated through-holes
  • This makes the PCBs extremely strong
  • It also makes desoldering very hard, so be sure components are inserted correctly

Final Thoughts

Be careful with this kit!

  • This is a low-voltage rectifier and not designed for use with the mains
  • To use this as a PSU, be sure to use a transformer to drop the voltage to between 9V and 12V