9v to 5v DC Converter Circuit//Simple Circuit

Often times, I need a 5V power supply for my projects, I can take the easy path, buy one from eBay for about a dollar... or I can make a module myself that I can plug into my breadboard to power my (usually ) ATTiny85 projects.

There aren't many parts that are required... a power regulator (LM7805) chip, a couple of 100nF capacitors, some pin headers, a 220 ohm resistor and an LED indicator... that's pretty much it. Oh, a bit of FR4 copper clad board.

This circuit simply takes voltage from the left and passes it out through the middle pin of the chip as 5V. The excess voltage is spent as heat. In this circuit, I'm intending to supply 9V, so I don't need a heat sink for it. If I was supplying more than 9V, a heat sink would be wise.

I've made a bunch of these, I'm currently up to version 3 of the design and I'm planning to expand it slightly in the future (to include a toggle switch).

Fritzing ships with a Power Regulator example design, I started here and modified the breadboard and PCB layers according to my design requirements.

I started out with a very simple design that had a pair of pin headers for input and a pair for output. That's the above design.

This was good, but I could improve it.

My first improvement (v2) to the design added a second set of output pin headers. The main reason for this was to improve the mechanical connection to the board. Two pins was a bit wobbly. I also oriented the output pins downward so that the circuit could plug in directly without having to go via a Dupont Female to Male connector.

The second improvement (V3) to the design was to include a resistor and LED to indicate power.

The Fritzing design above, is the circuit PCB layout that I have come up with.

Using whatever etching technique that you prefer, etch the circuit and test it.

I've taken to using thick traces to improve the circuit etc results. They could just as easily be thin... it's just preference.

When populating your board. I start with the pin headers. The input pin headers are inserted normally and are soldered in at the top left of the board.

The connection pin headers are pushed all the way through the board so that the plastic pin header housing doesn't have any pin protruding. The pins are on the copper side of the board because that's how you plug the circuit to the breadboard.

After the pin headers, I solder the resistor and LED followed by the 2 x 100nF capacitors. Note the orientation of the capacitors, these are polarized electrolytic capacitors with the negative sides facing each other on the board.

The LM7805 is then soldered into its holes. I needed to increase the hole size for the Reg because the legs are wider than the other through-hole components that I've used.

If you want to make a 3.3v reg, simply replace the LM7805 with a 3.3V regulator (such as a UA78M33), everything else in the circuit is the same, remember, though, that more voltage is being dissipated, so the heat sink on the module will get hotter.

Now, you can plug the module into your breadboard and connect the power. When the circuit is powered, the LED lights up.

I thoroughly recommend testing your power supply using your multimeter. Above are the results for LM7805 and UA78M33C regs.