My Breadboard Power Supply is designed to overcome a number of problems with other existing plug-in power supply designs. At a glance, it might not seem to make much difference how my supply board is designed compare to other solutions - they all get you a stable voltage from a wall wart - but read on for how those differences actually matter.
Most Breadboard power solutions provide a single output from a DC jack. This is fine if you know you'll only ever need one power rail. But increasingly ICs and components are only available with 3.3V, and other components don't run at their top speed unless being fed at 5V. Having both available at once is more of a necessity than it has been in the past.
For example, Microchip make one of the only Ethernet chips you can plug into a breadboard: the ENC28J60. A small, through-hole IC, which provides almost all the hardware needed to add Ethernet - just a jack, some magnetics, and terminaton is required. But this part is 3.3V only. Similarly, to get the maximum speed out of a AVR MCU you can plug into a breadboard, say the ATMEGA328P (like an Arduino uses), you need to run them at 5V.
So my breadboard supply board provides you both at once. You don't have to switch between one or the other. Both 3.3V and 5V are available from the same input and the same board.
The second problem with most supply boards is the way they connect to the breadboard. A breadboard has down each side two power rails (usually marked red for positive and blue for ground), and it's natural instinct to connect a supply board directly to these rails.
But there's problems with connecting that way. Not all breadboards have the same width. The main area of a breadboard, the grid of holes, is always spaced the same, but the number of columns varies between breadboards, and the distance from the grid to the power rails varies as well. This means most supply boards will either only connect to a single side rail or if they do try to connect to both, they are only able to connect to a few specific breadboards.
Instead, I noticed there's one area of a breadboard which is always consistent - the IC well. Breadboards are designed to accept all DIP packaged ICs, their pins are always spaced on a 0.1" grid. So all breadboards have their grid spaced the same way. And to split the sides of a chip into separate lines, they have a well down the middle. That too is spaced on the same 0.1" grid, to ensure any DIP chip will fit.
That's the better, more reliable, place to connect a supply board - it'll always be the same spacing on any breadboard. Since it's also split between sides, it makes it easy to provide both 3.3V and 5V at once - they are just different sides of the IC well.
Most supply boards droop off the end of the breadboard, which is both sloppy and may damage the breadboard or pins in the supply board. My supply board uses additional pins to provide stability, so there is no droop and the board and pins are firmly held in place without bending.
The LEDs for each side are also placed nice and close to the pins where the output is present, so you can see easily that each side is live. I've also put more emphasis on limiting the number of components down to what you really need, and not things which aren't critical to have. This means my supply board is much cheaper, about 30% cheaper than other boards with only a single output, and you get two outputs from my supply board.
It's also been designed to be easier to install a small heatsink on to the regulators. Linear regulators do generate a significant amount of heat, but most boards try to cram too many components around the regulators, making it hard to use a small heatsink to improve how much current can be drawn from the supply board.
By keeping the space either side of the regulators clear, it's very easy to glue down a small heatsink designed for DIP packages to both regulators. Very few supply boards can accept a heatsink this easily.
Lastly, buying locally means you get customisation options. The boards can be supplied with custom voltages, or without pins or DC jack loaded so you can solder it into a fixed installation.
In summary, the hairy.geek.nz breadboard power supply:
- Provides two outputs at once, instead of only one
- Prevents damage to the breadboard by limiting droop from the power input
- Fits to any breadboard
- Provides a clearer indication power is on
- Ensures you can easily install a heatsink if required
- Is lower priced than most single-output boards
- Can be customised to your specific needs
You can get the hairy.geek.nz Breadboard PSU from nicegear here.