ATX Bench Power Supply

Inspired by another post, I decided it was time to create my own bench power supply.  A good bench power supply is something that can be really handy to a burgeoning electronics enthusiast.  It makes it much easier to prototype quickly because you don't have to first figure out the power circuit before getting to what you are actually excited about tinkering with.

This is a fairly simple project.  It is mostly just re-routing wires from one place to another.  The main component is an ATX power supply, which can be found in almost any desktop tower computer.  Besides that I just needed to order an appropriate switch and some banana plug binding posts.

Desktop power supplies can range greatly in total power output, but for hobby electronics the most basic 150-250 watt power supplies are way more than enough power for most projects.  What makes an ATX power supply ideal for this, is that it outputs 4 different standard voltages (5V, 3.3V, 12V, -12V), and it is already designed for microelectronics, so the output is very steady with a minimum of noise.

Power supply from my old Dell desktop

I recently retired an old computer so I had a power supply on hand to get started.  First thing I did was take off the cover and have a look.  Next I tested that grounding the green wire would start it up.  It did, so I got to work installing the the toggle switch to act as a power switch for the unit.

Drilled hole in the back for the switch.
The smaller hole on the bottom is for a little tab on the washer that
keeps the switch oriented in the right direction

The switch installed

At this point I thought I was on my way to finishing this project, but I hit a major snag.  I had stripped the ends of a few of the wires to test what their outputs were.  I believe the "always on" 5V wire (purple) shorted to ground.  I saw a flash and heard a loud pop, and the power supply no longer worked.  Bummer.

So I needed to find another power supply to finish the project.  Luckily my uncle had an old computer hanging around that he was willing to donate to my cause.  So I was back in business. This power supply was much more compact, and I wasn't going to have much room to work, but I thought I could make it work.

Not much room to work...

So I pulled off the switch an moved it over to the new power supply.  Next I figured out where I was going to place the posts and got to drilling the holes.  Here is where I hit another snag.  I needed to drill the holes out to 3/8" to install the posts properly.  What I found was that hand drilling a hole that size in soft steel doesn't work to great.  I ended up completely tearing up and warping the power supply case.  It wasn't going to work.

Ruined case.  Looks like it was in a gun fight...

Now I had two busted power supplies.  One with dead inards and another with a ruined casing.  So now my only option was to take the guts out of the new one and put it in the old case.  This worked out ok.  two of the pcb mounting holes even lined up.  And now I had more room to mount the posts.  The only modification I had to make was clipping the main power lines and joining them back together after mounting the guts.

Guts from viable power supply

Case from first power supply

My second try at drilling the holes was much more successful.  A sturdy backing to drill against made a big difference, but it was still touch and go.  After that I was able to start mounting the posts.  I chose these colors because they match the wiring of the power supply.  Red = 5V, Orange = 3.3V, Yellow = 12V, Blue = -12V

Mounted Binding posts, back

Mounted Binding posts, front

Wiring the binding posts was just a matter of collecting all the like colored wires and soldering them to the correct post.  I split the ground (black) wires in half between two posts.  But I did connect the two posts with a couple joining wires so all the ground wires could help share the load.

This power supply also had a wiring for an LED that would be lit when the power cord is connected.  I think is serves a second purpose of bleeding the capacitors when the power cord is disconnected, so I made sure to keep it in the design, although I had to extend its wires to get it to the front panel.  I also added a blue LED as a power indicator when the unit was turned on and ready for use.  I just wired the LED with a resistor directly to the red and black posts from the inside.

Wiring complete

Wiring complete, back

One of the hardest parts was cramming all the wires in the unit as I was trying to close the case.  It took a couple tries to get everything to fit in properly but I got it all in there.

Finished (except the leds popped out, had to bust out the super-glue to remedy that situation)

Power supply off

Power supply in action

In conclusion, I'm very happy with the project.  I was able to re-purpose some old equipment into a very useful tool that I can hopefully get many years use out of.

Home Carbonation

Just installed a home carbonation system.  My wife and I love drinking fizzy water, but were feeling eco-guilty about all the plastic bottles we were going through on a daily basis.  So we decided to take the plunge and just do it ourselves at home.

I got the inspiration from other posts I found on the web about how easy this is and how economical it becomes after the initial set up.  The carbonated water is pennies per liter once the setup is operational.

Here is a great instructable for a more DIY solution, which was my main inspiration.  At first, I thought I would go this route myself.  But after visiting the fine folks at Bob's Homebrew Supply, I decided that I was fine with them doing all the hard work.  So we ended up buying their off the shelf keg carbonating system, with an adapter for standard pop bottles.

10lb CO2 tank

CO2 line with standard keg coupler and Carbonator bottle adapter

Dual gauge pressure regulator

After picking up these items, the only other things we needed were a big wrench and some Teflon tape to get the seals tight.  The bonus with using this standardized system is that we are ready to pressurize a keg of beer at a moments notice.  Some home brewing is definitely a possibility in the future.

After connecting all the pieces, I set the regulator to output at 25psi, and in a matter of seconds, carbonated my first bottle of water.

Heather enjoying her fist glass of home carbonated water

Tank in its permanent home under the sink

Now it is just a matter of keeping cold water in the fridge ready to be carbonated on demand. We are also excited to experiment by adding our own flavors to the water and also carbonating other drinks.

Car Stereo Aux Input Hack

After seeing a similar hack posted on hackaday I decided to give this hack a shot myself.  I bought my stereo back in 2001 before auxiliary in ports were mainstream in car stereos.  But in the last few years I've really wished I had one, but didn't really feel like upgrading a stereo in a 14 year old car.  So I was very excited when I found out there might be another option.

My stereo is an Alpine CDE-7859.  My goal was to figure out a way to bypass the fm tuner output and patch in the signal coming out of a stereo jack.  Using the example from the other post, this wasn't too hard.

For my first attempt I used a similar setup with the stereo jack that contained its own cut off switch.

First thing was getting the stereo out of the car.  Then dismantling the stereo to get at the circuit board.  The hardest part about this was taking off the cd player.  But the stereo itself was pretty easy to take apart.  I didn't take a picture of it, but locating the the FM module was pretty easy to find.  It was a seperate module wrapped in metal just Mukmuk found during his tear down.  But looking where the FM module was connected I found pins marked L, R, and Gnd.  So I was in business.

On my stereo the capacitors were surface mount, so I had a little less room to work with.  So next I used a Xacto knife to break the circuit between the pins and their capacitors.  And then with the help of my lovely wife I was able to squeeze in the four wires I needed to make my new circuit.  And the ground wire was off to the side so it was easy enough.

After that it was simple enough to wire up the the switch.

Only problem was that I forgot that I still needed to feed this thing through a hole.  Oops, I'm still new at this stuff.  So I had to take it off.  And then I put the stereo back together with the wires in place on the board.  Everything still fit fine.  There was even a perfect slot in the back of the stereo for the wires to come through.

I couldn't just put a hole in the front of my stereo for the Aux since my stereo has a removable face plate.  After installing the stereo back in the car it worked great, but after using it a while I decided that I wanted to change the design.  I wasn't happy with the aux jack being the functionality switch.  I decided I would rather just have a dedicated switch somewhere on the console to turn the Aux on and off.  And then I could just leave a cord semi-permanently attached to the jack.

So I ordered a switch I thought would work.  The hardest part was figuring out where it would fit on the console.  But I made it work.

After putting the console back together I wired it all back up.  It was pretty easy the second time.

And here is the hack in action.