I needed a good bench-top power supply for testing parts and gadgets.
As usual I wanted to reuse or recycle, and I could not find a suitable second-hand unit so I am making my own. Meet the PowerStation2.
So far it has cost about eight dollars, and it has more power than I need.
The guts of the system is a 200W ATX PSU from a low-profile computer workstation. It currently pushes a fairly accurate 12, 5 or 3.3 volt charge, which is what I wanted. It is rated at about 10 Amps.
So far it has four fixed channels and two adjustable channels.
There are 12V, 5V and 3.3V fixed channels, and there is also a 5V USB plug for charging devices. These channels should push 2 Amps. There is a 1.5V to 10.5V adjustable channel at 1 Amp, and a 12V to 24V adjustable channel at 5 Amps. The 1.5V to 10.5V channel can be quickly rewired as 1.5V to 22.5V if necessary to cover the range between 10.5V and 12V.
I have left several of the PC connectors that tuck into the rear compartment so I can make plug-in modules for testing things like car stereos, light bulbs and fuses, etc.
The project so far.
I had a few PC power supplies(PSUs) lying around so I decided to use the smallest of those. I shorted the correct wires to test the PSU before I went any further, as usual. It worked well as long a there was something connected to draw power. Some ATX PSUs cannot work without load. I decided that instead of wiring something in to draw power just for the sake of it, I would install something useful and I settled on a pair of fluorescent tubes from an old desktop case to provide light for my breadboard work.
I had a Playstation that could not load games so I tore that apart to use the case. I considered using the Playstation PSU to power the project instead, but I settled on the more-powerful ATX unit because it already had the power divided into three different voltages.
It was an almost perfect fit inside the case, requiring just a square cut out for the PSU fan.
I cut the green and black wires(pin 14 and 15 on the 20pin plug) and soldered them together. The power supply is now "always on". When I come across a suitable switch I will wire that in, but for now I just switch it on and off at the wall.
Next I cut a red(5v) wire and a yellow(12v) wire from the plug, as well as two black ground wires. I have seen people in the past cut and join all the wires of the same color together but I chose to use just one wire for each terminal for now because I'm not planning on drawing many amps from these channels. If I have a couple of 12V wires spare at the end I will use them for a higher-current 12V channel.
I had some old speakers ready for the rubbish so I removed the spring-loaded connectors from those and screwed them to the front of the PowerStation2. I soldered a red and black wire to the two terminals on one for a 5v connector and the yellow and black wire to the terminals on the other for a 12v connector.
Next I cut an orange (3.3V) wire and attached that to the left-hand pair of speaker-plugs on top of the unit.
I now had a power station that provided fixed 12v, 5v and 3.3V channels. Next were the adjustable channels.
5A Boost module.
This step-up/boost converter takes 12V and provides 12V to 24V at 5A. I originally bought it for my robot to boost my 12V batteries to 24V to run the motors. It didn't work well for that, producing a loud whining noise and providing no extra engine power. When I tried it on the PowerStation2, however I was really impressed with this gadget.
So far I've powered a few different laptops from 15V to 19.5V. I've also powered car headlights and a 200 watt inverter with two household lamps switched on.
For four dollars, this was the perfect way to double the voltage of my power station. Before that I was using one of the 12V wires with the PSU's -12V wire as GND. This gave me 24V, but the -12V rail is only rated at .8A, compared to the boost-module's 5A. I have routed two of the 12V wires and two GND wires to this module to allow for the current.
The boost-module outputs through the right-hand red-LED volt-meter to the banana plugs on the right-hand front of the power station.
This volt-meter is actually an old step-down regulator that no longer adjusts. It still displays voltage, so this was a good use for it.
The LM317 voltage regulator
I have written about these serial voltage regulators before so click here if you want to find out more.
Basically they use a series of resistors to produce a constant chosen output voltage regardless of the input voltage. Wired differently they can also regulate current and I will add that feature soon.
I used a 220ohm resistor for R1 and a 5k turn-pot for R2. The LM317 is fixed to a salvaged heatsink.
I used a .2uf capacitor on the input of the LM317 chip and a 1uf capacitor on the output.
The output connects through the green volt-meter to the right-hand pair of spring plugs on the top of the unit.
The little voltmeter has three wires, one for power, one GND and one measure. The unit can measure up to 100V, but the maximum voltage for powering the LCD is 30V. I connected the power to one of the 3.3V wires and the measure and GND wires to the output of the regulator. Powering the volt-meter separately means it will still work if you are using the regulator at 1.5V. It works really well considering I only paid $1.30 on ebay. I would share a link but the seller no longer has the product. I wish I had bought a few more.
I reclaimed a USB port from an old printer and attached that behind an existing opening in the front of the case.
The (almost) finished product
I love this power station. I've been using it in every day for months now, and it is rock-solid.
It looks really geeky with half of the components outside, and the PS2 case is a real talking-point with visitors.
Next I will add variable-current regulators to the adjustable channels, along with some amp-meters. Then I will start the next power station (I know, it never ends). The next unit is a Raspberry Pi and Arduino-based model with higher voltage and a poor-man's oscilloscope. It will feature a 7in display, digital voltage and current adjustment and full logging capabilities.