ATX Power Kit
|ATX Power Kit|
|Start Date: 02/05/2010|
|End Date: 08/31/2011|
Expanding on the ATX Power Panel that Paul created, we want to create a simple kit that would allow others to build a similar device.
Designed a box that plugs straight into a 20/24-pin atx power connector. Has 4 grounds and 3.3, 5.0, 12, and -12 volt binding posts. Schematics, BOM, etc (and kits available for purchase!) are here: http://www.gfxhax.com/cart/index.php?main_page=product_info&cPath=2_8&products_id=7
- James is going to design the board layout, which we will print on the laser printer, iron on and acid etch this round. He will be doing this at our Feb 16 meeting as an introductory review of the EAGLE Layout Editor.
- We need to have someone that has access to metal stamping to create a L-Bracket for mounting the power supply to the base. The idea is the user supplies a 1x6" board and mounts the ATX bracket and the circuit to the board. Screw the power supply to the bracket, plug it in and you're ready to go.
WARNING: Opening up a power supply can be extremely dangerous if you do not know what you are doing. I take no responsibility for any actions that result from you following this guide. Do NOT turn on a power supply while it is open as this charges the capacitors in a power supply, which are rather large.
After seeing Paul's atx power supply kit at the space I decided it would be really nice to have one. I had a power supply, but it was broken. Thankfully there is a big box of old atx power supplies at the hive so Paul helped me find a working one. Once I had the power supply it was extremely an extremely straightforward process to turn it into a power kit. Instead of mounting the power supply on a board and mounting binding posts on the board I though it would be nicer if I could simply mount the binding posts directly on the case. Make sure that the binding posts have an insulating collar on the screw so it does not end up touching the case and getting grounded. Paul said he had some issues with this using the binding posts he had.
I made sure there were a few wires I didn't cut besides the ones going to the binding posts. The 3.3v sense wire, so if the voltage on any of the rails went too far off the power kit shuts down, and an extra +3.3v for an led to tell if the rails are powered. The only issue with the sense wire is that you can only go from one binding post to ground. You can't go from a +12v post to a +5v post or the +12 to a -12v. If you want to enable the 3.3v sense wire, then solder it directly to another 3.3v wire. If you don't want it, or you have soldered it and want to get rid of it then just cut it and leave it alone.
Before I started cutting away I sat down and thought for a minute on which binding posts I wanted. If you are going to mount them externally then you don't really have to worry about this and you can have whichever binding posts you want. I also made sure that when I was cutting away I still left about an inch of wire on each one just in case I wanted to rewire them. I ended going up with one of each: +3.3v, +5v, and +12v and two grounds. Leave the wires you wish to keep at their full length for now. For me this was two +3.3v lines (one for an led), one +5v line, one +12v line, and 3 ground wires (again one extra for an led). At this point I cut the wires down to about an inch of the circuit board. Before you choose where you want your binding posts and start drilling look in your power supply and measure where the best place to mount the binding posts would be. Remember that they generally stick out anywhere from .5in to 1in! The fan in my psu got in the way of one of my binding posts making it bow out a teeny amount and making it more difficult to take the case off and put it on. Stupid mistake on my part.
Once you have done that drill the holes for your binding post and a hole for the led that is in a visible spot. Mine is on the left of my binding posts so you can see it's on at a quick glance. Once you have all of your holes drilled, measure to see how far the wires need to stretch the wires so they can easily be attached to the binding posts. Remember that there needs to be extra slack to remove the case if you ever need to! Make sure you give yourself an extra inch or two of wire just in case. Don't leave too much extra wire, as it all has to cram in to the case of the psu! I wired my led up with a 1/4 resistor and chose a resistance so about 10-15mA of current is going through it. Even though heat should not be an issue, because the led will be touching the case and the fans in psu move quite a bit of air, I still chose a lower amount of current because the led is still fairly bright and I don't want to over stress it and reduce its life time. NOTE: Do NOT turn on the power supply to test the brightness of the led. The components in a power supply are extremely dangerous if on, or even charged from being turned on. Once I had the led wired up I taped up it's lead to insulate them and then taped it through the hole I drilled in the case.
Once you have everything mounted you can screw the case back together and turn it on! If all went well you should see the led turn on and be able to measure the voltage of each binding posts. I went ahead and labeled what amperage each rail could supply, just in case I needed to know. Your binding posts may be a little bit off. They should be within ±5% of the stated voltage. Even if they are a little bit off the power supply is extremely nice because the voltages are extremely stable and there are many, many safety fall backs to prevent a lot of bad things from happening.
Instead of going with a PCB for the ATX Kit I opted instead to wire everything together. This allows people to use it as a high power kit. With a pcb anything above an amp or two requires very large traces so that was not a very viable option. I have pictures and information (schematics, file for lasercutting the enclosure, BOM, etc) up at the product page for the kit: http://www.gfxhax.com/cart/index.php?main_page=product_info&cPath=2_8&products_id=7 .