- Wed Jun 07, 2006 10:36 pm
#14324
I skipped class today, but it was totally worth it.
The idea here is that a computer's power supply unit gives you 12V, 5V, and 3.3V with plenty of Amps. There is also -12V and -3V but I didn't bother with them. Anyhow, those 3 voltages as you guys know are the most commonly used voltages when you are dealing with electronics projects etc. The selectable transformer I was using was just a pain in the butt, and it could only do one Voltage level at a time so I had to clutter my bread board with regulators and extra wires etc.
The PC power supply unit gave me the multiple simultanious voltages at 10 to 15 Amps, instead of just .3 Amps. Also, PSU have a 5Vsb or stand by lead (its purple) that gives 5 volts even when the PSU isn't running. So I could have 5 volts (up to 2 amps) of dead quiet power and if I need more, I just flick the switch. The fan on this PSU is heat controlled so it generally runs very very quiet unless I start drawing large amounts of power.
I was sick and tired of using this old piece of crap for all my prototyping needs. Its awkward, ugly, and it only pushes 300mA.
So I purchased a 'project box' (its just an empty black plastic box) and some binding posts from Radio Shack. I also found a nice mini ATX PSU, some old switches and LED's and other misc stuff.
I then broke out the mighty dremel tool. Today, I decided that I would avoid having to pick black plastic boogers out of my nose. Time to practice some dremel kung fu.
Here is the PSU mounted inside the box. It was a bit of work to get it all to fit nicely and have all the holes match up etc. The fan protrudes from the top of the casing so I'd have to make a hole in the cover too.
Here is the cover with the fan hole dremeled out. I also put one standard PC power wire bundle hanging out the side (with a nice fancy grommet), this was for projects where I needed a standard molex connector for PC devices etc.
Two switches and two LED's added.
The top switch powers on the PSU. You do this by connecting the green wire on the bundle of wires that normally connect to the motherboard to ground.
The second switch just breaks the 5Vsb line leading to the binding post. Just for convienence.
The top (red) LED indicates that the PSU is plugged into the wall and is ready to go. Of this light goes dead, you are either unplugged or you blew the fuse and have to reset the PSU by unplugging it for a while.
I used 5Vsb through a 220Ohm resistor to power this LED.
The bottom (green) LED is lit up when the PSU is running.
I used the grey "Power Good" line line through a 220 Ohm resistor for this LED.
Here is everything soldered together, I just soldered the resistors inline with the LED's so I didn't have to make a circuit board or anything. Lots of heatshrink was used to avoid disasters.
Here are the binding post connections on the bottom of the cover.
And here she is all put together. The lights worked, and all the voltages checked out on the first go. I did snap two of the binding posts when I tightened them too hard, but I had an extra and I fudged the other one. I put a drop of super glue on the bottom side of each post to keep it from coming loose when I screw and unscrew them.
I color coded the binding posts to match the wiring of the PSU.
Orange for 3.3V
Red for 5V
Yellow for 12V
Black for ground (3 of them for convenience , they are common)
Hot pink for 5Vsb (its the closest to purple I had)
I then added lots of happy little color coded labels. It looked better when it was all black and manly, I know. :(
Here it is in action.
Further improvements would include:
An LED to give better visual indication on wether the 5Vsb line is switched on or not.
Normal purple instead of hot pink for 5Vsb.
Amp meters for all the voltages, probably not enough space though.
-5 and -12V posts, this power supply (or any of the mini ATX's I had) didn't have the -5V line though, its white, -12V is blue.
An ajustable Voltage regulator attached to the 12V line that outputs to its own post, for those times that you need 6V or 9V or 4.56V for whatever reason...
If anyone wants more detailed info on how to build one of your own, let me know. The cost was probably 15 dollars worth of crap, plus the power supply.
The idea here is that a computer's power supply unit gives you 12V, 5V, and 3.3V with plenty of Amps. There is also -12V and -3V but I didn't bother with them. Anyhow, those 3 voltages as you guys know are the most commonly used voltages when you are dealing with electronics projects etc. The selectable transformer I was using was just a pain in the butt, and it could only do one Voltage level at a time so I had to clutter my bread board with regulators and extra wires etc.
The PC power supply unit gave me the multiple simultanious voltages at 10 to 15 Amps, instead of just .3 Amps. Also, PSU have a 5Vsb or stand by lead (its purple) that gives 5 volts even when the PSU isn't running. So I could have 5 volts (up to 2 amps) of dead quiet power and if I need more, I just flick the switch. The fan on this PSU is heat controlled so it generally runs very very quiet unless I start drawing large amounts of power.
I was sick and tired of using this old piece of crap for all my prototyping needs. Its awkward, ugly, and it only pushes 300mA.
So I purchased a 'project box' (its just an empty black plastic box) and some binding posts from Radio Shack. I also found a nice mini ATX PSU, some old switches and LED's and other misc stuff.
I then broke out the mighty dremel tool. Today, I decided that I would avoid having to pick black plastic boogers out of my nose. Time to practice some dremel kung fu.
Here is the PSU mounted inside the box. It was a bit of work to get it all to fit nicely and have all the holes match up etc. The fan protrudes from the top of the casing so I'd have to make a hole in the cover too.
Here is the cover with the fan hole dremeled out. I also put one standard PC power wire bundle hanging out the side (with a nice fancy grommet), this was for projects where I needed a standard molex connector for PC devices etc.
Two switches and two LED's added.
The top switch powers on the PSU. You do this by connecting the green wire on the bundle of wires that normally connect to the motherboard to ground.
The second switch just breaks the 5Vsb line leading to the binding post. Just for convienence.
The top (red) LED indicates that the PSU is plugged into the wall and is ready to go. Of this light goes dead, you are either unplugged or you blew the fuse and have to reset the PSU by unplugging it for a while.
I used 5Vsb through a 220Ohm resistor to power this LED.
The bottom (green) LED is lit up when the PSU is running.
I used the grey "Power Good" line line through a 220 Ohm resistor for this LED.
Here is everything soldered together, I just soldered the resistors inline with the LED's so I didn't have to make a circuit board or anything. Lots of heatshrink was used to avoid disasters.
Here are the binding post connections on the bottom of the cover.
And here she is all put together. The lights worked, and all the voltages checked out on the first go. I did snap two of the binding posts when I tightened them too hard, but I had an extra and I fudged the other one. I put a drop of super glue on the bottom side of each post to keep it from coming loose when I screw and unscrew them.
I color coded the binding posts to match the wiring of the PSU.
Orange for 3.3V
Red for 5V
Yellow for 12V
Black for ground (3 of them for convenience , they are common)
Hot pink for 5Vsb (its the closest to purple I had)
I then added lots of happy little color coded labels. It looked better when it was all black and manly, I know. :(
Here it is in action.
Further improvements would include:
An LED to give better visual indication on wether the 5Vsb line is switched on or not.
Normal purple instead of hot pink for 5Vsb.
Amp meters for all the voltages, probably not enough space though.
-5 and -12V posts, this power supply (or any of the mini ATX's I had) didn't have the -5V line though, its white, -12V is blue.
An ajustable Voltage regulator attached to the 12V line that outputs to its own post, for those times that you need 6V or 9V or 4.56V for whatever reason...
If anyone wants more detailed info on how to build one of your own, let me know. The cost was probably 15 dollars worth of crap, plus the power supply.
I have long labored under the impression that the switchers used for PC's needed a load across at least some of their unused outputs to be stable. I guess that this notion goes back to the days when I first looked in one or two old 'true blue' IBM AT's and found some big wirewound ceramic resistors plugged into the unused power connectors for absent hard drives. I also remember seeing (not much over a year ago) an ALL Electronics advertisement for a PC type power supply that was specifically touted as not requiring load resistors when used for this purpose. Is it true that the mini ATX PSU's don't require this? Or was that back before the days of alternating current? 
