Hello and thanks beforehand for your input.
It has become apparent after tooling around trying to teach myself circuits/electronics that I am in desperate need of a benchtop power supply. So... as my first real project, that's what I am going to do. However, I need some help from you folks so I do this right (again, very new to this stuff).
I've ripped a Dell 7000679-000 PSU out of an old poweredge server. This is rated +/-12v @ 60 Amps and 3.3v at 3 amps. Here's a pic of the pin-outs for reference:
First round of questions:
1) Sooo (dumb question forthcoming)... with all the current (simple) circuits I've built the flow goes from positive to negative. I understand (I think) that this power supply is dual rail (full wave rectified) with outputs for +12v and outputs for -12v. This seems useful for a bunch of stuff, not the least of which is testing opamps. BUT let's say I wire/solder all the +12v pins together and apply that to a circuit, how do I complete the circuit... where do I connect the end? Would I just throw it back to a ground pin (there's approx 4 of them in that little bunch of pins)?
2) Also, I would also like to make this a variable supply... is there a circuit I could build (connected to the outputs) that would allow me to do this? Could I just use a simple potentiometer on the output? If so, can you suggest one that could handle this type of voltage/amperage (that's potentially almost 30amps per 12v rail)? I've not found anything close to that... for instance the maximum watt handling I found at jameco was 10.
It has become apparent after tooling around trying to teach myself circuits/electronics that I am in desperate need of a benchtop power supply. So... as my first real project, that's what I am going to do. However, I need some help from you folks so I do this right (again, very new to this stuff).
I've ripped a Dell 7000679-000 PSU out of an old poweredge server. This is rated +/-12v @ 60 Amps and 3.3v at 3 amps. Here's a pic of the pin-outs for reference:
First round of questions:
1) Sooo (dumb question forthcoming)... with all the current (simple) circuits I've built the flow goes from positive to negative. I understand (I think) that this power supply is dual rail (full wave rectified) with outputs for +12v and outputs for -12v. This seems useful for a bunch of stuff, not the least of which is testing opamps. BUT let's say I wire/solder all the +12v pins together and apply that to a circuit, how do I complete the circuit... where do I connect the end? Would I just throw it back to a ground pin (there's approx 4 of them in that little bunch of pins)?
2) Also, I would also like to make this a variable supply... is there a circuit I could build (connected to the outputs) that would allow me to do this? Could I just use a simple potentiometer on the output? If so, can you suggest one that could handle this type of voltage/amperage (that's potentially almost 30amps per 12v rail)? I've not found anything close to that... for instance the maximum watt handling I found at jameco was 10.
The issue with server supplies is getting the information needed to jumper the right terminals to get it to work. Info is available on a few units, but I have a pile of these that are just promising boat anchors since Dell will not supply the appropriate information.
Well... as shown above, I've got some good info already. Can power on and off, etc. I've found some very useful threads over at the RC forums but, frankly, these folks are generally only using one rail to charge up their stuff.
If it's helpful to you, then here's the pin-out map they've figured out on these Dell PSUs:
Also, here's a general PDF on the pinouts of some different server PSUs (IBM, HP, and Dell): https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CEUQFjAC&url=http%3A%2F%2Fkrcm.mywebnow.org%2Findex.php%3Faction%3Ddlattach%3Btopic%3D264.0%3Battach%3D1365&ei=EM1nUvOSFrf84APb4oGwAg&usg=AFQjCNECps9m5lk6FXqpoDF1QJHfehaYKw&sig2=euLSBWr71Pa9wk6u6fEQzw
So... my issue isn't so much is the device usable. It is. I just lack the knowledge necessary to use it most effectively. Can you answer my more general electronic questions from above?
If it's helpful to you, then here's the pin-out map they've figured out on these Dell PSUs:
Also, here's a general PDF on the pinouts of some different server PSUs (IBM, HP, and Dell): https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CEUQFjAC&url=http%3A%2F%2Fkrcm.mywebnow.org%2Findex.php%3Faction%3Ddlattach%3Btopic%3D264.0%3Battach%3D1365&ei=EM1nUvOSFrf84APb4oGwAg&usg=AFQjCNECps9m5lk6FXqpoDF1QJHfehaYKw&sig2=euLSBWr71Pa9wk6u6fEQzw
So... my issue isn't so much is the device usable. It is. I just lack the knowledge necessary to use it most effectively. Can you answer my more general electronic questions from above?
You're lucky, I've looked there before and they have zero information about the supplies that I have.
In any case:
1. The positive and negative supplies are likely independent, not full wave rectified. That's irrelevant for what you want to do, but I thought I should mention that.
2. The voltages are given with respect to the power supply ground. So you could use just the +12, or just the -12, or both, since they will have a common ground reference.
3. The multiple outputs will either be independent (in which case you shouldn't parallel them) or internally tied together (in which case you don't need to parallel them).
In any case:
1. The positive and negative supplies are likely independent, not full wave rectified. That's irrelevant for what you want to do, but I thought I should mention that.
2. The voltages are given with respect to the power supply ground. So you could use just the +12, or just the -12, or both, since they will have a common ground reference.
3. The multiple outputs will either be independent (in which case you shouldn't parallel them) or internally tied together (in which case you don't need to parallel them).
Alright, now we're getting somewhere.
1) "The positive and negative supplies are likely independent, not full wave rectified. That's irrelevant for what you want to do, but I thought I should mention that."
Thank you... being a beginner, learning this type of stuff is important.
2) I'm not sure I understand. Let's say I just use the +12v and apply that to a circuit. How do I end the circuit; where do I tie it back to so that electricity will flow... I know this is prob. a dumb question but, like I said, all the circuits I've built thus far have a positive and negative side (like on a battery)... but here I've just got the +12v. Where does it go?!
3) In that PDF mentioned above, the author states, "There are 6 power pins to the right of the small pins. The three left pins are the -12V and the three right are +12V. These terminals must be paralleled to be able to handle full load rating of the power supply". That seems contrary to your statement - can you please expand upon this?
4) Can you answer my other question from above about making this a variable supply... is there a potentiometer that can handle this type of current? Should I instead build a voltage regulator circuit? Or, something else?
And, lastly, in that PDF, the author also states, "In order to isolate the chassis from -12V the supply must be opened and three screws removed and isolated with fibre or nylon washers under the PCB and under the screw head." Why, exactly, would I want to do this?
1) "The positive and negative supplies are likely independent, not full wave rectified. That's irrelevant for what you want to do, but I thought I should mention that."
Thank you... being a beginner, learning this type of stuff is important.
2) I'm not sure I understand. Let's say I just use the +12v and apply that to a circuit. How do I end the circuit; where do I tie it back to so that electricity will flow... I know this is prob. a dumb question but, like I said, all the circuits I've built thus far have a positive and negative side (like on a battery)... but here I've just got the +12v. Where does it go?!
3) In that PDF mentioned above, the author states, "There are 6 power pins to the right of the small pins. The three left pins are the -12V and the three right are +12V. These terminals must be paralleled to be able to handle full load rating of the power supply". That seems contrary to your statement - can you please expand upon this?
4) Can you answer my other question from above about making this a variable supply... is there a potentiometer that can handle this type of current? Should I instead build a voltage regulator circuit? Or, something else?
And, lastly, in that PDF, the author also states, "In order to isolate the chassis from -12V the supply must be opened and three screws removed and isolated with fibre or nylon washers under the PCB and under the screw head." Why, exactly, would I want to do this?
A variable supply is a different beast. Yes, you could do it with a regulator following the output. It would be cheaper to buy a variable supply! 😀
If the outputs are designed for paralleling and you need the full load current, then follow the recommendations. For opamp circuits, you won't be even close to the max ratings.
Return is to ground, i.e., the +12 flows to ground, the -12 flows to ground. In a bipolar circuit (like most opamps), you'll have three leads, a positive, a negative, and a ground.
If the outputs are designed for paralleling and you need the full load current, then follow the recommendations. For opamp circuits, you won't be even close to the max ratings.
Return is to ground, i.e., the +12 flows to ground, the -12 flows to ground. In a bipolar circuit (like most opamps), you'll have three leads, a positive, a negative, and a ground.
To make the +- 12 V outputs variable see here http://www.ti.com/lit/ds/symlink/lm137.pdf These parts will do what you want up to some current. The examples can be taken from the data sheet pretty much as is. You should also be thinking about some type of current meter for each supply. Invaluable for a lab supply. Have you got this supply running and putting out juice? Some PC switching supplies require a bit of a load before they will turn on. Also this approach is not the best. I know that it is easy but try looking into linear power supplies for the bench. Food for thought.
Since 99% of the solid state stuff I fool with works fine at +/-12V, I use a computer supply as a fixed source. If I could get my server supplies fired up, they'd be running tube heaters...
Thanks SY for your time today! If you don't mind, just a couple follow-ups...
You say it would be cheaper to buy a variable supply but how about this example:
I can't even imagine using all that current so rather than wire the outputs in parallel, say I just take a single +12v output which (it seems to me) would put out no more than 10amps and added a voltage reg circuit using Jameco - variable voltage regulator 10amp max - $5.79? Seems like that would work and cost less than $10. Thoughts?
Lastly, I just want to be VERY clear about this, you say both the +12v and the -12v flow to ground. Are we talking a common ground on the chassis?
Thanks for your reply too Firechief (I missed it the last time I posted). Yes, I've got this fired up. Re: current meters, would you mind suggesting a couple? My searches are returning lots of water based current meters 😕. Also, these power supplies are very well regulated (albeit switching) can you help me understand the benefits of a linear supply for the bench?
You say it would be cheaper to buy a variable supply but how about this example:
I can't even imagine using all that current so rather than wire the outputs in parallel, say I just take a single +12v output which (it seems to me) would put out no more than 10amps and added a voltage reg circuit using Jameco - variable voltage regulator 10amp max - $5.79? Seems like that would work and cost less than $10. Thoughts?
Lastly, I just want to be VERY clear about this, you say both the +12v and the -12v flow to ground. Are we talking a common ground on the chassis?
Thanks for your reply too Firechief (I missed it the last time I posted). Yes, I've got this fired up. Re: current meters, would you mind suggesting a couple? My searches are returning lots of water based current meters 😕. Also, these power supplies are very well regulated (albeit switching) can you help me understand the benefits of a linear supply for the bench?
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The ground may or may not be connected to the chassis. Use the supplied ground connection as the power return.
Why do you need 10 amps?
Why do you need 10 amps?
The chip you linked to is a fixed output, and only one component of the regulator circuit. You could probably design something for variable output, but by the time you pay for all the support circuitry, pass transistors, pots, case, meters, et al, you could get a fully functional variable supply off EBay.
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