Computer Power Supply?
Moderators: Sir Nigel, Nina, pcs, 5r, phpBB2 - Administrators
Computer Power Supply?
Ok, So here is a new question. I have tons of computer power supplies sitting around, can I use one of these to power a MaxPro? I see the yellow line is +12vdc and supports up to 3 amps? I am assuming these are quite regulated seeing as they are computer supplies.
What do you think?
thanks.
-jon
What do you think?
thanks.
-jon
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.
Yes, but...
Yes, but....
12V output is very badly regulated. What you will have to do is
modify the power supply. This is done so that you open it up and
find where the regulator samples +5V and cut that line. Than
make a voltage divider to get 13.8V to +5V and attach that
sampling point to 12V output. A small potentiometer can make
your voltage variable, but make sure it stays below 15V if your
potentiometer breaks.
Another problem is the noise from the 12V ventilator, that might
be heard, if not filtered properly.
Good luck!
12V output is very badly regulated. What you will have to do is
modify the power supply. This is done so that you open it up and
find where the regulator samples +5V and cut that line. Than
make a voltage divider to get 13.8V to +5V and attach that
sampling point to 12V output. A small potentiometer can make
your voltage variable, but make sure it stays below 15V if your
potentiometer breaks.
Another problem is the noise from the 12V ventilator, that might
be heard, if not filtered properly.
Good luck!
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Thanks
Ok, thanks for the reply. However I am still very much an amateur when it comes to electronics. How would I find where the regulator samples the 5 volts and what is a voltage divider? I am sure I sound stupid asking this so if it is too complicated to explain don't bother.
Thanks again.
-jon
Thanks again.
-jon
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.
I know, and it is also dangerous
If you're an amateur, you better stay away from it!
There are lethal voltages present in the PC power supply,
even after you disconnect the mains cable.
For others: The 5V line is usually very narrow and is going from
the +5V smoothing caps at the output to a resistor divider
and towards the controlling electronics.
There are lethal voltages present in the PC power supply,
even after you disconnect the mains cable.
For others: The 5V line is usually very narrow and is going from
the +5V smoothing caps at the output to a resistor divider
and towards the controlling electronics.
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
I've tried this a couple of times, and I find that the results are not really worth the trouble - you're better off with a simple linear(transformer) based regulated PSU.
Most PC power-supply units can be very noisy, creating heaps of crackle or hum or both on your chosen frequency.
Also, most PC PSU's require a signal from the PC that the power is O.K. before the 5v and 12v lines become active. This is done via a "PG" wire(Power-Good), and some supplies happily work with this line tied low or high, or even not connected.
What all this means, is that if you take a PSU from a PC and plug in a mains cable and switch on, the supply might not want to work for you, without a load on it's output of at least a few amps.
Yet other(older) supplies are current-load sensitive, meaning that they need to be connected to a mother-board and CPU(which draw a least several amps when working), so that the supply output lines are loaded before the supply will maintain a constant voltage.
(not a matter of not being regulated, rather a matter of a certain load-current must be drawn from the unit before they work correctly - this loading is USUALLY provided by the CPU itself, as it draws a reasonable current.)
G.
Most PC power-supply units can be very noisy, creating heaps of crackle or hum or both on your chosen frequency.
Also, most PC PSU's require a signal from the PC that the power is O.K. before the 5v and 12v lines become active. This is done via a "PG" wire(Power-Good), and some supplies happily work with this line tied low or high, or even not connected.
What all this means, is that if you take a PSU from a PC and plug in a mains cable and switch on, the supply might not want to work for you, without a load on it's output of at least a few amps.
Yet other(older) supplies are current-load sensitive, meaning that they need to be connected to a mother-board and CPU(which draw a least several amps when working), so that the supply output lines are loaded before the supply will maintain a constant voltage.
(not a matter of not being regulated, rather a matter of a certain load-current must be drawn from the unit before they work correctly - this loading is USUALLY provided by the CPU itself, as it draws a reasonable current.)
G.
Not quite right
Grogster,
if you do the mod I described above, you don't need a few amps
to make it work. That's one of the points of the mod.
Besides a much better regulation.
if you do the mod I described above, you don't need a few amps
to make it work. That's one of the points of the mod.
Besides a much better regulation.
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Linear is better for low power
I agree, linear is simpler for a few amps.
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
18V is too much
If you use a linear regulator, such as those in the guides, to get the voltage down to at least 15V.
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Give it a try
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
-
- New registered user
- Posts: 15
- Joined: Wed Sep 25, 2002 1:00 am
- Location: The Criminal Enterprise Known as Dade City, Florida USA
- Contact:
Depending on where you live, get a Radio Shack or similar power supply that can supply the 3 amps on a regulated continuous basis. Switched mode power supplies are nortoriously noisy as thoe who used the first generation of PCI transmitters discovered.
Hope this helps.
Hope this helps.
"Repent! Quit your job and SLACK OFF"
J.R. Bob Dobbs
Visit: http://pascoradio.org
Listen: http://live365.com/stations/pascoradio
J.R. Bob Dobbs
Visit: http://pascoradio.org
Listen: http://live365.com/stations/pascoradio