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ATX power supply to drive a 12V DC motor?

M

MK

Hi,

I have a 12V DC motor (6A under load). The only power supplies I have
around here are ATX. Someone at an electronics shop told me they can be
used to supply the power, but I didn't ask how. Is it just a matter of
using an IDE connector to power the motor?

Regards,

Michael
 
E

Eeyore

MK said:
Hi,

I have a 12V DC motor (6A under load). The only power supplies I have
around here are ATX. Someone at an electronics shop told me they can be
used to supply the power, but I didn't ask how. Is it just a matter of
using an IDE connector to power the motor?

You don't mean an 'IDE connector', that's the ribbong cable. You need the 4 way
Molex power connector.

You're almost certainly going to need to put some load on the 5V supply too or
the PSU probably won't function properly.

Graham
 
B

BobG

Eeyore said:
You're almost certainly going to need to put some load on the 5V supply too or
the PSU probably won't function properly.
=======================================
Yo Eeyore... isnt it tricky to get an ATX ps to turn on? The old xt and
at supplies seemed to always turn on... whats the trick with the ATX is
its not connected to a MB?
 
E

Eeyore

BobG said:
=======================================
Yo Eeyore... isnt it tricky to get an ATX ps to turn on? The old xt and
at supplies seemed to always turn on... whats the trick with the ATX is
its not connected to a MB?

You need a momentary switch don't you ? Google it. There's stuff out there to tell
you where it needs to go.

Some ATX supplies still have a rocker switch on the back though.

Graham
 
A

Arlet

BobG said:
=======================================
Yo Eeyore... isnt it tricky to get an ATX ps to turn on? The old xt and
at supplies seemed to always turn on... whats the trick with the ATX is
its not connected to a MB?

On the big connector that goes to the motherboard there's a green wire
(4th one from left, with the retaining clip facing you). Connect the
green wire to ground (black wire) to turn it on.
 
V

vic

BobG said:
=======================================
Yo Eeyore... isnt it tricky to get an ATX ps to turn on? The old xt and
at supplies seemed to always turn on... whats the trick with the ATX is
its not connected to a MB?

Actually it's easy, you just need to ground the /PS_ON signal (pin 14,
usually a green wire).

vic.
 
M

MK

Hi Graham,

Ok, thanks for pointing that out. Is the 4 way connector you referred
to the 12V power connector (with 2 black, 2 yellow wires)? If so, is it
just a matter of connecting a yellow and black wire to the motor?

Also, which is the 5V supply? Correct me if I'm wrong, but my limited
understanding is that a 5ohm or 10ohm resistor can be connected between
the +5V wire (red) and any ground wire. I saw an example a while ago
using the red and black from the IDE connector.

Do I need to jumper the green wire to any black wire (ground) on the
ATX power connector (the long one, 20 way)? This way, if I connect a
resistor using the red and black wires on an IDE connector, and jumper
the green and any black wire on the large ATX connector, I can use the
other yellow and black wires on the connector to power the motor. Maybe
this isn't even necesary if I should use the 4 way 12V power connector.

Regards,

Michael
 
E

Eric R Snow

Hi,

I have a 12V DC motor (6A under load). The only power supplies I have
around here are ATX. Someone at an electronics shop told me they can be
used to supply the power, but I didn't ask how. Is it just a matter of
using an IDE connector to power the motor?

Regards,

Michael
Information from the January 2007 issue of Nuts and Volts column
called Electronics Q&A:
Connect a red wire and a black wire with a 10 ohm 5 watt resistor. If
there is a brown wire connect it to the orange wire. Connect the green
wire to a black wire with a switch. This is the on/off switch. Wired
as above the motor can be connected to a yellow and black wire and
turned on and off with a switch without damaging the power supply. If
you want the motor can be connected without a switch and the 10 ohm
resistor eliminated. Then the power supply on/off switch can be used
to turn the motor on and off. If you do this don't connect the red
wire to anything and don't disconnect the motor when the power supply
is on. Make sure all the unconnected wires cannot make contact with
anything. Here's a web site mentioned in the same column about ATX
power supplies:
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM
All the above info was gleaned from Nuts and Volts and I cannot take
any credit for it.
ERS
 
E

Eric R Snow

Information from the January 2007 issue of Nuts and Volts column
called Electronics Q&A:
Connect a red wire and a black wire with a 10 ohm 5 watt resistor. If
there is a brown wire connect it to the orange wire. Connect the green
wire to a black wire with a switch. This is the on/off switch. Wired
as above the motor can be connected to a yellow and black wire and
turned on and off with a switch without damaging the power supply. If
you want the motor can be connected without a switch and the 10 ohm
resistor eliminated. Then the power supply on/off switch can be used
to turn the motor on and off. If you do this don't connect the red
wire to anything and don't disconnect the motor when the power supply
is on. Make sure all the unconnected wires cannot make contact with
anything. Here's a web site mentioned in the same column about ATX
power supplies:
http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM
All the above info was gleaned from Nuts and Volts and I cannot take
any credit for it.
ERS
WHOOPS! I forgot to add that if the load resistor is used it needs to
be mounted to a heat sink because it will get hot.
ERS
 
M

MK

Hi Eric,

I don't want to open the PSU. Can you give an alternative solution
please?

Regards,

Michael
 
B

BobG

vic said:
Actually it's easy, you just need to ground the /PS_ON signal (pin 14,
usually a green wire).
================================
Hi Vic.... does one need to release and reconnect the button, or does
strapping the green wire to ground enable automatic power on? (I think
I got real frustrated trying to make a gizmo with an atx ps just turn
on)
 
E

Eric R Snow

Hi Eric,

I don't want to open the PSU. Can you give an alternative solution
please?

Regards,

Michael
No need to open up the PS. All the wires come out. Just cut off from
the connector the wires you need. The resistor, if used, can be
mounted to the outside of the PS. Use wire nuts to connect the wires
to your motor, the switch, or each other. I don't know if the on/off
wires need a momentary connection or if they need a continuous one.
Try this: If there is a brown wire cut it from the connector and
connect it to an orange wire. Cut away a black and a yellow wire and
connect to the motor leads. Reversing the wires will reverse a
standard DC motor. Cut away the green wire and another black wire.
Plug the PS into the wall and touch the green and black together
momentarily. If the motor comes on and stays on then buy a momentary
contact switch. If the motor will only stay on with the green and
black wires touching then get a switch that makes constant contact.
Since the above scheme disposes of the resistor do not discionnect the
motor if the PS plugged in. If all the other wires are left in the
connectors they will be unlikely to be able to touch anything. But
just to be sure wrap the connectors with black tape.
ERS
 
J

jasen

Hi Graham,

Ok, thanks for pointing that out. Is the 4 way connector you referred
to the 12V power connector (with 2 black, 2 yellow wires)? If so, is it
just a matter of connecting a yellow and black wire to the motor?

Also, which is the 5V supply? Correct me if I'm wrong, but my limited
understanding is that a 5ohm or 10ohm resistor can be connected between
the +5V wire (red) and any ground wire. I saw an example a while ago
using the red and black from the IDE connector.

Do I need to jumper the green wire to any black wire (ground) on the
ATX power connector (the long one, 20 way)? This way, if I connect a
resistor using the red and black wires on an IDE connector, and jumper
the green and any black wire on the large ATX connector, I can use the
other yellow and black wires on the connector to power the motor. Maybe
this isn't even necesary if I should use the 4 way 12V power connector.

all yellow wires are 12V
all red ones are 5V
black ones are ground.

inside the powersupply they are all hooked together.

I'd suggest using a bunch of the yellow and black wires to power the motor
(maybe 3 of each)

as graham says sticking some sort of load on the 5V supply may help
but I doubt you motor is real fussy on how well the 12V is regulated.
 
E

Eeyore

MK said:
Hi Graham,

Ok, thanks for pointing that out. Is the 4 way connector you referred
to the 12V power connector (with 2 black, 2 yellow wires)? If so, is it
just a matter of connecting a yellow and black wire to the motor?

Basically yes. Yellow is +12V.

Red is the 5V btw.

Also, which is the 5V supply? Correct me if I'm wrong, but my limited
understanding is that a 5ohm or 10ohm resistor can be connected between
the +5V wire (red) and any ground wire. I saw an example a while ago
using the red and black from the IDE connector.

You may need to draw a bit more current than that for the PSU to regulate properly
but I couldn't give an exact figure. 10 ohms would only draw 2.5W and I'm sure that
won't be enough for the supply to be comfortable. Best to experiment a bit.

Do I need to jumper the green wire to any black wire (ground) on the
ATX power connector (the long one, 20 way)? This way, if I connect a
resistor using the red and black wires on an IDE connector, and jumper
the green and any black wire on the large ATX connector, I can use the
other yellow and black wires on the connector to power the motor. Maybe
this isn't even necesary if I should use the 4 way 12V power connector.

Yes, one of the other posters mentioned the relevant wire to ground to turn the power
on.

Graham
 
M

MK

Ah, something I didn't mention is that I'll be connecting a motor
controller and a counter kit to counter the rotation also. All these
can be powered by 12V, so they may or may not be fussy. Anyone have
thoughts on issues with this setup? For example, I the PSU can manage
11.5V, how will it affect the kits and motor?

Regards,

Michael
 
J

jasen

================================
Hi Vic.... does one need to release and reconnect the button, or does
strapping the green wire to ground enable automatic power on?

If you connect them together permanently it'll run all the time,
put an on/off switch there and it'll behave as expected.


Bye.
Jasen
 
M

MK

Regarding a load on the 5V supply. Is this really necessary on the
current ATX power supplies. Isn't there a current standard that states
this should be handled inside the PSU? If this is so, then jumpering
the green and black will be all that is really necessary for a current
ATX PSU to run.

Regards,

Michael
 
M

Michael Black

MK" ([email protected]) said:
Regarding a load on the 5V supply. Is this really necessary on the
current ATX power supplies. Isn't there a current standard that states
this should be handled inside the PSU? If this is so, then jumpering
the green and black will be all that is really necessary for a current
ATX PSU to run.
Why do you think that? I've never seen anything about this.

I have seen surplus switching supplies that include load resistors, but
they have nothing to do with the common computer power supply.

Think about it, the one line that will most definitely get loaded is
the one that also just happens to supply the most current, the +5v line.
Undoubtedly the supplies are designed so the load of a motherboard (and
maybe some minor peripheral) is enough so the supply can run. There
is no need for a built in load resistor because the supplies are intended
for a specific appplication, that will be enough of a load.

If they put a load resistor in the supply, it makes it easy for you when
you are using the supply for something other than a computer, but it's
just unwanted heat in the power supply for the use that the power supplies
are designed for. They need those high current supplies because the
computer needs it, so why waste it with a load resistor?

Another way of looking at it comes up every time someone wants to
use a computer switching supply as a general purpose bench supply.
They go through the rigamarole of adding a suitable load so the
switching supply runs, and then use the supply to power something
that barely needs any current. Far better to just throw together
a linear power supply out of scrap that is just intended for the
needed lower current, than waste current with a load resistor in
order to get the switching supply to do something it wasn't intended
for.

Michael
 
M

MK

My apologies, I meant to ask if there was a standard not to imply that
there is one. I may have read or been incorrectly informed that some
ATX power supplies don't need the load on the 5V. Maybe they refered to
the AT supplies.

Making the modifications mentioned here are very simple. I wouldn't
know how to put together a linear power supply out of scrap. However, I
do have ATX power supplies as I stated. If it works, that will do me
for this project till I find something more suitable if I ever do.

There are so many things that have been modified and used as they
weren't intended, that's how most things get off the ground. For
example, if I only used a drill press to drill holes, that would be a
complete waste because that machine has so many different uses. Look
into every field and you'll see things being used in a variety of
different ways. Medication is another. There are many medications which
are used for multiple conditions, with a very long list of side
effects, so what was the original intended use I wonder. You take a
part here, a part there to build things. I've been making various tools
from modifying existing tools, which I'm really happy about for obvious
reasons. Nothing wrong with that as long as risks are mitigated and
safety procedures adhered to.

Regards,

Michael
 
E

Eeyore

MK said:
My apologies, I meant to ask if there was a standard not to imply that
there is one. I may have read or been incorrectly informed that some
ATX power supplies don't need the load on the 5V. Maybe they refered to
the AT supplies.

Making the modifications mentioned here are very simple. I wouldn't
know how to put together a linear power supply out of scrap. However, I
do have ATX power supplies as I stated. If it works, that will do me
for this project till I find something more suitable if I ever do.

You might as well use what you've got for sure !

Graham
 
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