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?
======================================= 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.
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.
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:
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All the above info was gleaned from Nuts and Volts and I cannot take any credit for it. ERS
================================ 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)
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
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.
Yes, one of the other posters mentioned the relevant wire to ground to turn the power on.
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
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.
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.
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