How hard would it be to modify a power supply to increase amps?

[wolfdagon]

Ok, I was going on something that I read in another thread. Can't find it now, but basically it said that if my motors have 5.2V per phase and 1A per phase then they will actually draw double that because there are two phases, meaning that I would need 10.4v and 2A per motor. It also said that I needed to multiply that by the number of motors to get the correct power supply, meaning 31.2V 6A for three motors or 41.6V 8A for four motors.That's what I have been basing all of my numbers on.

Now then, since it seems that I (and the guy in that other thread) am wrong about this let me give you all the info.

I have three HP LaserJet III motors. They are 5.2V per phase and 1.4A per phase when used unipolar, 1.0A per phase when used bipolar. I plan on using the bipolar with PMINO's L297-8 drives at http://pminmo.com/forsale/1X279805.pdf. If I do add a fourth axis I will use the same kind of motor and drive.

So with this information, and going by what the last few replies have said then one of the 24V 7.2A power supplies would be plenty for my needs, correct? And I could get two and wire them in parallel to get 24V 14.4A and have no problem at all running four motors?

If this is the case I will probably get two of the power supplies even though I will only need one for now. Only three available SDANTONIO.

[holbieone]

if it takes 10.4 volts to drive one motor, that is the voltage the power supply should be

if there is a range on the voltage like 10 to 20 volts go with the higher voltage it will require less amps

if you have any doubts on the amps needed more will not hurt

but to high of a voltage will

[max_imum2000]

ger21
the stepperworld driver use resistors to limit current, other drivers uses PWM or chopper to limit the current
i think thats the reason this is why the motors with stepperworld driver needs full current per winding.

[ger21]

Originally Posted by max_imum2000 ger21 the stepperworld driver use resistors to limit current, other drivers uses PWM or chopper to limit the current i think thats the reason this is why the motors with stepperworld driver needs full current per winding.

I know, I was just clarifying your statement.

[ger21]

Originally Posted by wolfdagon Ok, I was going on something that I read in another thread. Can't find it now, but basically it said that if my motors have 5.2V per phase and 1A per phase then they will actually draw double that because there are two phases, meaning that I would need 10.4v and 2A per motor. It also said that I needed to multiply that by the number of motors to get the correct power supply, meaning 31.2V 6A for three motors or 41.6V 8A for four motors.That's what I have been basing all of my numbers on.

That is incorrect about the voltage. Ideally, you want to use as high a voltage as the drives can handle, up to 15-20x the motors rated voltage. It doesn't matter if you use 1 motor or 4, the voltage stays the same.

The current required, however, will increase as you add motors. I'd ask Phil (pminmo) how much current you need to supply each of those motors, and multiply it times the number of motors.

[pminmo]

Originally Posted by wolfdagon I have three HP LaserJet III motors. They are 5.2V per phase and 1.4A per phase when used unipolar, 1.0A per phase when used bipolar. I plan on using the bipolar with PMINO's L297-8 drives at http://pminmo.com/forsale/1X279805.pdf. If I do add a fourth axis I will use the same kind of motor and drive. So with this information, and going by what the last few replies have said then one of the 24V 7.2A power supplies would be plenty for my needs, correct? And I could get two and wire them in parallel to get 24V 14.4A and have no problem at all running four motors? If this is the case I will probably get two of the power supplies even though I will only need one for now. Only three available SDANTONIO.

Assuming the are six wire motors I would run the bipolar half coil at the 1.4A per phase. Power supply voltage as high as possible with either a safety margin for back EMF or a shunt regulator to prevent over voltage on the L298. Simplest power supply is a 24V 10Atransformer, regulator and capacitor for roughly a 34V power supply. More than enough for your motors. http://pminmo.com/simpleps.htm Without getting into the specifics, current requirements vary, 2 phase on full step requires the most supply current, sine/cosine microstepping only roughly 71% of full step current. As the power supply voltage to coil voltage ratio goes up, the chopper duty cycle declines. Thus the requirements for a switched supply would differ from a linear supply with a beefy filter capacitor.

[wolfdagon]

Originally Posted by pminmo Assuming the are six wire motors I would run the bipolar half coil at the 1.4A per phase.

They are six wire motors, but I'm not sure how to do that. Do I wire the motors to the driver a certain way?

Originally Posted by pmino Power supply voltage as high as possible with either a safety margin for back EMF or a shunt regulator to prevent over voltage on the L298.

I think you have something about the shunt regulator on your website. I'll have to go back there and take a look.

Originally Posted by pminmo Simplest power supply is a 24V 10Atransformer, regulator and capacitor for roughly a 34V power supply. More than enough for your motors. http://pminmo.com/simpleps.htm Without getting into the specifics, current requirements vary, 2 phase on full step requires the most supply current, sine/cosine microstepping only roughly 71% of full step current. As the power supply voltage to coil voltage ratio goes up, the chopper duty cycle declines. Thus the requirements for a switched supply would differ from a linear supply with a beefy filter capacitor.

I'm afraid that most of what you said just went over my head. I think I want to run the motors half step, so does this mean that I take 71% of 1.4A to get 0.994, round up to 1A per phase? And this would mean 2A per motor? If this is the case then for three motors I would need 6A and for four motors I would need 8A, right? The supplies I am looking at are Power-One HE24-7.2-A which are 24V 7.2A. If I wire them in series this gives me 48V 7.2A. You already said that 34V would be enough so I am sure that 48v would be overkill. Would there be any adverse effect using this much voltage as long as I use a shunt regulator as you suggested above? If I am right that 4 motors would take 8A what adverse effects would the 7.2A power supply have?

Sorry if I seem to be going in circles, I just seem to be having trouble wrapping my head around this.

Kenith

[holbieone]

If I am right that 4 motors would take 8A what adverse effects would the 7.2A power supply have?

that's a good question since the motor doesn't use all the windings at once ,it uses them in step

[pminmo]

This should help with the 1/2 coil: http://www.pminmo.com/wiki/index.php?title=6wiremotors
You don't want to run the L298's at 48V, 42V with a shunt regulator would be the maximum I would recommend.
I wouldn't recommend a 24V supply, I'd be looking for 34 to 42V. If they are linear supplies 6A +.

[wolfdagon]

Originally Posted by pminmo This should help with the 1/2 coil: http://www.pminmo.com/wiki/index.php?title=6wiremotors You don't want to run the L298's at 48V, 42V with a shunt regulator would be the maximum I would recommend. I wouldn't recommend a 24V supply, I'd be looking for 34 to 42V. If they are linear supplies 6A +.

Thanks PMINO. After looking at the info at you link, and especially the artcle on the geckodrive website referred to there, I think I finally understand. I will look for a supply in the range you suggest. If I can't find one I will try to build one. I may end up with the 24V supply anyway since I placed a small bid on it already. If so I can at least use it to make sure the motors are running ok until I get the larger supply.

Kenith