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Magpie
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stepper motor power supply
Presently I power my stepper motor with a 12vdc supply salvaged from an old computer. I'm assuming this is a steady and smooth voltage. It works
well.
However, I suspect that this is not so true with a car battery charger. Its voltage is likely a square wave with narrow gaps of no voltage. There
would also be some ripple I think.
Can a car battery charger be used as a power supply to a stepper motor?
edit: corrected my terminology
[Edited on 28-5-2015 by Magpie]
[Edited on 28-5-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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smaerd
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I'm not sure what you mean by a battery charger?
I use a "wall-wart" (Not this exact one but something similar - http://www.ebay.com/itm/like/191532316781?lpid=82&chn=ps) for my steppers rated for 2A draw. I never use the 2A's but I assume (probably
wrongly) that this gives me more lee-way for source noise.
Pretty sure a computer supply will be one of the smoother options out there. A lot of the really cheap wall supplies have some pretty serious voltage
ripple. This is one of those topics where I will almost always end with saying "I wish I had an oscilloscope".
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papaya
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An Electrolytic capacitor can reduce ripple, however most likely you don't need that. Btw., stepper motors (multi-phase things) are quite different
from classical DC motors(with permanent magnet and rotor), I don't get why you use them interchangeably?
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m1tanker78
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A car battery charger? It can't directly power the stepper motor but it can be switched to run the motor. Car battery chargers tend to have poor
filtering (high ripple) but so do most hobbyist stepper motor drive circuits. It can be cleaned up some with a big capacitor but probing around the
circuit, you'd see a lot of switching noise from the IGBTs or whatever you use in the driving stage.
If you mean a camera battery charger.. probably not. They're pretty wimpy by design. They deliver energy over a greater time but would almost surely
choke even with a small stepper at low advance rate.
Chemical CURIOSITY KILLED THE CATalyst.
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Magpie
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I'm sorry, I mean a car battery charger. And, yes, it's a stepper motor, not a "DC motor."
I would think that for the "12v" setting the output is likely around 13.5v - but I'm just guessing. It's a very old charger likely about 1970 vintage
- it's a Woodward-Schumacher "Electromite," 4 amp.
I suspect that it probably puts out a fairly rough voltage and that is why I asked if it would be suitable for a stepper motor. I would be willing to
try it if doing so would not risk damaging the stepper motor or the driver circuit.
Smaerd, I agree, once again "I wish I had an oscilloscope." 
-------------------------
Measured voltages: 7.6v for the "6v" setting, and 12.6v for the "12v" setting.
[Edited on 28-5-2015 by Magpie]
[Edited on 28-5-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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neptunium
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now you know . . . . oscilloscope arent expansive budd this one cost me a wopping 20 bucks...
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neptunium
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its a hill hopping kind of signal not super steady and probably not great for a stepper motor
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battoussai114
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What kind of battery charger exactly?
Quote: Originally posted by smaerd  |
Pretty sure a computer supply will be one of the smoother options out there. A lot of the really cheap wall supplies have some pretty serious voltage
ripple. This is one of those topics where I will almost always end with saying "I wish I had an oscilloscope".
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For something like checking for ripples from your power supply you could try an arduino or PIC based scope. Or even a Lcsoft Mini Board if you're not
up to programming a MCU, getting components yada yada...
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neptunium
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wal mart crap
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Magpie
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Wow, that's worse than I expected. Thanks for showing that.
My charger is bottom of the line at the time. I bought it at a Holiday gas station in Minnesota. A charger is essential equipment for that state.
The single most important condition for a successful synthesis is good mixing - Nicodem
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neptunium
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what are you running with a stepper motor anyway?
[Edited on 28-5-2015 by neptunium]
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Magpie
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An overhead stirrer:
http://www.sciencemadness.org/talk/viewthread.php?tid=41539&...
I'm currently limited to 12vdc using a salvaged computer power supply. I would like to increase this voltage to 24vdc. I had a wild idea to link in
series the computer power supply with the car battery charger. But based on the replies here that doesn't look too promising.
[Edited on 28-5-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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battoussai114
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Really depends on where you live, a whopping 20$ from ebay plus over 9000 shipping if you aren't in continental US or Canada isn't so good. There are
still other options but they'd certainly get the electronics purists (the sort of people you met on eevblog forum) cringing. 
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smaerd
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If anyone knows where to find one for $20 let me know. That's all I have to say.
Ya battoussai114 I've seen those cheapy variants I actually made a thread about one variety of them which I was excited about but never made the
plunge. http://www.sciencemadness.org/talk/viewthread.php?tid=30483#...
Anyways, Magpie why are you trying to double the voltage?
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Magpie
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I want more speed. Right now I'm limited to 221 rpm. I thought that would be plenty, but when I made salicylaldehyde it was marginal.
The single most important condition for a successful synthesis is good mixing - Nicodem
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neptunium
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this was at a garage sale in Georgia 10 years ago...along with a frequency counter and function generator..keep digging you`ll find one too
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neptunium
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what about 2 car battery in series with a variable resistance to regulate the voltage?
like this old rheostat
http://www.ebay.com/itm/Biddle-Lubri-tact-Slide-Tube-Rheosta...
or a disc kind
http://www.ebay.com/itm/Wirewound-Ceramic-Potentiometer-Adju...
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Magpie
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I placed a 6v lantern battery in series with my 12vdc (salvaged from a computer) power supply giving 18vdc. With 18vdc the stepper motor rpm ran at
320 rpm with good torque. This compares to 221 rpm max speed without the added 6v. Torque fell off badly at higher speeds (up to 800 rpm).
This was a proof-of-principle test. If I had another 6v battery I would try for 24vdc.
The single most important condition for a successful synthesis is good mixing - Nicodem
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smaerd
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So I know you have a 12V line on your old computer PSU, but don't you also have 5V and 3.3V lines? Why not hook those puppies together and pull out
20.3V? It's not 24V but it should be stable, still one plug/supply. Edit - nevermind probably not the best idea, something tells me this will burn a
supply.
Alternatively you could buy a second computer PSU and hook up two of the 12V lines.
[Edited on 29-5-2015 by smaerd]
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aga
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The waveform on your 'scope is that of a Half-rectified transformer output.
Car battery chargers generally have a crude germanium diode stack with lots of cooling fins between (open it up and have a look).
The transformer is OK.
Just replace the germanium thing with a 35A Bridge rectifier and a stack of capacitors after it and the voltage will be more than steady enough for a
stepper/stirrer.
[Edited on 29-5-2015 by aga]
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Magpie
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Smaerd, I don't think that would do any good. The PSU taps have a common ground.
I bought a 2nd cheap lantern battery and placed it in series with the 12vdc PSU and the other 6vdc lantern battery. This gave me 410 rpm with good
torque. A crude measurement with a dca meter having gradations of 1 amp indicated ~ 0.5 amp draw.
Then I filled a 1 liter beaker with ~ 300 ml of water and stirred it with the 24dcv power. It rotated at a smooth 900 rpm! The steady load gave much smoother speed settings.
The above tests were for the advancement of science. I would likely need a source capable of more amp-hours for an extended stirring time, say 1 or
more hours.
[Edited on 29-5-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Zombie
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| Quote: Originally posted by Magpie | I'm sorry, I mean a car battery charger. And, yes, it's a stepper motor, not a "DC motor."
I would think that for the "12v" setting the output is likely around 13.5v - but I'm just guessing. It's a very old charger likely about 1970 vintage
- it's a Woodward-Schumacher "Electromite," 4 amp.
I suspect that it probably puts out a fairly rough voltage and that is why I asked if it would be suitable for a stepper motor. I would be willing to
try it if doing so would not risk damaging the stepper motor or the driver circuit.
Smaerd, I agree, once again "I wish I had an oscilloscope."
-------------------------
Measured voltages: 7.6v for the "6v" setting, and 12.6v for the "12v" setting.
[Edited on 28-5-2015 by Magpie]
[Edited on 28-5-2015 by Magpie] |
I only read this thread to this post (so far)
You can buy an O scope for 40 bucks now on Fleabay.
They have hand held versions similar to multi meters, and they are as easy to use.
I'm guessing someone pointed this out already.
I'll read the rest of the thread.
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Magpie
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After getting the astounding 900 rpm from 24vdc stirring water I tried it with 18vdc. Here again an astounding, smooth 700 rpm stirring water.
This is a much better solution than buying a different NEMA 17 stepper motor.
The Chinese offer a 2a, 24vdc power supply with 120vac input for $17. Free shipping, but it comes on a slow boat.
I am tempted, instead, to buy a more expensive but versatile power supply that could be set at constant amps or constant volts. This would be
multi-purpose with the intent to some day do some syntheses using electro-chemistry.
I would also like to buy an oscilloscope. I can't justify these toys unless I can forsee occasional use. I ran out of storage space long ago. I now
compete with my wife: she buys yarn, I buy lab toys.
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Could this work for a stepper motor?:
http://www.amazon.com/LEDwholesalers-Power-Supply-Under-Coun...
I realize that this is a "switching" power supply and is different from a "linear, regulated" supply.
[Edited on 30-5-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Bright Spark
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Could this work for a stepper motor?:
Yes as long as the motor and its driver add up to less than 48W (2A*24V)
What is the wattage of your motor?, a car battery charger outputs more than 12V just like an alternator, it has to be higher than the battery voltage
in order to drive some charge into the battery, its like a trickle charge
I am unsure why you had the trouble you did but I think the motor could be too much power and hence it dragged the power down, it most certainly
should be a solid DC source with no square wave like look where theres periods of no voltage, this is the sign of a defective supply or internal
protection is kicking in and out
A switching power supply is better in everyway except for reliability, for the user of equipment the difference between switching supply and linear
supply is unimportant just as long as it delivers the power required
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Magpie
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I don't know the watt rating of my NEMA 17 stepper motor. I salvaged it from a Savin copier.
Can the negative terminal of the SMPS be tied to an earth ground?
The single most important condition for a successful synthesis is good mixing - Nicodem
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