stepper power supplies
Mike W
Posts: 105
I am looking for a schematic for a power supply to drive two stepper motors.
They are SHINANO KENSHI STH-56D series motors. They are marked
on the motor as 1.4 Volt 2.6 Amp
I will be driving them with a SX28 so all I am looking for is a power supply circuit.
Does any one have advice or suggestions.
Thank you
Mike
They are SHINANO KENSHI STH-56D series motors. They are marked
on the motor as 1.4 Volt 2.6 Amp
I will be driving them with a SX28 so all I am looking for is a power supply circuit.
Does any one have advice or suggestions.
Thank you
Mike
Comments
-Phil
They are 8 wire motors I believe they are Bipolar permanent magnet
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The circuit I am thinking about would be simular in design to a ULN 2803
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Just a basic switch I think
I want to drive a (TRANSISTOR, SCR, MOFSET) or what ever device will handle the current
and switch power on and off to the servo magnets with a signal from the SX28 just like I am doing
with the smaller motors and the use of the ULN2803
·
If this is at all possible
Thanks
Mike
That said, the simplest way to operate these would be with a hefty 5V power supply and a couple of power resistors. Since it's not clear from the spec how many coils are energized when it's drawing 2.6A, you will need to measure the resistance across one coil. Let's say that value is R. The resistance of each power resistor will have to be about 2.5R, and it will have to be rated for about 5/R watts. These resistors will get hot, and you may need to get the heat-sinkable kind, but they're there for a reason.
When a motor coil is first powered on, it won't draw any current, due to its inductance. The current will build at a rate proportional to the applied voltage. So the more voltage you can apply, the faster you'll be able to energize the coil, and the more speed and torque you'll be able to wring from your stepper motor. With the series resistors, you will initially be applying 5V to a motor that's rated for 1.4V. But this is okay, since it's not drawing any current. As the current builds, the voltage drop across the resistor will increase until it reaches 3.6V, leaving the motor with its rated 1.4V.
You can get by with just two resistors since only two coils will be energized at a time. Each resistor can be shared by a pair of coils that are never energized simultaneously.
-Phil
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Thanks for the clarification I am still unsure about the difference between the two unipolar or bipolar
Anyhow let me see what I can come up with the information you provided
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Thanks again
·
Mike
The 8 leads connected to 4 sets of connections to groups of 2 coils each
I do not know if the coils are wired in series or parallel
The resistance on the pair is about .7 ohms
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I have, looked for a data sheet but was not able to find one.
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Mike
The wires coming out of your motor will probably be divided by color (or exit hole, in the case of "pancake" motors) into two groups. In each group there may be a solid-colored wire and a striped wire. Assuming this is the case, you will want to connect a solid wire with a striped wire from the same group to one of the resistors, with the other end of the resistor going to +5V. The remaining solid and striped wires go to open collector bipolar (or open drain MOSFET) drivers, sequenced in such a way that both coils within a group are never active simultaneously. These drivers must ba capable of handling at least 2A each.
Are you with me so far?
-Phil
so far I am with you, thanks
I will need to order parts but at least now I have a list
Mike
One question before you do: Are you certain about that 0.7 ohm resistance reading? The specs seem to imply 0.54 ohms (1.4V / 2.6A). Since the resistors are so cheap, you might want to get a range of values, say, 1.5, 1.8, 2.2, and 2.7 ohms. Also, if your reading was too high, I'd get a heftier power supply, too, say 6A instead of 4A.
When you get the resistors, start with the highest-valued one, apply 5V through it to one of the wire pairs, and measure the voltage across the coil. If it's less than 1.4 volts, try the next size down, and so forth. This will be more reliable than measuring the coil resistance since, at such a low value, probe resistance becomes a factor in the measurement.
-Phil
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To get back to my post
Actually I used another ohm meter and got a reading on one coil of .6 ohms
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The range of values is a good suggestion, plus I could always use more parts.
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I dug around and found a “ DIGITAL POWER CORP” power supply I had.
It will do + 5 ·volts at 15 amps (plus several other + and – voltages) I am hoping
·it will do the job.
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You said “open collector bipolar (or open drain MOSFET) drivers”?
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Would you have a suggestion as to a device?
Compatible with a 5 volt input from an SX 28
and a 2 - 5 amp rating.
Thanks
Mike
-Phil
IRL 520_ND I was going to go with these.
I have attached a schematic that is what I think I need to do.
I am not sure about the diodes.
Will a 1N4002 work, or is their a better diode??
Do I need both diodes?
Are they aimed the right way?
I will duplicate this for each coil, with the exception that each power resistor will power two MOSFET’s.
The FindChips web site (link below), usually used for locating suppliers for integrated circuits, can also be used for locating suppliers for other semiconductors as well. There are a number of suppliers which show up for the MOSFET you are seeking. Here is a link to that search engine: http://www.findchips.com/
Regards,
Bruce Bates
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DigiKey carries the IRLZ34. The IRL520 should also work; but you may need a heatsink for it, since it will be dissipating more power (~3/4W), due to its higher "on" resistance. It may also be necessary to adjust your series resistor as an additional consequence.
In your schematic, D1 is probably unnecessary, since a reverse body diode is part of the MOSFET itself. Also, add a resistor (10K) from the gate to ground to hold the MOSFET "off" while the SX pin is tri-stated during powerup.
-Phil