Stepper Motor Experiments Stepper Motor Experiments Stepper motors are most commonly controlled by microprocessors or custom controller ICs and the current is often switched by stepper motor driver ICs or power transistors. Precise motion is possible but the complexity usually lands the hobbyist's stepper motors in the 'maybe someday' parts bin. But steppers may be used for a variety of applications without complex circuitry or programming. At first glance the stepper motor looks a bit intimidating since there are at least four wires and often there are six.

Most steppers have two independent windings and some are center-tapped, hence the four or six wires. A quick ohmmeter check will determine which wires belong together and the center-tap may be identified by measuring the resistance between the wires; the center-tap will measure 1/2 the total winding resistance to either end of the coil. Tie the wires that belong together in a knot and tie another knot in the center-tap wire for easy identification later.

Stepper motors have become quite abundant and are available in all shapes and sizes from many surplus dealers. Experimenters can also salvage excellent steppers from old office and computer equipment. Steppers move in small increments usually indicated on the label in degrees. To make a stepper motor spin in one direction current is passed through one winding, then the other, then through the first winding with the opposite polarity, then the second with flipped polarity, too.

This sequence is repeated for continuous rotation. The direction of rotation depends upon which winding is the 'leader' and which is the 'follower'. The rotation will reverse if either winding is reversed.

The center-tapped versions simplify the reversal of current since the center-tap may be tied to Vcc and each end of the coil may be alternately pulled to ground. Non-tapped motors require a bipolar drive voltage or a bit more switching circuitry. If current is applied to both windings, the stepper will settle between two steps (this is often called a 'half-step'). Taking the half-step idea to the extreme, one could apply two quadrature sinewaves to the windings and get very smooth rotation. This technique would not be particularly efficient since the controller would be dissipating at least as much power as the motor but, if smooth motion is required, it might be worth a try! Or, for those who don't mind complexity, the sinewaves could be efficiently approximated by using variable duty-cycle pulses.

But the purpose here is to get those motors out of the junk box, not to think of more reasons to leave them alone! So here are some simple things to try. Steppers make excellent low power generators and surprisingly efficient low power motors for low RPM applications. As a starting point, try connecting the windings of two steppers together.

Jun 26, 2017. Board is a driver for 5 phase stepper motor. The supply voltage is 400 volts it should be converted to DC & filtered pure & then switched to motors windings.

Pick steppers that turn freely so that internal friction doesn't spoil the experiment. When you spin one motor shaft, the other will follow. Admittedly, there is little torque. But it does illustrate that steppers may be used to generate electricity. Here are a couple of sketches showing how to connect stepper motors as generators: The AC windings are not directly connected since the voltages are 90 degrees out of phase and the resulting voltage would be somewhat lower.

Dual isolated outputs are possible if the grounds for each winding are not connected together. Here are a few application ideas: Add a hand crank and bulb for kids' science demonstration. A 24 volt stepper will light a 120 volt nightlight or Christmas tree light. Make a wind-powered anemometer.

Generate a higher voltage by turning a high voltage stepper with a low voltage motor. Run various gadgets including radios, calculators, multimeters, flashers, garage door openers, remote controls, LED flashlights, bike flashers. Achieve extreme isolation - use a long plastic shaft to turn the generator for high voltage isolation or use a line-powered motor to spin a stepper for very high line isolation. A large capacitor may be charged to run low current devices for some time after a few quick spins of the crank.

A voltage regulator may be required for some devices but use an efficient series regulator to conserve power if the affair is hand-powered. Many steppers make excellent low power motors despite the markings on the label. For example, a stepper rated at 16.8 volts, 280 mA consumed only 20 mA when unloaded and driven with bipolar 5 volt squarewaves. Such low currents may be directly extracted from many op-amps and logic devices without any additional drivers!

Obviously the mechanical load must be light and the speed will be low or the motor will stall but many useful applications exhibit little load. Here are some examples: Use vanes to mechanically chop light, electrostatic fields or other radiation. Spin a sign or attention-getting symbol on an advertising display. Spin a toy radar antenna or make a highly efficient electric toy car or train. Make a spinning Christmas tree ornament.

Make a laborator stirrer. The following circuit is commonly called a quadrature oscillator or a sine - cosine oscillator and may be built using almost any op-amp with reasonably high output current. An LM358 actually worked in this circuit, but only barely! A better choice would be an LM833 or any one of many higher current op-amps. The two transistors generate Vcc/2 so that the current in the windings will reverse when the op-amps go high and low.

They are not needed if a dual polarity power supply is used. Simply ground the windings that go to the emitters. A motor rated at 16.8 volts and 280 mA consumed only 30mA in the above circuit when unloaded.

Try whatever stepper motor is available and adjust the power supply voltage for proper operation. Don't expect to get much torque from this circuit! For more drive capability connect two transistors to the op-amp outputs in the same manner as the Vcc/2 circuit above. Leave out the resistors and simply connect the two bases to the op-amp output. The two emitters connect together and to the motor winding.

The above circuit is all that is needed for many applications but the following circuit has a bit more flexibility. In this circuit the 74HC74 directly drives the stepper motor for low power applications. The two flip-flops are alternately clocked to give the desired 'follow-the-leader' pulse train. The 16.8 volt motor (1.8 degree step size) described above draws only 20 mA in this circuit and a tiny 15 degree step size, 12 volt motor only draws 30 mA. The unused inverters are wired to form a slow pulse generator which may be used to randomly change the direction of rotation. Actually, the change of direction will often synchronize with the spin oscillator giving a back-and-forth action unless the oscillator frequency is just right. This change of direction will add interest to moving displays.

The circuit generates four control signals and adding circuitry for high power operation is fairly easy. If a center-tapped motor is used then the following connection will work: You will need one of these circuits for each motor winding.

If the motor doesn't have a center-tap then try the circuit below. The values are only representative and may vary depending upon the motor and transistor gain. No provisions are shown to protect against inductive kickback but small motors don't seem to generate much. However, some care may be required if larger motors and higher currents are used. Consider adding diodes from each motor winding to Vcc (the cathode goes to Vcc). Also, the 2N440Xs are only good for a few hundred milliamps so choose heftier transistors and use lower value resistors if higher motor currents are expected. The flip-flop shown is an HC device and its power supply should be limited to 5 or 6 volts but the flip-flop could be a 4000 series device if driver transistors are added.

The 4000 series devices cannot supply much current but they will run on +15 volts. Increase the resistors to 10k and use darlington transistors (or mosfets such as the VN10KM) in place of the NPNs shown. Here is a note sent in by Garin: I appreciate your experimenters internet home site for new electronics nuts. A good source of a ready made 'robot' stepper motor system is an old dot matrix computer printer. Not only does it contain several motors, but it also has in it the electronics to drive them which can be interfaced to your control computer via the parallel port. Old manuals list control codes which can be translated into your application much faster and cheaper than designing your own system. In fact with the advent of color inkjet printers, many old dot matrix PC computer printer can be had for free.

Hopefully this note will be of help.

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: 'Of all the gin joints, in all the towns, in all the world, she walks into mine.' 'Some questions have no answers.' [C Baird] 'There comes a point where the spoon-feeding has to stop and the independent thinking has to start.' [C Lawson] 'There are always ways to disagree, without being disagreeable.' [E Weddington] 'Words represent concepts. Use the wrong words, communicate the wrong concept.'

[J Morin] ' Persistence only goes so far if you set yourself up for failure.' Professor Jones uses a single ended drive in a parallel port. Why do you want to use h-bridge again? I see you're idea. You turn on one coil, then the one cws from it, and it half steps in between the coils, then just the second coil. So there should be 10 positions. Energizing each winding by itself should give 5 steps of 72 deg each.

So if it really 'halfsteps' between poles with 2 coils on, that scheme with 3 coils on wont do anything. The 2 outside coils cancel. Will be the same as the single coil in the middle. Quote: I'm no five-phase expert, but why are you energizing all windings at all times? Shouldn't there be some zeroes in that diagram?

Each coil (coils 1.5) are connected at one end to positive and the other ends are connected to fets. The individual fets turn on with a '+' Logic high to the gate and turn off with a '-' logic Low to tha gate. There are no zeros ust on or off. So basically it's 5 bits of information and that is a possible 31 patterns exclude 11111 and 00000 and you have 29 possible states. Unless their is a difference in the polarity of the individual coils.

Does it make any difference to turn on a coil in the above picture A-Phase Blue positive and red ground or red positive and blue ground? If not then with 29 possible states I intend to find the farthest move to the left and the farthest move to the right of this motor.

If for example the numbers were 5 and 23 then moving from 5 to 23 should move one step in one direction and moving from 23 to 5 the other direction. Then there would be just 8 more to figure out to step from 5 up to 23 in 10 steps.

I will attempt to measure the distance using a 10 inch circle attached to the motor shaft and mark the 10 steps. Not being a numbers guy I think the possible combinations would be 25 bits but finding the maximum and minimum move of the shaft using 1 to 29 should be easy if I can set up a measuring device unless someone tells me the polarity of turning the coil on is different because then you have many more combinations to the puzzle. The sequence is dictated by the design of the unit. Effectively you have to energise the coils in order to drag the poles of the armature around. Polarity of the coils is important - one way you're attracting, the other you're repelling. When you're using a h-bridge drive, some coils are pushing, the others are pulling, using a single ended drive, you're just pulling.

So, i'd say you'd use a 2-1-2-1. Sequence that is two coils on, then one coil on. The sequence would be: 1 0 0 0 1 If the stepper in question is a permanent magnet type, then the polarity will be important. Yes Yes Yes finally, i just finished with testing 5 steps 1,2,3,4,5 then I reversed the polarity on 1 and it went one additional step to the right, it's only 10pm now so by 2am i should have this licked. That's right Kartman I was doing that but not doing polarity, Ahhh I see now the coil is wrapped on a bar and one end pushes and the other end pulls when current flows one way and opposit the other way.

I guess the drawings of stepper motors I have looked at did not make this clear. I will have to take one apart I think to see it. I would think both polls are used to maximize power but perhaps not, i don't have a clear picture of how the magnets align with the coils and the bar that becomes tha magnet when current is pushed through. I guess that means the circuit i posted above from the other guy that said he got it working is simply wrong because you can't reverse the current using this circuit. So I better work on that. Happy 75th anniversary to one of the best movies ever made!

Rick Blane [Bogart]: 'Of all the gin joints, in all the towns, in all the world, she walks into mine.' 'Some questions have no answers.' [C Baird] 'There comes a point where the spoon-feeding has to stop and the independent thinking has to start.' [C Lawson] 'There are always ways to disagree, without being disagreeable.' [E Weddington] 'Words represent concepts. Use the wrong words, communicate the wrong concept.'

[J Morin] ' Persistence only goes so far if you set yourself up for failure.' Just fyi while i was searching for H bridges I found this new not available yet allegro product 8 AMP chip. Looks like a stepper motors drivers dream chip for the do it yourself stepper boards and robot folks. Yes Johan, I was tainted as well. Even the diagram I posted above shows the coils in a way that makes intuitive deduction that current would matter not clear.

This link makes it very clear the arrangement of the electro magnets around the motors magnets and mentions current reversal for those motors that contain more electromagnets. I am still not clear in my head the actual physical arrangement or the magnets and electro magnets in a 5-phase motor but from my experiments it looks like in the full step mode where you turn on phase a,b,c,d,e is the first half of a complete series of steps and then reversing the current starting again with phase a, and continuing with b,c,d,e would complete the series continuing with phase A using the original current flow to start the next series. I have some h bridge 1 amp chips i will connect and put up a complete diagram of how I made a 5-phase stepper work. Thanks to all for responding, many times I post a question on this board and I compete with myself to come up with the answer before someone else does, it helps me focus as 2 or 10 minds are better than one for brainstorming.

Quote: So if it really 'halfsteps' between poles with 2 coils on, that scheme with 3 coils on wont do anything. The 2 outside coils cancel. Will be the same as the single coil in the middle.

You are right, with the exception that the torque will be lower. Metron9, did you try that 20 steps sequence that Professor John talk about? I think it is what you have to do. For tests, you can use that schematic with five transistors. Once you have the system work, make sure the shaft angle is what you expect in your software, you can switch to a better hardware approach. If you include a resistor in series with those diodes in parallel with the coils, will allow you to increase the speed a little bit, because now the magnetic field will vanish faster when the coil is not powered.

Just make sure your transistors have enough room to accommodate the extra voltage. Start with a lower resistor, test with the scope, for the maximum current, and see how far you can increase the resistor, and keeping the voltage spike in a safe area for the transistors.

And then you can switch to a full drive, either with full bridge, either with half bridges and a differential power supply. Since you will have at least two motors, I would invest in a differential power supply, instead to add a multitude of ICs. As for full bridge approach, did you explore L6207 from ST? This IC will accommodate two coils. Wow a resistor in series with the diode, that is cool. Simulation I guess with just a diode you get current flowing in reverse and it looks like with a resistor you just get rid of a high voltage spike and then the current stops dead, is that the theory?

Now how do you go about selecting a resistor value? The higher the value the higher the kickback voltage the transistors have to be able to carry? Nice chip, I have added it to my next digikey order, amazing how much they pack in that thing, current control, overheating safety, everything you need, very cool. I tested the H-bridge connection on the 5-phase motor. One revolution is 1000 steps using this code.

Basically going around clockwise you have 5 coils A,B,C,D,E The Hbridges are connected 1Y,2Y to coil A and so on up to the third Hbridge where its 1Y,2Y are connected to coil E. Turning on 3 coils A,B,C is where step 1 starts. Then A goes OFF in step 2 and C goes on in step 3. Step 4 turns off B and step 5 turns on D when Coil A comes around the current is reversed for the last 10 half steps so there are 20 half steps in this code. I have not seen a 5 poll motor before, but it seems that this gives the user an huge amount of flexibility in both torque and precision. As with any stepper, I assume it will do the standard full step, this gives the least precision.

Also, the standard Half Step should work just as well, giving double the precision. However, if the coils are energized in a 'star' pattern (similar to tightening the lug nuts on a truck) this would give you a one third step, giving you triple the precision!

Also, if you go through the effort to utilize a DAC on each pole and step through sine waves (each precisely out of phase), you could have a huge amount of precision without sacrificing much torque along the way. I may have to get one of these to play with. What Is 12 Strand Dna Activation. Ok, now I know how your motor looks like and why your first approach didn't work. I thought at first you mixed some wires on the motor, and the motor is a 5/2 stator/rotor pole pairs ratio, but I notice it is an 5/1 one. In this case you should use a star connection as someone suggested, and you would need only five half bridges, and not five full bridges. But you need to deal with sin pwm if you want to get rid of the resitors and don't want to have a separate constant current source.

Regarding your question about the resistor in series with the diodes, it is no longer the case, since your resistor is always in series with the winding. In the data sheet is shown the IC has the diodes integrated, but later in an example there are shown external diodes. I would use a more powerfull IC. When you accelerate or decelerate you can exceed the nominal current. If you notice, after one coil is unpowered, it is shorted by both full bridges being at the same polarity. If you want to get rid of the resistor and use pwm, you will face the problem not knowing how to drive the bridges, because you do not have the idle state.

At low speed it is ok to keep both bridges at the same potential, but when you increase the speed, you will need to power the coil in a reverse, to speed the magnetic field decrease. But if you keep too long this reversed voltage, the current will start to rise in a reverse way, and you don't want.

And again, the best way is to drive it with a sinusoidal current. I gave that reverse plolarity a try from 1us to 255 us, around 150us it was too much but at lower times it did not seem to make a difference.

The maximum speed with good power now is 2880 steps per second, that's about 166 RPM. I don't know if that is good or bad as I don't know how fast it should be able to go since I have only worked with 200 step bipolars in full step mode. In the application I planned to use it for is a peristaltic pump using a constant speed. Since when the motor is running 8 Volts works good but when the motor is stopped then 8 Volts is to high and the motor uses too much current. I thought i would try switching a resistor in the ground line using two fets, one with a resistor and one without. Motor running the fet connects directly to ground, with the motor stopped the other fet turns on that has a resistor in series. Mflare Keygen more. I thought about using a variable regulator to turn up the voltage when the motor is running and lower the voltage when it is stopped.

Thank's for the reply I keep poking around long enough I may learn something. Quote: I thought i would try switching a resistor in the ground line using two fets, one with a resistor and one without. Motor running the fet connects directly to ground, with the motor stopped the other fet turns on that has a resistor in series.

I thought about using a variable regulator to turn up the voltage when the motor is running and lower the voltage when it is stopped. Thank's for the reply I keep poking around long enough I may learn something. Try switching from half steps to full steps, and only energize one coil at a time.

This will require some clever code, but I figure it should half the amount of current that is used. Hi KillerSpud. The current I am talking about is the difference between the motor not moving and higher speeds. When you increase the switching speed you need higher voltage to push the current faster into the coils since the time the coil is energized is shorter. For example the motor with 2 or three coils on may draw over 2 amps when stopped and drop to just 350mA when running at 2880 steps per second.

Typically current is controlled throughout the speed cycle. Running at just one speed I should be able to simply switch out a resistor to make it simple. I realized all I need is one fet to ground andthen have a parallel resistor to ground. Switch the fet on when running and turn it off when stopped so the current will then flow through the resistor.