im working on a school project that will use 2 Stepper Motors. The objective of the project mainly is to analyze the vibration of a beam. so basicly i have to mount 2 motors at the end of a fixed beam and let the 2 motors turn.
Both motors should be able to run at speed of 300 to 600 rpm and in different phase.
im thinking of using one arduino uno with one Adafruit Motor Shield V2 with capacity 1.2A per bridge and 4.5VDC to 13.5VDC and a power supply. is this combination possible to get that 600 rpm for both motors ? if not what should i change or add? and i think, i can only use one Arduino Uno because i also want the 2 motors to run in different phase..
I help everyone, newbie and experienced alike ... if I can help
The speed of a stepper motor is not dependant on the voltage or current, but the speed of steps. The top speed is dependent on how much "oomph" you can put in each step, ie current which depends on the voltage. You have specified the shield, so you just need motors to match (you did not specify which motors) ie not requiring too much current. A stepper looses strength as the speed goes up. I've seen a note that a NEMA17 will peak at around 600rpm ith 12V (ie stepping faster will not make it go faster), but can cope with almost twice the speed at 24V.
600rpm requires you make a step pulse every 500us - easily done with the Arduino. Even for two.
If you are testing for vibration, remember a stepper generates a lot of mechanical noise. I presume your load test will involve a excentric weight (otherwise the "phase of rotation" makes no sense to me) so you may ned a fancy mounting to dampen the motor contribution.
you are 100% right about that excentric weight.. because we want to set different phase between motors, it is very important that the stepper motors don't lose steps.
i didnt decide which motor because im not sure which motor can give me that 600 rpm. the motor you mentioned NEMA17 can turn at 600 rpm with 12V... but the Adfruit motor shield v2 can only supply 4.5 VDC to 13.5 VDC. So each motor can only get max. 13.5/2 V ie 6.75V. does that means i need 2 motor shield to be stack on each other with one Arduino UNO?
how do i know one motor can turn at which speed on given Voltage?
So each motor can only get max. 13.5/2 V ie 6.75V.
No that is not right at all. Each motor is wired in parallel with the supply so they both get the same voltage.
However that shield is a poor choice for a stepping motor.
You are better off with a chopping regulating driver like this:-
how do i know one motor can turn at which speed on given Voltage?
You look at the data sheet and look at the load on the motor and see where the stall speed occurs for that motor at that load.
If you give 13V external supply to the Motorshield, the shield will supply (slightly less)V to all coils of all steppers as appropiate to step them. This is enough to go 600rpm for a "typical" stepper motor. The Nema17 is probably too big for your needs. "too big" means it will work, but your machine wil be needlessly large/heavy, and the stepper motors own vibrations wll mess up you resuts (of course I do not know how you mecahnically have thought to transfer the rotation to the excentric. If it is via a long flexible "wire" then it may not matter).. The voltage is a requirement for the motor to turn that fast, but it is NOT what regulates the speed. That is done via the step-pulses you send to the motors, from the Arduino, by using the library supplied.
As Grumpy_Mike has pointed out, the Adafruits Motorshield has its limitations - most notably it has no current regulation. The Nema17 is rated at 1.5 A, and the driver chip is rated at 1.2.A.. If you suppy the 13V, the internal reistance is only 1.3Ohms so up to 10A could pass through your motor (ruing the permament magnets) unless your power supply limits it (it proably will) or the chip burns out (blue smoke.... smells bad). So you must only drive it it with a few volts - but then you can not reach speed.
The other driverchip suggested does have a current limit - here you can give it 30 V but it will "chop" (meaning turing the circuit on/off very quickly so the average current is the desired level). There is a small adjusting screw to set the current.
By The way, you do not need to drive the Nema17 with 1.5 A - that is its maximum if you need maximum torque. You probably do not need that. And as I wrote, you can choose other steppers, probably smaller. But you need to read their spec sheet for max step rates (or RPM) voltage and current maximums.
after some reading i ve decided to use the combination of 1 arduino UNO, 2 driver of DRV8825, 2 stepper motors: Trinamic QMot Schrittmotor Hybrid 1,8° QSH4218-35-10-027(Bipolar, 2-phase-motor) which has Rated Phase Current: 1A, Phase Inductance: 4.9mH and max supply Voltage: 42V and 2 Powersupplies:TDK-Lambda LS-75-35 AC-DC Stromversorgung 36 V/DC 2.1 A of 36V/DC and 2.1 A.
i want to supply as much voltage of possible to the motors which is depends on my Powersupply i.e 36V because hope the motor can rotatate more than 600 rpm. do i really need 2 powersupplies? or i can just use 1 powersupply for both drivers and both motors.
You only need all those Amperes if your motors need maximum torque, You have almost no load. (Well, I do not really know. Presumably there is some load as the vibrations you want to induce require energy, ie there is some transfer of mechanical energy from the turning eccentric).
Remember, you adjust the circuit of the DRV8825 to limit the current. (Are you buying the chip, or a board with supporting electronics?) For your experiment you want to supply as little current as possible - this will reduce the vibrations the motor itself generates.
I played a bit with the calculator link you supplied. Notice that as you decrease the current the calculated max speed increases. The calculation is just modelling a "simple" coil. It assumes you must get to Imax. If your speed is higher, then it simply does not get to Imax,, but the motor still turns at the higher speed. This is what the diagrams of the motor manufacture show - as speed increases the torque drops; the torque is proportional to the current and at high speed the current in the coil does not reach max value before it is turned off - that is what inductance does, so to speak. All sort of effects also play in, but the manufacture shows an actual measured curve.
Yes you right... Minimal torque.. Maybe only 50grams cm.
Im buying the chip. So u r saying, if i use only 1 powersupply 36V/DC 2.1A and connect with both chips in series, i will get about 0.5A for each coil with 36V. the I.max from equation will only be 0.5A? And it will give me higher speed and smaller torque..
Will the motor turn if the supply to it is only 0.5A?
If you wire the coils in series there will in effect be only half the voltage available and hence can only go at half the speed. The speed depends on how quickly you can force the current through the coils and that depends on the voltage. The higher the voltage the quicker you can do this and the faster you will be able to go.
I disagree that reducing the current through the coil will allow you to increase the speed. The maximum speed is when the torque is just greater that the stall torque, the more current you have the higher the torque and so the higher the speed.
my mistake.. not in series but in parallel... Parallel was what i wanted to say.... so that the current will devided into 4 ( about 0.5 A per phase) and the voltage stay the same...
but as grumpy said if the current is lower doesnt mean the speed is higher... so my best bet is to supply to the both motors high voltage and current.... means i need 2 powersupplies.
fiera11235:
... And it will give me higher speed and smaller torque..
Will the motor turn if the supply to it is only 0.5A?
The lower amperage does not in any way imply that you get higher speed. I am saying that you can get enough speed even though you limit your current, and the formula-webpage implied that you could not reach full speed if you wanted full current.
The motor will turn with maybe only 100mA. I do not know, but for many steppers "just" turning you do not need a lot of mA. (I cant be bothered right now to read the fineprint in the spec sheet)
If you buy the chip, have you got knowledge/equipment to do the circuit board? I am worried as the discussion so far has shown that your electronics knowledge is not that great. (Nor is mine that great, really, but enough for the projects that I do) I would by something like Pololu - DRV8825 Stepper Motor Driver Carrier, High Current - then it is much simpler. Also worry about the heat from the chip - it needs plenty air or a little heatsink.
