There are several video clips in youtube that show how to run a stepper motor with a capacitor. Here is one of the video:
I am not agree with that.There is no real formula. Like Max said you need to experiment...
But you can do it by testing a few with a range between them. You find what is close, then you test within that range, to find the best fit. Like what Max said in his first post you use a capacitor/resistor substitution box https://www.nutsvolts.com/magazine/article/September2016_Capacitor-Resistor-Substitution-BoxesWhen an engineer plan a circuit,first,he chooses all components value according to calculations that he makes.After that,he test the circuit and fix what he needs to fix/change.You can't just take 100 capacitors and test each one with the circuit.
Max answered this in post #7 -Do you want to say,that it is impossible to calculate the capacitor value that will make the rotor spin?at least the the value that i can start with?
Nothing like this is impossible, it just takes some thought and common knowledge. And experimentation since your doing something that isn't very well documented.Alternately, measure the inductive reactance at 50hz/60hz and chose a capacitor to produce the 90°.
Unfortunately, it is impossible to simulate your motor, because you did not tell us inductance value of coils.So,how can i calculate(formula)the right value of a capacitor for a stepper motor based on my attached diagram? For example:12v/30mA stepper motor,each coil is 410 ohm.
The phase inductance is 130mH.Unfortunately, it is impossible to simulate your motor, because you did not tell us inductance value of coils.
For this inductance and R_coil=410 Ω, capacitor should be 60 uF,The phase inductance is 130mH.
Capacitors must be non-polarized.Did they choose the polarised cap on purpose or i can use also the non-polar cap?
Easy. It is possible, if R_L=X_L or R_L<X_L.So,how can i calculate(formula)the right value of a capacitor for a stepper motor based on my attached diagram?
@xchcui, below is highly recommended by @MaxHeadRoomStill does not look right, compared to the SloSyn example motors.
So,do you mean,that i should build the circuit as we can see a bove:
I did not say "you should build this circuit".So,do you mean,that i should build the circuit as we can see a bove:
while L1 is in parallel with L2 which is in series with a non-polar capacitor(650 nano farad),but without the resistor(R1)that is shown in your last diagram?
Right.The source of this circuit,while you made the simulation is 12VAC 50Hz,
LTspice did not take into account some electrical and electromechanical parameters of motor, so circuit may need to be tuned with help of oscilloscope.Can we trust on the capacitor value(650nF)that LTspice software simulation gave us?What is the range value of capacitors that should i buy in order to cover and fix a possibility that the capacitor value(650nF)is wrong?
Danko.I did not say "you should build this circuit".
Buy these capacitors and experiment with them:am not sure how to choose the proper capacitor value
This begs the question of why your even using this motor? And if you have to use this motor why you aren't just using a stepper motor driver to do it? Just because it's called a "stepper motor" doesn't mean it can't or won't rotate at a set RPM if the driver is used at the correct frequency. A stepper driver is very inexpensive on Ebay or Amazon and is ready to work when you get it.All i need is to make the motor spin for 2 minute with a load(that contains a set of plastic gears)in order to test
them.Thats all.Not to make it spin permanently.
Thanks for your links.Buy these capacitors and experiment with them:
120pcs 50V 15 Values 1uF - 2200uF Electrolytic Capacitor Assortment Tool Set.
$4.99 for set.
Or 120pcs 12 Values 1uF-470uF Assorted Electrolytic Capacitor Assortment Kit Radial.
US $2.45 for set.
View attachment 209341
C1 and C2 should have same value.
Couple C1, C2 works as non-polarized capacitor.
This motor is came together with the set of the plastic gears.This begs the question of why your even using this motor?
Because i don't have a stepper motor driver and i am not going to buy a driver only to test something one time.And if you have to use this motor why you aren't just using a stepper motor driver to do it?
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