Hi guys.I recently bought an arduino uno and im a complete newb, so be prepared for silly questions.I need to control the speed of an single phase induction motor (not less than a 400w , no more than a 1kw, 220v 50hz).
So i was thinking:
control the voltage using igbt (with digital pin and optocoupler)/triac
read the rpm via hall effect sensor
with potentiometer and analog pin set a value for the rmp (0-1023)/ if not possible then a button to add or reduce the set rpm will to the job i guess
both(set and real rpm) shown on a lcd
lets say set rpm value to 500rpm - then the arduino reduces/increases the voltage until the motor gets to 500 rpm.If a load slows the motor , then more current i applied and the other way around, so the rpm is kept steady.What time does it take to sensor the rpm and control the voltage.And will it be able to keep the rpm steady?Is is even possible at all?
Sorry for my poor english 
You cannot effectively control the speed of a single phase induction motor of the power range you refer to. Motors in that range are either capacitor-start with an internal switch or are capacitor start, capacitor run with an internal switch. The switch is centrifugal and requires the motor to reach a specific speed to switch out the start windings.
you would be better off with a variable speed motor since the speed of an induction motor is part of its internal design i.e. poles and windings maybe a complex variable frequency drive
Thanks for the advices 
, but what i really asked was are the codes possible?
You can't vary the speed of an AC induction motor by varying the voltage, you have to vary the frequency, if you want a 50Hz motor to run at half speed you have to lower the frequency to 25Hz and that's not easy or cheap.
nedkol2a:
Thanks for the advices
The codes are possible but they won't work to vary the speed of a single phase induction motor.
And its worse that you might imagine - try to drive an induction motor badly and the current
that flows might be way higher than is safe and start a fire (or melt the fusible link embedded
in the windings that is there to prevent fires).
you can control the speed of a single phase Capacitor start motor using variable voltage. the normal speed controllers are thyrister based and does the job quite well except for the humming sound due to the switching
of the thyristers.
However I am working on avoiding the capacitor and starting the motor with the arduino and control the speed as well.
With a PWM sine wave, it is possible to control the two phases at 90deg each to start the motor.
The speed can be controlled again by varying the voltage.
Watch out for motors where the two coils are unequal though.
And you mean varying the voltage and frequency, V/f should stay constant to keep the current
from changing too much. The current is limited by the very large inductance of the windings only,
so its important to reduce voltage as frequency decreases or you will simply cook the windings.
technobucks:
you can control the speed of a single phase Capacitor start motor using variable voltage. the normal speed controllers are thyrister based and does the job quite well except for the humming sound due to the switching
of the thyristers.However I am working on avoiding the capacitor and starting the motor with the arduino and control the speed as well.
With a PWM sine wave, it is possible to control the two phases at 90deg each to start the motor.
The speed can be controlled again by varying the voltage.
Looking forward to reading how effectively you managed to control a 'conventional' single-phase motor in the power rating specified in the original enquiry.
Looking forward to reading how effectively you managed to control a 'conventional' single-phase motor in the power rating specified in the original enquiry
I believe the phrase that best states how long you'll be waiting for a meaningful response is "when hell freezes over"
avr_fred:
I believe the phrase that best states how long you'll be waiting for a meaningful response is "when hell freezes over"
Going a bit off topic but your comment reminded me of this story :
Is Hell exothermic or endothermic?
Hell from an engineering approach
The following is an actual question given on a University of Washington engineering mid term. The answer was so profound that the Professor shared it with colleagues, which is why we now have the pleasure of enjoying it as well.
Bonus Question: Is Hell exothermic (gives off heat) or Endothermic (absorbs heat)?
Most of the students wrote proofs of their beliefs using Boyle's Law, (gas cools off when it expands and heats up when it is compressed) or some variant. One student, however, wrote the following:
"First, we need to know how the mass of Hell is changing in time. So we need to know the rate that souls are moving into Hell and the rate they are leaving. I think that we can safely assume that once a soul gets to Hell, it will not leave. Therefore, no souls are leaving. As for how many souls are entering Hell, let's look at the different religions that exist in the world today. Some of these religions state that if you are not a member of their religion, you will go to Hell. Since there are more than one of these religions and since people do not belong to more than one religion, we can project that all souls go to Hell. With birth and death rates as they are, we can expect the number of souls in Hell to increase exponentially.
Now, we look at the rate of change of the volume in Hell because Boyle's Law states that in order for the temperature and pressure in Hell to stay the same, the volume of Hell has to expand as souls are added. This gives two possibilities:
If Hell is expanding at a slower rate than the rate at which souls enter Hell, then the temperature and pressure in Hell will increase until all Hell breaks loose.
Of course, if Hell is expanding at a rate faster than the increase of souls in Hell, then the temperature and pressure will drop until Hell freezes over.
So which is it? If we accept the postulate given to me by Teresa Banyan during my Freshman year, "...that it will be a cold day in Hell before I sleep with you." and take into account the fact that I still have not succeeded in having sexual relations with her, then, #2 cannot be true, and thus I am sure that Hell is exothermic and will not freeze."
This student received the only A.