AC Motor Speed Controller

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This AC motor speed controller can handle most universal type (brushed) AC motors and other loads up to about 250W. It works in much the same was a light dimmer circuit; by chopping part of the AC waveform off to effectively control voltage. Because of this functionality, the circuit will work for a wide variety of loads including incandescent light bulbs, heating elements, brushed AC motors and some transformers. The circuit tries to maintain a constant motor speed regardless of load so it is also ideal for power tools. Note that the circuit can only control brushed AC motors. Inductive motors require a variable frequency control.

Schematic

Parts

Part Total Qty. Description Substitutions

R1 1 27K 1W Resistor

R2 1 10K 1/4W Resistor

R3 1 100K 1/4W Resistor

R4 1 33K 1/4W Resistor

R5 1 2.2K 1/4W Resistor

R6 1 1K 1/4W Resistor

R7 1 60K Ohm 1/4W Resistor

R8 1 3K Linear Taper Trim Pot

R9 1 5K Linear Taper Pot

R10 1 4.7K Linear Taper Trim Pot

R11 1 3.3K 1/4W Resistor

R12 1 100 Ohm 1/4W Resistor

R13 1 47 Ohm 1W Resistor (See Notes)

C1, C3 2 0.1uF Ceramic Disc Capacitor

C2 1 100uF 50V Electrolytic Capacitor

D1 1 6V Zener Diode

Q1 1 2N2222 NPN Transistor 2N3904

SCR1 1 ECG5400

TR1 1 TRIAC (See Notes)

U1 1 DIAC Opto-Isolator (See Notes)

BR1, BR2 2 5A 50V Bridge Rectifier

T1 1 Transformer (See Notes)

MISC 1 PC Board, Case, Line Cord, Socket For U1, Heatsinks

Notes

TR1 must be chosen to match the requirements of the load. Most generic TRIACs with ratings to support your load will work fine in this circuit. If you find a TRIAC that works well, feel free to leave a comment.

U1 must be chosen to match the ratings of TR1. Most generic DIAC based opto-isolators will work fine. If you have success with a specific part, feel free to leave a comment.

T1 is any small transformer with a 1:10 turns ratio. The circuit is designed to run on 120V so a 120V to 12V transformer will work. Alternately, you can wind T1 on a transformer core using a primary of 25 turns, a secondary of 200 turns, and 26 gauge magnet wire.

R9 is used to adjust motor speed. R10 is a trim pot used to fine tune the governing action of the circuit. R8 fine tunes the feedback circuit to adjust for proper voltage at the gate of SCR1. It should be adjusted to just past the minimum point at which the circuit begins to operate.

R13 must be chosen to match the load. Generally, larger loads will require a smaller value.

Since this circuit is not isolated from mains, it must be built in an insulated case.

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Comments

bilel AC Motor Speed Controller Friday, March 07, 2008 3:03:27 PM

please help me to do my project,its very important to me to continue my high education,i would like to know exactly how to release the 3 phase gradator command card for AC speed controller?THANK U.

anurag tomar AC Motor Speed Controller Tuesday, February 05, 2008 3:42:09 AM

tell me about the project cost and programming criteria

reema AC Motor Speed Controller Wednesday, January 09, 2008 7:30:27 AM

what will be cost of project

paul brown AC Motor Speed Controller Friday, December 21, 2007 6:34:46 AM

a 3 phase motor is really just a large stepper motor, which uses the ac sinewave phases as it's timimg source. essentially to reverse a three phase motor , all you need to do is reverse two of the legs (phases) this can be done with a reversing motor contactor or a dpdt relay wired as an h-bridge. BE VERY CAREFUL 3 phase industrial electricity can kill you,and I've come darn close! that may result if if you don't know what you are doing, you could have a real mess on your hands

kamesh AC Motor Speed Controller Monday, December 10, 2007 3:06:04 AM

can you please give the specific rating or number of the TRI(TRIAC) and U1(DIAC).

Mustafa Edries three phase motor Saturday, November 10, 2007 6:07:24 AM

i need the automatic circuit diagram for a three phase motor turning clockwise and counterclockwise by changing the order of phases.I need the circuit which has a timer and turns the motor CW for 5 minutes then stop for 1 minute and then again turns the motor CCW for 5 minutes.

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bilel	AC Motor Speed Controller	Friday, March 07, 2008 3:03:27 PM
please help me to do my project,its very important to me to continue my high education,i would like to know exactly how to release the 3 phase gradator command card for AC speed controller?THANK U.
anurag tomar	AC Motor Speed Controller	Tuesday, February 05, 2008 3:42:09 AM
tell me about the project cost and programming criteria
reema	AC Motor Speed Controller	Wednesday, January 09, 2008 7:30:27 AM
what will be cost of project
paul brown	AC Motor Speed Controller	Friday, December 21, 2007 6:34:46 AM
a 3 phase motor is really just a large stepper motor, which uses the ac sinewave phases as it's timimg source. essentially to reverse a three phase motor , all you need to do is reverse two of the legs (phases) this can be done with a reversing motor contactor or a dpdt relay wired as an h-bridge. BE VERY CAREFUL 3 phase industrial electricity can kill you,and I've come darn close! that may result if if you don't know what you are doing, you could have a real mess on your hands
kamesh	AC Motor Speed Controller	Monday, December 10, 2007 3:06:04 AM
can you please give the specific rating or number of the TRI(TRIAC) and U1(DIAC).
Mustafa Edries	three phase motor	Saturday, November 10, 2007 6:07:24 AM
i need the automatic circuit diagram for a three phase motor turning clockwise and counterclockwise by changing the order of phases.I need the circuit which has a timer and turns the motor CW for 5 minutes then stop for 1 minute and then again turns the motor CCW for 5 minutes.