This circuit will allow you to control the speed of an AC motor, for example an electric drill. The way that this circuit works is as follows. The bridge rectifier produces dc voltage from the 120vac line. A portion on this current passes through the 10K ohm pot. The circuit comprised of the 10k pot, the two 100 ohm resistors and the 50uf capacitors delivers gate drive of the SCR. The diode D1 protects the circuit from reverse voltage spikes. The ratings of the bridge rectifier and the SCR should be 25 amps and PIV 600 volts. The diode D1 should be rated for 2 amps with PIV of 600 volts. The...

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The circuit shown above can be used to control a unipolar stepper motor which has FOUR coils (I've swiped it off an old fax machine). The above circuit can be for a motor current of up to about 500mA per winding with suitable heat sinks for the SL100. For higher currents power transistors like 2N3055 can be used as darlington pair along with SL100. The diodes are used to protect the transistor from transients. Activating sequence: [code:1:7492cb9d88]+-------------+---------------+ | Inputs |Coils Energised| |-------------+ | | D0 D1 | ...

This circuit can control a small DC motor, like the one in a tape recorder. When both the points A & B are "HIGH" Q1 and Q2 are in saturation. Hence the bases of Q3 to Q6 are grounded. Hence Q3,Q5 are OFF and Q4,Q6 are ON . The voltages at both the motor terminals is the same and hence the motor is OFF. Similarly when both A and B are "LOW" the motor is OFF. When A is HIGH and B is LOW, Q1 saturates, Q2 is OFF. The bases of Q3 and Q4 are grounded and that of Q4 and Q5 are HIGH. Hence Q4 and Q5 conduct making the right terminal of the motor more positive than the...

Physical motion of some form helps differentiate a robot from a computer. It would be nice if a motor could be attached directly to a chip that controlled the movement. But, most chips can't pass enough current or voltage to spin a motor. Also, motors tend to be electrically noisy (spikes) and can slam power back into the control lines when the motor direction or speed is changed. Specialized circuits (motor drivers) have been developed to supply motors with power and to isolate the other ICs from electrical problems. These circuits can be designed such that they can be completely separate...

The simplest of all motor controllers (besides a straight on/off switch) is the contactor controller. Aaron designed this contactor controller for use in his [url=http://www.aaroncake.net/projects/elecscoot.htm]electric scooter project [/url]. It is based around three 12V relays, two 12V batteries, two switches and of course a motor. Having no silicon to "fry", it is quite reliable and robust. A contactor controller works by rearranging the two (or more) supply batteries between series and parallel. This gives the motor a slow speed (batteries in parallel, current adds) and a fast speed...

This cicuit allows you to test a servo. The angle of the servo can be set by means of the 10k potmeter. Perhaps you will not be able to reach all positions with this circuit. Playing with other resistors may help....