Motor current control circuit with external power transistors

The L165 is a monolithic integrated circuit in Pentawatt ® package, intended for use as power operational amplifier in a wide range of applications, including servo amplifiers and power supplies. The high gain and high output power capability provide superiore performance wherever an operational amplifier/power booster combination is required.

Wiper Speed Control

A continuously working wiper in a car may prove to be a nuisance, especially when it is not raining heavily. By using the circuit described here one can vary sweeping rate of the wiper from once a second to once in ten seconds. The circuit comprises two timer NE555 ICs, one CD4017 decade counter, one TIP32 driver transistor, a 2N3055 power transistor (or TIP3055) and a few other discrete components.


Timer IC1 is configured as a mono- stable multivibrator which produces a pulse when one presses switch S1 momentarily. This pulse acts as a clock pulse for the decade counter (IC2) which advances by one count on each successive clock pulse or the push of switch S1. Ten presets (VR1 through VR10), set for different values by trial and error, are used at the ten outputs of IC2.

But since only one output of IC2 is high at a time, only one preset (at selected output) effectively comes in series with timing resistors R4 and R5 connected in the circuit of timer IC3 which functions in astable mode. As presets VR1 through VR10 are set for different values, different time periods (or frequencies) for astable multivibrator IC3 can be selected.


The output of IC3 is applied to pnp driver transistor T1 (TIP32) for driving the final power transistor T2 (2N3055) which in turn drives the wiper motor at the selected sweep speed. The power supply for the wiper motor as well as the circuit is tapped from the vehicle’s battery itself. The duration of monostable multivibrator IC1 is set for a nearly one second period.

Stepper Motor Controller

The circuit is very simple and inexpensive. This is good thing because most commercial stepper motor controller ICs are quite expensive. This circuit is built from standard components and can easily be adapted to be controlled by a computer. If you use cheap surplus transistors and stepper motor, the price of the circuit can be kept to under $10.


Parts

• R1, R2 ,R3, R4 ------ 4 1K 1/4W Resistor
• D1, D2, D3, D4 ------ 4 1N4002 Silicon Diode
• Q1, Q2, Q3, Q4 ------ 4 TIP31 NPN Transistor (See Notes) TIP41, 2N3055
• U1 ----------------- 1 4070 CMOS XOR Integrated Circuit
• U2 ----------------- 1 4027 CMOS Flip-Flop
• S1 ----------------- 1 SPDT Switch
• MISC ----------------- 1 Case, Board, Wire, Stepper Motor

Notes

• You should be able to substitute any standard (2N3055, etc.) power transistor for Q1-Q4.
• Every time the STEP line is pulsed, the motor moves one step.
• S1 changes the motors direction.

Pulse Width Modulation DC Motor Control

Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it generates heat and hence wastes power. This simple pulse width modulation DC motor control eliminates these problems. It controls the motor speed by driving the motor with short pulses. These pulses vary in duration to change the speed of the motor. The longer the pulses, the faster the motor turns, and vice versa.

Parts

• R1 1 1 Meg 1/4W Resistor
• R2 1 100K Pot
• C1 1 0.1uF 25V Ceramic Disc Capacitor
• C2 1 0.01uF 25V Ceramic Disc Capacitor
• Q1 1 IRF511 MOSFET IRF620
• U1 1 4011 CMOS NAND Gate
• S1 1 DPDT Switch
• M1 1 Motor (See Notes)
• MISC 1 Case, Board, Heatsink, Knob For R2, Socket For U1

Notes

• R2 adjusts the speed of the oscillator and therefore the speed of M1.
• M1 can be any DC motor that operates from 6V and does not draw more than the maximum current of Q1. The voltage can be increased by connecting the higher voltage to the switch instead of the 6V that powers the oscillator. Be sure not to exceed the power rating of Q1 if you do this.
• Q1 will need a heatsink.
• Q1 in the parts list can handle a maximum of 5A. Use the IRF620 for 6A, if you need any higher.
• This circuit is not a true pulse width modulation control. Because only the frequency of pulses varies, it is really pulse frequency modulation. This works, though not as well as true PWM.

AC Motor Speed Controller

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.


Parts

• 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.