Stepper Motor Circuit with IC 4027

This stepper controller circuit shown here can used to control the unipolar stepper motor,which has 4 coils . The stepper controller circuit can drive for a motor current of up to about 500 mAmp/Winding by suitable heat sinks for the SL-100. directsinks In higher currents power transistors seem 2N3055 can be used as darlington pair along with SL-100. All diodes are used to protect back current the transistor from transients.

Stepper Motor Circuit with IC 4027 Circuit diagram :

Remark. 

• You may be able to substitute any standard (2N3055) power transistor for Q1-Q4 or get IC type UL to modify for transistor.
• Every time in move the motor put signal the STEP line is pulsed, the motor moves one step.
• Switch S1 for changes the motors direction

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Electronic Motor Starter

This motor starter protects single-phase motors against voltage fluctuations and overloading. Its salient feature is a soft on/off electronic switch for easy operation. The transformer steps down the AC voltage from 230V to 15V. Diodes D1 and D2 rectify the AC voltage to DC. The unregulated power supply is given to the protection circuit. In the protection circuit, transistor T1 is used to protect the motor from over-voltage. The over-voltage setting is done using preset VR1 such that T1 conducts when voltages goes beyond upper limit (say, 260V). When T1 conducts, it switches off T2. Transistor T2 works as the under-voltage protector. The under-voltage setting is done with the help of preset VR2 such that T2 stops conducting when voltage is below lower limit (say, 180V). Zener diodes ZD1 and ZD2 provide base bias to transistors T1 and T2, respectively. Transistors T3 and T4 are connected back to back to form an SCR configuration, which behaves as an ‘on’/‘off’ control.

Switch S1 is used to turn on the pump, while switch S2 is used to turn off the pump. While making over-/under-voltage setting, disconnect C2 temporarily. Capacitor C2 prevents relay chattering due to rapid voltage fluctuations. Regulator IC 7809 gives the 9V regulated supply to soft switch as well as the relay after filtering by capacitor C4. A suitable miniature circuit breaker is used for automatic over-current protection. Green LED (LED1) indicates that the motor is ‘on’ and red LED (LED2) indicates that the power is ‘on’. The motor is connected to the normally-open contact of the relay. When the relay energizes, the motor turns on.

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Measuring motor insulation using HI POT tester

What is HI-POT tester?
When we need to evaluate motor condition,HI-POT tester or High Potential tester is the common equipment are used.As we know,a multimeter or ohm meter reading only can determine if a motor winding is open or shorted but cannot checked winding insulation condition if shorted with ground or phase.

The main purpose of the Hi Pot tester is to verify the quality and integrity of the electric motor insulation materials used on the armature or stator and also safe to using it without any defect.
Sometime we not take a serious attention or not know about it to checked winding insulation.This step is important to ensure motor can running in good condition without any breakdown.
Normally electrical motor may have a weakened winding that shorts to ground when it running.It have several caused for the winding breakdown due to the value of system voltage,winding heat build up or overloaded mechanical stress.For other caused it will come from motor terminal board that has an insulation failure from the terminal to ground (earth) or from other terminal for winding connection.

Basic operation of HI-POT Tester
A HI-POT tester produce power source with a high voltage (Volt) and low current (ampere) and it is used to check for an insulation failure for motor winding that the ohmmeter cannot measure with its low voltage power source may miss.
It measures winding insulation resistance to ground (earthing) and terminal board resistance from terminal to ground and from terminal to terminal ( phase to phase )
To get a best result and for safety reason when perform measurement for winding insulation resistance,all wiring is removed from the motor winding terminals.It also same when perform measurement for terminal board resistance, all wiring is removed from the terminal board.
Below is several rules when using the Hi-Pot tester.It is to avoid any serious damage or injuries during insulation measurement and should never be :

1. Operated alone or by an inexperienced service person.
2. Set at a voltage of more than twice the motor operating voltage plus 1000 volts.
3. Be set for more than 5 milliamps without consulting or refer user manual from motor manufacture
4. Applied for more than the time it takes to obtain a reading (no more than a few seconds).
5. Used as a phase-to-phase winding check.
6. For air condition motor compressor,used when the system is in a vacuum.

* SAFETY NOTE : Please read HI-POT tester user manual before using it and refer to the trained or qualified person for assist during measurement.It the best way to avoid any unexpected issued and for safety reason.

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