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application scheme
Motor control and drive

electric motor

date: 2019-08-29
view count: 13

The Motor drive of a film camera is a general term for a small Motor or spring and its accessories assembled in a film camera.Clap a lattice and connect clap can alternate, connect clap when general one second clap 3-5 lattice.Depending on the type of camera, change the back cover to a long film cartridge to take 250 frames.In addition to the use of soft wire remote photography, can also be connected to the timer interval controller automatically shoot, or rely on the control of the shutter, wide application.Automatic film reeler may be used if continuous beating is not required.



In the design of dc motor drive circuit, the following points are mainly considered:

Function: the motor is one-way or two-way rotation?Do you need speed regulation?For one-way motor drive, as long as a high-power transistor or field effect tube or relay drives the motor directly, when the motor needs to rotate in both ways, h-bridge circuit composed of 4 power elements can be used or a double-pole double-throw relay can be used.If you do not need speed regulation, as long as the use of relay can;But if you need speed regulation, you can use transistor, fet and other switching components to achieve PWM (pulse width modulation) speed regulation.



Performance: for PWM speed motor drive circuit, there are mainly the following performance indicators.


1) output current and voltage range, which determines how much power the circuit can drive the motor.


2) efficiency. High efficiency means not only saving power, but also reducing the heating of drive circuit.To improve the efficiency of the circuit, we can start from ensuring the switching state of the power device and preventing the common conduction (a problem that may occur in h-bridge or push-pull circuit, that is, two power devices conducting at the same time makes the power supply short circuit).


3) influence on control input.The power circuit should have good signal isolation on its input end to prevent high voltage and large current from entering the main control circuit, which can be isolated by high input impedance or photoelectric coupler.


4) influence on power supply.Common state conduction can cause instantaneous drop of power supply voltage and cause pollution of high-frequency power supply.Large currents may cause the ground to float.


5) reliability.The motor drive circuit should be as safe as possible, no matter what kind of control signal is added and what kind of passive load is added.


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