Green laser is of the mini-sized design

The AT89S52 block diagram in Figure 2-2 shown below: T-XD, the ALE, T0 clock circuit ROM of RAM of T1, T2 timer / counter CPU parallel interface reset circuit P0 P1 P2 P3 serial interface interrupt system R XD / INT / INT Figure 3.2 AT89S52 is the structure diagram 7 3.3 3.3.1 driver driver circuit circuit program demonstration program: MOS transistor amplification scheme to use PWM to generate high and low to control G pole MOS transistor, thereby controlling the on-off between the D pole and S pole, when D is very and the S pole conduction, electrode positive power supply, negative ground. D pole and S pole disconnect the positive electrode and power supply are connected.  green laser pointer  is with low energy consumption.
Anode through the cathode of the diode leads to the capacitor to charge the capacitor to form a loop. So that you can reach a state of balance and adjust the duty cycle of the PWM square wave on the electrodes at both ends of the current can be adjusted to control the speed of the electrode. Diode freewheeling would seriously affect the power, the power requirement is relatively high, and should not be selected. Option II: the integrated chips L298, L298 is an ST produced a high-voltage, high current motor driver chip. The chip's main characteristics are: high voltage, maximum operating voltage up to 46V; output current, the instantaneous peak current up to 3A continuous operating current of 2A.  green laser pointer  can serve as normal laser pens for teaching.
Contains two H-bridge high-voltage high-current full-bridge driver, can be used to drive two DC motors; standard TTL logic level signal control; both enable the control side, without the influence of the input signal. allow or prohibit the device operates; a logic supply input, the internal logic circuit part of the work at low voltage. L298 15 feet Multiwatt plastic package, available through the heat sink screws on the radiator. L298 internal include: A and B (each of the two H-bridge high-voltage high-current full-bridge driver full bridge of four NPN type transistor); logic circuit power supply regulator; logic control circuit. Its internal electrical department is shown in Figure 3.3. This design circuit can drive two DC motors, low voltage and low current signal to control higher voltage and high current.  green laser pointer  creates a healthy teaching environment.
Electrical high-power, high will single-chip to produce a more serious interference, not directly to the control signal generated by the microcontroller directly connected to the motor, you need the strength of electrical isolation. In the practical application of the general strength of electrical isolation electronic switch method or the method of optical isolation. Since electrical work requires a greater power, so often need to use the power amplifier to provide the motor operating current, the weak signal sent by the optical isolator into a strong signal, you can use the integrated amplifier can also be used discrete components. Here less cost, and simple circuits and high reliability optical coupling chip 4N25, separated by this design enables single-chip power supply with the motor power supply, greatly enhance the stability of the system.  green laser pointer  is very easy to carry.
3.3.3 Motor Control (1) DC motor working principle of DC motor consists of two parts of the stator and rotor, equipped with a pole on the stator, the electromagnetic DC motor stator poles around the field winding. Its rotor is made from silicon steel laminated rotor cylindrical slot, the slot is embedded in the armature winding, winding through the commutator and brush leads. Figure 9 Figure 3.5 DC motor structure in the excitation DC servo motor, the motor speed is determined by the armature voltage, excitation voltage and the load torque is constant, the higher the armature voltage, the faster the motor speed; armature voltage dropped 0V, the motor stopped; change the polarity of the armature voltage, electrical steering changed.  green laser     is of the mini-sized design.