PIC16F73 PDF

Whilst most people considered the CP a good CPU, it had one significant problem; to reduce pin count of its physical DIP packaging, the address bus and data bus shared pins. This meant that communicating with a device required the device to watch for key memory locations being accessed on one machine cycle, and then read the data on the next. All of this complexity was repeated on the CPU side in the corresponding device driver. To address this shortcoming of the , the 8-bit PIC was developed in After the [ edit ] In , General Instrument sold their microelectronics division and the new owners cancelled almost everything which by this time was mostly out-of-date.

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WhatsApp Advertisement At a time, only one of the switches is turned on. Current will flow from the positive side to the switch and then through the fan load to the junction point of C1 and C2. The flow of current is from right to left through the load.

This current constitutes the positive half cycle. When switch S2 is turned on using the second set of pulse sequence, the current will flow from left to right side of the load. This current constitutes the negative half cycle. In this manner, the alternating current of the frequency generated by the PWM waves will be applied to the fan. When you apply 60Hz, the motor speed increases. Using the microcontroller, you can vary the frequency from 40 to 70Hz. It is not advisable to increase the frequency for the fan motor beyond this value.

Generating the AC sine voltage at variable frequency The variable frequency sinusoidal waveform is generated for positive and negative half cycles by closing switches S1 and S2 alternately.

S1 is switched on and off as per the pulses from PWM1, whose width varies as per Fig. This goes for one half cycle time, which is 20ms for 50Hz current, 16ms for 60Hz current and so on.

Then, the next half cycle is obtained by sending current, using switch S2, in the opposite direction through the motor coil. Switch S2 is also repeatedly closed and opened as per the pulses coming from PWM2 pin. Now the main challenge is to choose the transistors for S1 and S2. So bipolar transistor version is chosen here. You can preferably use Darlington bipolar transistor rated V or more. Transistor MJE is a good choice with its voltage rating of V, gain of and maximum current rating of 8A.

But, it is expensive. So a compromise has to be made. In order to switch on the transistors using PWM pulses, use of optoisolators is necessary. When the pulses of current are sent to the LED in the optoisolator through a resistor, the phototransistor inside turns on.

This transistor is connected across the collector to the base of the switching transistor. So, each pulse turns on the switch for the duration equal to the pulse width and passes current through the motor coil connected between the two junction points—switches and capacitors as in Fig.

The choice of the optoisolator is critical in two ways. First, it should have a phototransistor resistance such that adequate current flows through the base of the switching transistor. Second, its off-state voltage rating must be V. Triac drive optoisolator MOC can also be used. Fan speed regulator circuit Having seen how the switches are turned on by PWM1 and PWM2 pulses so as to generate variable-frequency sine wave current into the coil, the block diagram shown in Fig.

Use of an IR remote is optional. PWM pulses coming from its pins 12 and 13 have to be checked on a scope. An R-C filter can be used to see the sine waveform as shown in Fig. By varying potentiometer VR1, you can change the frequency of the sine wave. For ceiling and table fan loads, if H11D1 optoisolator is used, switching transistors can be MJE or The upper section of fan speed controller circuit shown in Fig.

But after mains supply is given to the bridge, it is dangerous to touch any part of the circuit. Turn on the circuit using VR1 with its knob. In Fig. The circuit is very simple to wire.

You can even assemble it on a breadboard as transistors are 3-pin TO type. Use suitable heat-sinks for transistors T1 and T2. After wiring the circuit, switch on the AC mains power. It is advisable to use a variable auto transformer first and vary the voltage slowly from V. Otherwise, the fuse may blow up at startup if there is any wiring fault.

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WhatsApp Advertisement At a time, only one of the switches is turned on. Current will flow from the positive side to the switch and then through the fan load to the junction point of C1 and C2. The flow of current is from right to left through the load. This current constitutes the positive half cycle. When switch S2 is turned on using the second set of pulse sequence, the current will flow from left to right side of the load. This current constitutes the negative half cycle.

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Fan Speed Increasing Regulator Using PIC16F73

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