Voltage output humidity sensor meter circuit HM1500 / 1520 with microprocessor PIC16F874
Intelligent humidity meter circuit by the HM1500 / 1520 humidity sensor and MCU configuration shown in Fig. The meter + 5V power supply, with four common cathode LED digital tube. CCP
uses three circuit IC: IC1 to HM1500 / 1520 humidity sensor, IC2 is produced by the US microchip band (Microchip) Company 10-bit ADC of microcontroller PIC16F874, IC3 7 Darlington inverter drive array MC1413. PIC16F874 is a cost-effective 8-bit microcontrollers, containing 8 10 successive approximation A / D converter, up to 8 humidity signal analog to digital conversion, is only the way in which. JT is 4MHz quartz crystal oscillators coupled capacitors C1, C2 can be provided after 4MHz clock frequency of the microcontroller. PIC16F874 wide supply voltage range (+ 2.5 ~ + 5V), suitable for low voltage power supply, quiescent current is less than 2mA. RA port (RA0 ~ RA7) for the I / O interface, now use PA0 (also known AIN0) opening line to receive the voltage signal generated by the humidity sensor. PA1 ~ PA4 output bit scanning signal, bit-MC1413 obtained by inverting the drive signal. RB0 ~ RB6 output RB mouth 7-segment code signal, then the corresponding electrode segment LED display pen a ~ g. PIC16F874 also has a power-down protection, MCLR to brownout reset latch side. When UDD from + 5V down to + 4V, the chip enters the reset state. When the power supply has returned to normal, must 72ms delay before the detachment state into normal state. Data during power failure RAM remain unchanged, will not be lost.