The temperature sensor chip, DS1820 is connected to PD1 with a 4.7kpull-up resistor. The PNP transistor can be any types of small signaltransistor. The common anode pin for each digit is controlledby PORTD, i.e., PD2-PD5. PORTB sinks forward current of each LED segmentthrough a 220 Ohms resistor. The circuit diagram is straight forward, similar to 89C2051Clock Circuit. Of course the LED module was designedfor CLOCK display, so you may interested in writing C program for bothClock and Temperature display after built this project. The 2nd picture shows a samplecircuit using universal PCB, see the upper right, it was 10-pin headerfor STK200 compatible downloader. So I spent my freetime weekend puttingthem together, “the AVR Thermometer”. I thought,my friend gave me the AT90S2313 chip, and with a simple homemade ISP cableand a free software AVR ISP downloader, so we don’t need the device programmer.Also I got the DS1820 from my friend. The moduleprovide a prewired multiplex of 4-digit common anode LED, that’s great.See the soldering pad of these signal in the 1st picture below. I bought the LED module from BanMor’ last week, just 30Baht.
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May 2023
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