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This post is about building a 3-digit countdown timer based on Arduino MEGA. Up/Down counter also available at this link. The timer will wait for 3-digit number to be entered via 4×3 keypad and then start counting down to zero. Each count is 1 second long. A number up to 999 seconds can be entered. … Read more
For this project two PIC16F877 MCU’s were used, see project schematics below. Slave PIC runs LEDs decoding and multiplexing code on data received from Master. 7-Segment inputs connected to PORTC,B and common digits anodes to PORTB,A via 2N3906 collectors for current amplification. A generic 0.56” Blue Common Anode LED display were used but any other … Read more
Here is a modified and improved electronic lock design. For Arduino version click here.It is largely based on Digital Lock article, however this time a real electronic lock was used instead of a solenoid. The code is a 4 digit number and is stored in PIC16F876A memory. In order to open the lock all 4 digits … Read more
Measuring current is a relatively simple task that can be done by connecting a shunt resistor in series with the load and measuring the voltage on this resistor. The voltage is proportional to a load current according to Ohm’s law. In order the to get a precise measurement the current sense resistor should be sufficiently … Read more
74HC595 is a discrete shift register IC that can be easily integrated with Arduino platform. Usually shift registers are used to convert a serial data to a parallel output. Additional shift registers can be connected in series extending the number of available I/O’s even more. In this basic setup just one 7-Segment display module with … Read more