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PIC12F675 controlled electrical key-lock

For building 12 button key-lock you don’t need microcontroller with many ports. Ivica Novakovic has a nice demonstration on how low pin count microcontroller with ADC can be used to read many keys. Key-lock itself is simple. It controls two relays where electromagnets or motors can be attached. In key-lock circuit there are only one one wire used to read buttons. Of course there are also VCC and GND (power supply) needed. Author also included simple piezo buzzer for sounding keys. Each keypad is positioned between resistor voltage dividers so when one of buttons is pressed, ADC reads a voltage drop. This way each button provides different voltages when pressed. As there is 10 bit ADC used, there can be 1024 different voltages read, but in reality there has to be voltage range left for one button, because voltage may fluctuate. For 12 buttons each button has 85 value range what is enough for reliable operation. With more precise resistors and stabile power supply there can be more buttons interfaces if needed. Project files and firmware are available for download.[via] Continue reading

AVR Tiny G-force metter

While stumbling around Hackaday projects I found this interesting G-Force measuring project. Project aim was to measure lateral acceleration force of driver in car when turns when he turns right. According to author car can normally handle 0.8g of centrifugal force. Above this value car may slide to the sideways. Well this of course is a matter of tires used and other factors.     Measuring board contains: Atmel ATtiny26 microcontroller; 3×10 LED bars; ADXL103 accelerometer; and other necessary parts needed for correct performance. Program reads accelerometer value via ADC converter and indicates on one of 30 LEDs on the bars. There is simple lookup table implemented which corresponds to 1g(left) on first LED and 1g(right) on LED 30. The middle LED indicates the current G-force. Design can be improved by adding filtering from noise and vibrations. Continue reading

PIC18F4550 USB prototyping board

PIC18F4550 microcontroller has USB module built in. This allows using USB interface without additional interface chips and drivers. Evan has developed pretty simple PIC18F4550 prototyping board which is capable to download software via USB without need of other external programmer adapter.   Board can easily be adapted for various PIC USB interfacing projects such as HID or virtual COM port applications. PIC board is quite compact, but it has all pins available for interfacing. You may also want to grab a PIC USB Bootloader in order to test USB run.[via] Continue reading

Stepper motor controller on PIC

Stepper motors seems to be always interesting topic. And there is a lot of information about controlling them around the internet. Albert La also has been playing with steppers using PIC microcontroller. He constructed simple circuit with PIC16F84 microcontroller, TIP120 Darlington transistor pairs, and 4050 buffer IC for circuit protection. Wrote simple program which is able to run stepper motor with 7.5 degrees per step. This circuit can serve as stepper motor tester for instance picking right wiring, measuring revolution speed and so on. [via] Continue reading

Control stepper motor via USB

sixca has compiled nice example on how to control devices via USB interface. Simple solution is to take microcontroller with USB interface built in. PIC15F4550 has full speed USB interface with full speed capability. Microcontroller uses on chip USB driver which is pretty easy to program.   Firmware is programmed compiled with MPLAB C18 compiler tools. You may want to edit source in order to interface different devices like LCD, relays etc. PC software part is written with Delphi 6. It has three commands implemented: “Turn Left”, “Turn Right” and “Stop Motor”. This software can also be modified for your needs and recompiled with Delphi6 compiler. Continue reading

AVR tiny code lock

Code lock is used for access control. User has to enter 1 to 4 digit code (in free version) to unlock the door or several doors if needed. Code is entered via button keypad matrix. Optionally there can be LCD module connected.   For free light version author provides project schematic and hex file. If you see this project valuable you may purchase preprogrammed Attiny2313 with more codes and professionally made PCB. Check out the site for more interesting information including programmer, GSM alarm. Some of pages are in Slovakian language. Continue reading