I-Button electronic door lock

Electronic lock developed by Dim uses the Dallas i-Button DS1990 data carrier. I-Button transfers identification data via 1-wire protocol which only requires single data lead and ground. It carries unique 64-bit registration number which can serve as a key to unlock an electric door lock.   Control circuit is based on Atmega32 microcontroller which stores up to 20 key data plus master key in EEPROM memory and also assigns a person name to key ID which can be displayed on LCD while key is activated. Electronic lock can be configured via RS232 interface. Keys and persons can be assigned using PC windows screens. Project files are available in downloads page. It is hard to say how this is convenient to use such key – maybe in some specific areas like event tracking, inventory marking. Of course it is probably more convenient to use RFID. Continue reading

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