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Voice-operated and proximity lift controls One big problem with lifts is that you usually have to press a button to select which floor you want to go to. And with everyone pressing these buttons, there is the possibility of spreading disease. So I came up with these voice-operated controls for the service lift at my workplace. It takes a voice command from people inside the lift and converts them into electrical signals which operate solenoids to press the lift buttons. To call the lift, one or two proximity sensors are provided at each floor, for up & down. All you need to do is wave your hand near the sensor to call the lift. This project can handle other voice commands, such as opening and closing doors, controlling a fan or triggering an alarm. A laptop with an Intel Core i3 processor handles the voice recognition, passing commands to the Arduino via a USB connection. Within the lift, nine solenoid thimbles placed on the control switch touchpad operate the buttons. This is attached to the lift using a 160mm x 10mm wire frame on top of the lift command keypad. A technician from 54 Silicon Chip the turbine maintenance department made the small cage-like solenoid holding pads which push the switch pads. After receiving a command, the machine speaks out the intercepted command and then executes the command to actuate the right solenoid to press the button. This is handled by the Arduino triggering a transistor to drive the solenoid coil using one of its digital outputs. Commands are supported in English and Hindi, including “first floor”/“ek number”, “second floor”/“do number”, “third floor”/“teen number” and “fourth floor”/“char number”. If the command is not understood, it will ask for you to repeat it. Arduino digital outputs D5-D13 provide the following functions, in order: fan stop, fan start, alarm, door open, door close, first floor, second floor, third floor and fourth floor. The extended commands “pankha chalu”/“fan on”, “pankha band”/“fan on”, “darvaja kholo”/“door open”, “darvaja band”/“door closed”, “ghanti”/“alarm” are used for the other commands on digital outputs D5-D9. Australia’s electronics magazine The software running on the PC was developed using Python and Google Speech. Its source code (plus the Arduino program that it controls) is available at siliconchip.com.au/ Shop/6/5780 The solenoids are powered from a 5V 2A plugpack, while the Arduino is powered from the laptop’s USB 5V supply. As the solenoid driver transistors are on the low side, 12V or 24V solenoids could also be used with a matching power supply. Each solenoid has a diode, which is normally reverse-biased, connected across it to absorb the back-EMF spike when it switches off. The circuit below is much simpler, providing the interface to call the lift. The ATmega328 is programmed using the Arduino IDE and it periodically sends pulses to the two ultrasonic distance sensors and ‘listens’ for an echo. If it senses an object near one of the sensors (within about 22cm), it triggers the associated solenoid, in much the same manner as the in-lift circuit shown at right. Bera Somnath, Vindhyanagar, India. ($150) siliconchip.com.au Circuit Ideas Wanted siliconchip.com.au Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia’s electronics magazine November 2021  55