The Lathe/Mill tachometer allows for display of the rotational speed of a Lathe or Milling machine. The unit can work with several different types of sensors, including hall-effect sensors, inductive sensors and photo-electric sensors. The firmware allows gear-train compensation where the sensor cannot be connected to the output shaft, as well as allowing for sensors with a different number of pulses per revolution.
The firmware is programmed directly in assembler allowing for pulse frequencies approaching 80KHz. The display is a 5-digit LED display that can indicate speeds up to 99,999RPM.
The tachometer is designed for a power supply input of 9V-36V DC or 9V to 24V AC.
Sensor
The sensor can be a pull-up or pull-down sensor (commonly sold as PNP or NPN) and can be powered by the rectified 5V supply, or by the unrectified power supply. Selection of pull-up or pull-down is done by a jumper on the board.
Parameters
The parameters are input directly by switching the device to setup mode using the switch on the PCB and resetting the power. Once in setup mode, the 4-switches on the PCB are used for setting up the sensor and gear compensation parameters. There is also a facility to compensate for oscillator drift of the micro-controller.
Power supply
A power supply with an output in the 9V to 36V DC range needs to be provided by the purchaser/builder. The power supply needs to be able to provide around 2W at the selected voltage. As the voltage regulator on the board is a switching regulator (buck), the efficiency is high, and the power requirmement are almost constant.
