This module is connected to an automotive tacho / RPM signal, and provides a switched output that can be programmed to switched on from 100 to 10,000 RPM. It is typically used to control a shift light, however can be used for any applications that requires an RPM sensitive switch.
The module accepts DC square wave (hall effect) as well as inductive (AC sine wave) input signals, including direct connection to the ignition primary circuit (coil negative). The output is a negative side switch rated at a maximum 1 amp.
It includes detailed printed instructions, making installation very straight forward. A small case size (80x40x20mm) makes its easy to find a location to mount it. It can even be mounted directly to the wiring loom with cable ties.
- It receives either a DC square wave or AC voltage input signal – from the existing tacho signal, a hall or inductive sensor, or an ignition coil.
- The PPR (pulse per rev) of the input signal is configured using a rotary switch inside. This refers to how many pulses the signal has per revolution of the engine, and is typically 0.5 or 2. The module has options from 0.5 to 9.
- The desired switching RPM is selected via 2 more rotary switches, from 100 to 10,000RPM, in increments of 100 RPM.
- To ease installation, 2 onboard LEDs (INPUT and SHIFT) provide indication when a valid input signal is being received, and when the set RPM has been reached.
- When above the set RPM, the modules open collector output is connected to ground, turning on the shift light or other accessory.
- Hysteresis is provided to produce a smooth output and prevent rapid switching around the set point. The RPM must drop 2% below the set RPM before the output switches off. This can be disabled via solder pads on the PCB if desired.
- The input signal is filtered over 3 cycles to reduce noise and interference. This can also be disabled via solder pads on the PCB if desired.
- When using the 0.5 or 1 PPR options, a “multi-fire filter” is automatically applied to the input signal. This will ignore input pulses faster than approx 2.5ms / 400hz. This is useful for getting an RPM signal from engines that fire the coils multiple times per cycle at idle (eg. Ford Barra engines).
If you need to adjust your tacho signal to read correctly, check out the tacho signal converter.