Motorcycle Universal Gear Indicatorauthor: Vassilis Papanikolaou
This is a new design for a universal gear indicator that can be fitted to any motorcycle as an aftermarket accessory. Its main advantage is that its operation depends entirely on the gear shift lever movement, instead of connecting to speedometer and tachometer sensors (found in expensive commercial devices), which are rarely available in older motorcycles. It consists of a main circuit including a 7‑segment LED indicator, two Hall sensors that are attached to the motorcycle frame, and a small magnet placed on the gear shift lever.
The source code is written in AVR-GCC (WinAVR) and can be programmed with the default fuses using an AVR programmer (default : ATTINY25 microcontroller and USBTiny programmer). Moreover, the constant TOP_GEAR 5 should be changed to 6 for six-gear motorbikes.
The suggested implementation for the main circuit is a small size, double-sided PCB, with SMD packages for the microcontroller and the decoder ICs. The 7-segment LED is placed in a secondary PCB, connected vertically to the main one in a modular fashion (see pictures). Two PCBs for different Kingbright LED footprints (red and blue) are also provided.
In the current design, when the neutral switch is
open (there is a gear on), there appears to be a very small current (<
0.5 mA) sinking through R3, due to the voltage difference between the
neutral switch connection (TO_POWER-4) and the microcontroller. If the
neutral indicator is of LED type (not a resistor bulb), there is a
possibility that it stays dimmed, instead of being completely off. In
that case, a small switching diode (1N4148) can nicely replace R3 (on
the same PCB) in order to block this small incoming current when the
neutral switch is open, as shown in the figure below :
For a better insight in the above issue, the following script can be imported in Paul Falstad's excellent circuit simulator
$ 1 5.0E-6 10.20027730826997 62 5.0 50
Contributed by Brett Walach
A successful circuit build will do a self-test when connected solely to 12V power (pins TO_POWER_1 and TO_POWER_2), by cycling through all digits on the 7-segment display (see video below). After the self-test, the current gear will be shown and can be changed by the shift lever movement. Note that a gear is changed when the magnet's south pole is drawn away from the sensor (north pole will not work). Moreover, if a neutral gear is detected (from the neutral switch connected to TO_POWER_4), the display resets to zero (also acting as a self-calibrating feature if anything goes wrong). Finally, when the power is turned off, the last shown gear is stored in the MCU's flash EEPROM and restored when the device is turned on again.
The following video shows the initialization procedure of the gear indicator :
The following photos show the construction of the 4-wire sensors cable that is plugged to the TO_SENSORS connector. The visible sensor pin parts should be covered with plastic lacquer for protection as well.
After putting it all together the circuit is now operative and ready to be installed on the motorcycle. A video showing a simulation of gear shifting (by hand) is available below :
Here are some photos and videos from the installation on my Suzuki Intruder VS400 :
Gear shifting by hand
Real gear shifting with engine on
Storing last gear in EEPROM
Thanks for reading !
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