Hello everyone,
The situation
My motorcycle is missing a tachometer (never had one), so I build one using an Arduino Nano. It reads the rpm from the diagnostics port and this part is already working. You can read the story on https://forum.arduino.cc/index.php?topic=236092.msg4513509#msg4513509 .
The problem
The tachometer only works when the motorcycle is idling or when the rpm is low. When revving the connection is lost. I need a circuit that filters the 12V power supply from the motorcycle.
My solution so far
I designed the following circuit:
The part on the right is already working (at least for low rpm). The K-line connects to the diagnostics port.
The part on the left (of the green line) is what I added to improve the situation.
It includes a TVS diode to get rid of voltage spikes above 16V. (continuous voltage could be 14.5 V during operation)
The RC filter has a low R to prevent a large voltage drop.
The RC filter has a low-pass cutoff frequency of 16 Hz. (which seems to work, but I was just guessing here)
This filter seems to work (also for higher rpm), at least when the motorcycle is standing still in my garage.
My question
Although it seems to work, I was just guessing what to build. I also tried a linear regulator, which did not work. Also the circuit is still on a breadboard and not ready for a field test. I would like to hear your expert opinions before I start soldering.
Is this a decent solution? Are there things that could be improved?
A consideration: Currently, the circuit uses only 24 mA @12 V, but later I would like to add a buck converter before the regulator so that I can add a bright display and maybe a GPS module. I am thinking 0,5 A @ 12 V.
The situation
My motorcycle is missing a tachometer (never had one), so I build one using an Arduino Nano. It reads the rpm from the diagnostics port and this part is already working. You can read the story on https://forum.arduino.cc/index.php?topic=236092.msg4513509#msg4513509 .
The problem
The tachometer only works when the motorcycle is idling or when the rpm is low. When revving the connection is lost. I need a circuit that filters the 12V power supply from the motorcycle.
My solution so far
I designed the following circuit:
The part on the right is already working (at least for low rpm). The K-line connects to the diagnostics port.
The part on the left (of the green line) is what I added to improve the situation.
It includes a TVS diode to get rid of voltage spikes above 16V. (continuous voltage could be 14.5 V during operation)
The RC filter has a low R to prevent a large voltage drop.
The RC filter has a low-pass cutoff frequency of 16 Hz. (which seems to work, but I was just guessing here)
This filter seems to work (also for higher rpm), at least when the motorcycle is standing still in my garage.
My question
Although it seems to work, I was just guessing what to build. I also tried a linear regulator, which did not work. Also the circuit is still on a breadboard and not ready for a field test. I would like to hear your expert opinions before I start soldering.
Is this a decent solution? Are there things that could be improved?
A consideration: Currently, the circuit uses only 24 mA @12 V, but later I would like to add a buck converter before the regulator so that I can add a bright display and maybe a GPS module. I am thinking 0,5 A @ 12 V.
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