I am wanting to make an rpm gauge for my jet ski. My plan was to place a plastic tab that I 3D print on the rear fly wheel (flywheel circled in picture below). The tab would go through an IR sensor and an Arduino would be able to count the amount of revolutions and then convert it to an RPM. My problem is that the fly wheel is in the bilge area that usually has water in it. Its not necessarily submerged but will definitely be splashed with water while the jet ski is moving. I have not been able to find a waterproof IR sensor. Do you know of any out there? Or do you know of a different waterproof sensor I could use for this application? I will have the Arduino in a waterproof case. I just need the sensor to be waterproof as that will be exposed to water. Any help would be greatly appreciated.
Water absorbs IR light. Maybe a Hall effect magnetic sensor with a small magnet (or more than one) on the flywheel would work better. Magnetic sensors are often used for crank and cam position sensing in automotive environments.
Have you looked at a magnetic sensor such as a reed switch? Check this link: Arduino RPM Reed Switch - Project Guidance - Arduino Forum
gilshultz:
Have you looked at a magnetic sensor such as a reed switch? Check this link: Arduino RPM Reed Switch - Project Guidance - Arduino Forum
groundFungus:
Magnetic sensors are often used for crank and cam position sensing in automotive environments.
I thought about a magnetic sensor. However, I was worried about switch bounce. The RPMS get up to about 7500 which is 125 revolutions per second. I was worried with a reed switch, the switch bounce would give inaccurate readings at high rpms.
Why would you use a relatively fragile mechanical switch with its inherent bounce when Hall effect sensors are so much better and they are cheap. Besides the reed switch will not be fast enough to work at high RPM.
Hall effect switches do not bounce. They are solid state so have no moving parts to bounce, unlike a mechanical switch. And they are fast and many have built in hysteresis.
groundFungus:
Hall effect switches do not bounce. They are solid state so have no moving parts to bounce, unlike a mechanical switch. And they are fast and many have built in hysteresis.
I guess I never fully understood how a hall effect switch worked. That would be a better route for sure. Would these sensors be waterproof? I am having trouble finding a sensor that would be waterproof for my application. I could place a magnet in the tab on the flywheel to trigger the sensor.
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