Tuesday, April 14, 2009

Engine telemetry

Engine monitor

Here you see the PIC16F88 microchip based engine telemetry package I've been working on for a while, up and running.

It now has both the engine rev counter and one pressure sensor implemented. Those numbers you see are for real.

The only issue is that the revs are showing at exactly half of what they should be, as I mounted the rev counter sensor on the cam shaft which runs at half the speed of the main shaft. This is easily fixed though.

The green blobs, part of the digital readout on the left, show the status of the various sensors, where green is working ok, blue indicates a sensor fault and red shows an alarm state (the alarms are still to be implemented).

I've also posted pictures on flickr of the other screen shots I took, showing the full cycle from startup to shutdown and the console view which hides the detail.

There are additional pressure sensors to be fitted to the system, the most difficult part of this being the physical connection of these to the engine. Everything else is taken care of.

I opted to show separate charts for pressures and temperatures, and to super-impose the revs onto both charts to make them easier to read.

As it happens, the gauges in the boat's engine room compare closely with my rev counter and the electronic oil pressure transmitter, but the rev counter and oil pressure gauges in the wheelhouse are a little off.

There is no doubt in my mind that the data now available from every subsequent engine run will prove invaluable in the future. For example, comparisons before and after an oil change, and determining if things are ok after working on the boat's systems.


  1. Think of the fuel economy of a well run engine! great job Tim

  2. Anonymous2:31 AM

    This is looking really cool. I'm excited to see all this coming together. Thanks for sharing it Tim!

    Interesting that the oil pressure seems to drop so fast when the RPM drops below 200rpm -- you lost 1/2 bar just like that.

    Also interesting that the salt out temperature climbs after the engine shuts down. I guess the circulating pump stops then too, and we're seeing latent heat in the exchanger heat the last bit of water.

  3. Hi Rob

    Thanks for that.



  4. Hi Anonymous

    I'll post more traces as they develop. Hopefully with Lady Jane under way sometime soon:)

    That drop in revs may have been more than it looks in the picture, as I dropped the revs and put the vessel in gear momentarily.

    But you are right, the oil pressure sure does drop fast, conversely, raising the revs to 360 rpm does not seem to increase the oil pressure, as I would have expected it to.

    I suspect to some extent it's because the salt out pipework is no longer being cooled, so gains the heat from it's immediate environment pretty quickly.