digital steam engine indicator

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Mike Rometer
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Re: digital steam engine indicator

Post by Mike Rometer » Fri Mar 29, 2019 9:43 pm

Basicaly, the ones I've seen are a ring round the crank with 36 notches the one at TDC is larger as calibrator. The notches are read by a small coil with a magnetic core. Don't ask about the attatched electronics, that's beyond my ken, but I believe they can calculate the crank position to better than 0.1 of a degree, and with other sensors on the engine set the ignition to the optimum for the prevailing conditions, speed, load, etc.

The reluctor ring is usually fitted to the flywheel, or occasionally the front pulley.

Understand that I have been retired for more than 20 years and for the last 5 of working was no longer involved with such things, so methods will undoubtedly have changed/improved, but a little research should turn something usable up.
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Lopez Mike
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Re: digital steam engine indicator

Post by Lopez Mike » Sat Mar 30, 2019 2:04 am

There is just such a thing on the front of many car engines. A ring with all of the notches and a sensor that tells the car's black box when to send juice to each spark plug and when to activate the fuel injectors. You local wrecking yard can be your friend.
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marinesteam
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Re: digital steam engine indicator

Post by marinesteam » Mon Apr 01, 2019 2:02 am

Mike Rometer wrote:
Fri Mar 29, 2019 9:43 pm
Basicaly, the ones I've seen are a ring round the crank with 36 notches the one at TDC is larger as calibrator. The notches are read by a small coil with a magnetic core. Don't ask about the attatched electronics, that's beyond my ken, but I believe they can calculate the crank position to better than 0.1 of a degree, and with other sensors on the engine set the ignition to the optimum for the prevailing conditions, speed, load, etc.

The reluctor ring is usually fitted to the flywheel, or occasionally the front pulley.

Understand that I have been retired for more than 20 years and for the last 5 of working was no longer involved with such things, so methods will undoubtedly have changed/improved, but a little research should turn something usable up.
Prior to modern fast electronics, less resolution was wanted due to the time needed to acquire & process the input. At a constant speed it is possible to calculate a position accurately but you can never have a known position better than 10 degrees with the example given. When sensor and processor speeds weren't what they are now an analog device called a resolver was often used to determine position as digital devices (encoders ) were too slow. Now, modern encoders can be used at quite high speeds without issue with sub degree accuracy at very low cost. No need to reinvent the wheel as you can get an appropriate encoder for arduino for about $40 usd, like this one:
https://www.kr4.us/rotary-encoder-200-p ... gJHBvD_BwE.

Cheers

Ken
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Ramón
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Re: digital steam engine indicator

Post by Ramón » Wed May 08, 2019 3:16 pm

Exactly. I think an encoder would do the trick. I am still not sure how an reluctor works, but if it is the ignition timer thing I had in my car, I suspect it would be usable for rpm messuring, but not for a good diagram - at least as far as I understand magnetic reluctors. But rotary encoders seem to be a good choice, as they are cheap and can messure even more points per rotation than needed after all.

I guess I confuse a reluctor with a distributor - never mind.
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