digital steam engine indicator

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

Post by Steam Captain » Thu Feb 20, 2020 9:31 pm

So,

The separate calculation of the medium pressure is done.
The calculation of the power is done.
Everything is prepared so far for the addition of the display.

Now, my todo list has changed a little:

The metric/imperial options will definitely be implemented. It's too easy not to do. It is just using different constants.
I definitely decided for a TDC sensor subroutine, as it will make turning the crankshaft into position obsolete AND will add the important possibility of a self-correcting algorithm.

The input options so far contain the 4 variables: stroke, bore, con rod length and single or double acting. These will be the only variables asked for by the program.

My step now is to bring it to the physical world and attach it to a fridge compressor, because I need readings with real pressure values under real life conditions. Until now, I helped myself out with virtual pressure readings. I do suspect, that the 1-2ms response delay of the pressure sensors I've found will be very limiting for the rpm.
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Re: digital steam engine indicator

Post by Steam Captain » Thu Mar 19, 2020 8:38 am

Soo, many things happened.

I have figured out how to draw stuff on an Arduino screen and this is the first try I got:

Image

It isn't visible on the photo, but the green is like REAL green. Bright as can be. Right out of a neon pencil.
I am going to change the display color to a warm one like orange or maybe I am going to use a black background with everything drawn in warm colors like orange or red, since it is more pleasant for the eyes. The display is a 2.4" tft screen. Maybe I opt for an a little bigger screen like 3.5", but this is already ok for testing. The only worries I have is, that the 2.4" screen does get a little small if I want to display all the numbers AND the pV-diagram. And I want.

So, let's just see. I am currently working on passing a financial bottleneck and get my tools into this city and then, I can continue with the project. I did for example find out, that there are encoders with z-channels (one impule per rotation). This means I wouldn't need any additional hall sensor shenanigans.
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Re: digital steam engine indicator

Post by TahoeSteam » Fri Mar 20, 2020 3:42 am

You're making some real progress! I'm excited to see your final product and how it works. Nice work!

Please stay safe.
~Wesley Harcourt~
Check out the steamboat and steamSHIP videos on my YouTube page: https://www.youtube.com/c/wesleyharcourtsteamandmore
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Re: digital steam engine indicator

Post by Steam Captain » Wed May 20, 2020 4:01 pm

As a major challenge in life has made me lose almost al my belongings a couple of months ago, including my workshop, I have to start anew.
I now have a garage I am equipping with new tools and everything to continue with my hobby. The good thing is, that I now can have a real workshop with ground-level accessibility (It WAS tricky having a workshop in a 8m² tenement building cellar.

Since the steam virus knows no cure, I'm still planning on building the opposed-piston steam engine project, the digital steam indicator and a gasoline-fueled monotube boiler.

This project hasn't been affected so much, because all the stuff I did here was after the loss.
As an update, a fridge compressor is lying in my garage workshop waiting for a simple slide valve arrangement to be screwed on its cylinder head. Since I have to completely equip a new workshop, I didn't want to wait so long to build the steam engine to test the indicator. Technically, I just need some mechanical contraption with an axis to strap the decoder on and a displacement space with a fluctuating pressure to test the indicator.

Until now, I've used a decoder without a z-channel. This is a channel, that gives off one pulse per rotation. This means I wouldn't even need an external rpm counter and just use the z-channel. There is the amazing advantage that one can use this signal to eliminate erroneous ping countings adding up over many rotations, simply by starting the program loop whenever the z-channel pings. It really makes things MASSIVELY easier.
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Re: digital steam engine indicator

Post by Steam Captain » Fri Jul 17, 2020 10:29 pm

Sooooo.

I think I've finally succeeded.

The programs work and I am now just streamlining them to make them as usable as possible for a wide variety of uses. A new pressure transducer-rotary encoder set is on the way and while they are coming, I am going to write a downloadable pdf manual with all the needed intel in it. I didn't figure out a way yet to upload files to the internet, but I guess the worst case would be to directly send it around via email.

The mechanical linking of the pressure transducer and rotary encoder to the engine is something I naturally can not include into the manual due to the very wide variety of steam engines we're using. But let's just remark having small condensate cocks on the cylinders would be the easiest method of attaching something to screw the pressure transducer on.

Anyways, I'll just fiddle with the new sensors and then upload everything.
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Re: digital steam engine indicator

Post by fredrosse » Sat Jul 18, 2020 11:16 am

Great to hear of your progress, and I am sure many of us are anticipating the working P-V display system, as well as a computerized nearly instantaneous display of engine “indicated Power”. Thanks so much for your efforts here.
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Re: digital steam engine indicator

Post by RNoe » Sat Jul 18, 2020 3:52 pm

I dream of an electronic steam cylinder Indicator system that plugs into (or Bluetooth connects) to our smart phones!
That would be revolutionary.
...all puns intended...
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Re: digital steam engine indicator

Post by Steam Captain » Wed Jul 22, 2020 6:30 pm

Yes, I think it can be extremely useful to be able to see a real rime P-V-diagram to learn how the engine is fairing and to see how the conditions inside the cylinder are changing along a revolution.

I am actually already thinking about a later upgrade to save the data of an entire trip onto a SD card or something like this. That way, it would almost be like a black box with the rpm and the indicator diagram changes saved over time.

Plugging it into a smartphone, hmmh? I could have done that from the beginning on. A separate display wouldn't have been needed that way. But to be honest, I am not such a big fan of cell phones (no big reason for it, just a sentiment). And I thought it might be more handy to have a display as an integrated part of the steam engine indicator. No smartphone dependency or wifi/bluetooth hassle. BUT technically, sending and plotting data to a smartphone shouldn't be that hard to program.

I am now streamlining and error-testing the code, which displays real time rpm, pmax, pmin, indicated power and the diagram itself. I got a little annoyed with the keypad subroutine and left it out for now, which won't be a real problem for its use anyways because the keypad would only be used to input the piston diameter, stroke and con rod length, it just needs to be entered once ore very rarely. But the 2nd step will be for me to make it run with the keypad and to implement a means to log the data onto an SD card for later use on a PC. It is very analytical and might not be so interesting for some, but since it isn't much additional work to do, I thought of just adding it later on. So, why not.
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