Basic2 stamp as a microcontroller for a turbine engine ECU

R U Sure

Hi, I am probably the newest newbie. I am not proficiant or knowledgeable about electronics or programing but have searched and searched for something to fit my application and every one makes something near what I need but not quite wat I need. I actually stumbled onto this Parallax Basic2 stamp thing while researching small RC turbine engine ECU projects. I bought it on an impulse and having gone to chapter 2 tonight I think it might work but would like to get some opinions from the experinced.
I have a small electroinc (EECU) controlled 100 SHP turbine engine that used an 1980 era IC main board made to MIL Spec standards for ground staring aircraft. It was obviously too complex and heavy for me to use for my needs and couldn't be modified (by me anyway) due to its being incased in epoxy.
What I need to do is create a full control start and run system to run on a stand to operate in a constent speed application. It should operate at·idle (Say 70% RPM) and·normal operating speed of·100% (50300)·rpm. I have already purchased a Govenors of America PWM engine govenor (ESD2100) which I expect to power the HP fuel pump to maintain engine speed with instructions via feedback from the Basic2 stamp.

What I want to know iif the Basic2 stamp is capable of is:
Sense monoplole speed sensor
Sense oil pressure from pressure switch
Confirm 0, if no speed or pressure is replied (confirm engine is not already running)then to engage starter motor, once starter spins turbine to 30% RPM to start fuel sequence, start igniter circuit, open fuel solenoid, verify compressor pressure (if less than .5 psi then start shutdown shut off fuel ). After sustained ignite and confirmed acceleration shut down stater and commit High Pressure pump current via ESD2100 PWM speed controller to maitain ground idle or operating RPM.

The order and comands I need it to do still need to be determined but I am just wondering if I am toying with the wrong item here or if its even close. Since I am just starting I have no idea how this tiny circuitry interfaces with the sensor used on the engine but I have a feeling there is a way. Gotta start somewhere

Thank you for any imput you have to offer,
Jim

QuattroRS4

The stamp is capable of doing what you require - sequentially or looping - but you will most likely require some third party I.C's/devices to convert your measurements (pressure/speed etc) into 'stamp' meaningful data/signals.

If you want continuous monitoring and control can I suggest the 'Propeller' - this is a more than capable multitasking microprocessor ..

Regards,
John Twomey

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'Necessity is the mother of invention'

LoopyByteloose

Well, you leave us to a lot of guessing about how your sensors would interface with 16 pins of +5/0 TTL or CMOS logic.

For instance, the Sense oil pressure switch. Is that merely on and off? Or, does it measure levels of pressure? Is the output +5 volts? And does the switch bounce electically? A lot can be done with Opto-isolation on the inputs to the BasicStamp to make reponses cleaner, but timing is usually limited to about 2 microseconds. Is that fast enough?

The 'Monoplole speed sensor' is a bit unclear. Are you referring to a magnet that triggers a Hall-effect sensor? Not all Hall-effect sensors are the same. Do you have to provide the right one or is it included? If this needs to be closely watched, you might want one microcontroller just monitoring RPM full-time and sending along status to a second device for controling the engine's operating conditions. It is a critical process that may be too much for multi-tasking.

Over all, the question of response time from the BasicStamp may lead you to the faster SX-28 and it's version of Basic, called SX/B. If you need a lot of I/O or independent multi-use timers for the RPM detection, an SX-48 may be better.

If you have a complete, yet simple State Machine plan for operation; that would be a great help. No one really wants to say that it can easily be done and find out that you blew up the turbine because something did not respond as expected.

If the old board was potted in epoxy, there is a good likelyhood that it will adapt to a much smaller microcontroller. But how small remains to be understood. Also, how much of the sensor support circuitry is under that epoxy?

You might consider using the BasicStamp PLC to provide complete isolation for controling the start fuel sequense, the start igniter circuit, the open fuel solenoid, the verify compessor pressure, and so on. Do you need more than 16 I/O pins? How many In and how many Out?

The Propeller is much faster, does 8 tasks in parallel processing, and has 32 i/0 pins of which 28 are easily available.· Each task is on it's own COG and one COG could manage the RPM sensing full-time while another 7 remain to be used for startup, regular operation, and shut-down.· It certainly would be the more elegant solution.· It might even provide you with video diagnostic output.

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PLEASE CONSIDER the following:

Do you want a quickly operational black box solution or the knowledge included therein?······

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 3/11/2008 11:41:11 AM GMT

Bruce Bates

Jim -

At first glance, I'd say you might have a winner using a PBASIC Stamp. Take what I say, as you will. I spent some time researching your questions, but I'm sure there is more to be done.

If you haven't done some thinking on how much you are willing to spend on doing this interfacing, I would do so soon. You're talking a few bucks here, and I wouldn't want to see you moving forward with any solution which ends up being more costly then you have budgeted. As you will see shortly, a PC will be required for part of this system, and using the PC for all of the monitoring and adjustments, may be the better way to go with the use of a separate PC board to interface with these sensors.

Now a couple of questions:

1. Are you aware that there needs to be manufacturer supplied, Windows software loaded into a PC to adjust, calibrate, and interface with the ESD2100 PWM controller? This software sets parameters within the controller and when the "programming" of the controller is finished, the documentation which I found says something like "Once programmed, the cable to the controller must be disconnected" (emphasis theirs).

One would have to presume this would apply to any device connected to the serial data port on the controller. This would preclude having the Stamp interface with this controller when it is running, if that's what you'd planned. Even in a static circumstance, there are way too many parameters to be easily handled by a PBASIC Stamp, which is a highly versatile, but memory limited microcontroller (as many are).

If this rains on your parade, I'm sorry, but that's how I read the ESD-21xx brochure which I downloaded from the Governors of America (GOA) web site. If you'd like a copy of that document, just say so, and I'll upload it to a message here, so that you can download it to your computer. If you'd prefer, I can just provide a link to the appropriate are on the GOA web site.

Presuming that's not a problem, let us continue:

2. Do any of the operations you have listed need to occur simultaneously (at exactly the same time). I'm not speaking concurrently (during a given time period), as this is easily done. The Stamp is single-threaded, which means it can only do one thing at a time. It can do many things during a given time period however. Parallax does have other microcontrollers, other than the Stamp, which may be better suited to the tasks at hand.

3. Before committing to any microcontroller (Stamp included) you would need to know what kind of interface each of these sensors has. In other words, you will need the technical data sheets which describe these sensors in some detail, as well as how the can be interfaced. You can leave the details to "us", but the information needs to be made available either through a web link to this information, or by providing the actual data sheets by means of uploading them to this Stamp Forum.

A number of the sensors appear to need electrical compatibility interfaces. This may be as simple as using a resistor to affect this compatibility, or it may need to be something a bit more complex. None of these compatibility efforts amount to "rocket science".

4. The "1980 era IC main board" may prove to be a bit of a problem, but you will face that with any microcontroller you might use to interface with it. IF there is ANY documentation available for it, that would be great. Otherwise some testing of the unit may need to be done, both statically, and dynamically. Interfacing in and of itself isn't the real problem, it's just how it's done that needs to be addressed. Older boards need slightly different interfacing, so one needs to be careful in how the interface is constructed. This is probably not as large a task as it may sound!

5. I suspect there may need to be an "adapter" made to handle the high RPM. If this turns out to be the case, you may lose some accuracy by doing so, but I'm not sure that a loss of some RPM accuracy at 50,000+ RPM is going to make all that much difference, but you would be the better judge of that. Certainly, if you end up using a Stamp, one of the faster models would be more appropriate.

6. In addition to the interfaces above, it may be necessary to implement some relays. The Stamp I/O ports (how it communicates with the outside world) can only handle so much current (amperage), so relays are employed to carry this current. Again it just needs to be addressed.

7. It appears you may need the timing services of an electronic clock (another IC). Probably one with an elapsed time feature would be the best bet. Many of these are available, and implementing them is not a major project. Let me know if you need help in this area.

8. Since most of the PBASIC Stamps only have 16 I/O ports, there may be a need to expand them, but that's a rather trivial issue. The IC's used are not expensive either.

That covers a good deal of it, but I'm sure there is LOTS more to be considered.

Regards,

Bruce Bates

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Programming can't be all that difficult, it's nothing but 1's and 0's

R U Sure

Wow! I didn't really expect this fast of a responce and support for my project. I would like to thank you John, Krammer and especially Bruce for the indepth consideration.

I haven't given consideration to cost as I have to consider these as they are learned but I expect to learn new skills untill I reach the "brick wall" of either cash or ability.

Bruce, I have read the PDF manual (same as paper one included with unit) and couldn't find any information regarding programming it or using a PC to make changes to it. I assumed it was a closed system that simply gets its instructions from speed sensor frequency and adjusted by pots. I bought it 3 years ago for $220 and now they are only $120 from distributors. I may or may not use it or need it by the time I am through.

A lot of information I need to gather will require me to obtain and learn to use an oscilloscope from what I gather. This will probably be my next Parallax purchase.
Also have been considering the other other Parallax project units as well (propellor) etc

I have the government manuals for this unit but don't have any web storage from which to FTP them for sharing and both are about 4MB each. Can these be attached to the forum as files? Would it be rude to attach them? Other wise I can snip images and attach those.

Thanks for all the information much of which I still must absorb. Looks like I am on my way to a new form of sublimation

Jim

R U Sure

Here are a few pictures of basic block structure and text of the manual description.
This of course was a generator and many circuits and much switching is not going to be used. The actual schematics are very complex but will snip images if anyone is really interested in looking at them. Of course my intention is to simplify more than anything and this can be done by manually operating the turbine using simple circuits and manual observation and adjustments using standard interface devices which will be used as well even if this project is a success.

I will most likely go through the complete basic project book before making too many plans
Thanks for the imput.

Jim



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