PLCs/PICs (computer interfacing and controlling)

[Richard OConnell]

Those Arduino boards look pretty nice. I couldnt find one that would be suitable for reading a tach drive which would use impulses per second. Any of them, in theory, could relay that using the usb hookup, but if the board's latency cant keep up with the speed of the impulses, it wouldn't be of any use. I 'm going to try to find out more from their community.

[turborico]

I've seen a few references out there of people using Arduino's to get tach readings with success, even in the 100K range. I'll post it up if I find it.

[ernie wrenn]

I found a few controllers on e-bay..take a look :

310153618523

380365839640

Any ideas..

ernie

[wolfdragon]

Ernie,

Since you are running commercial jet engines, the first one (Dakota Digital DSL-2) would probably be the easiest to use. I don't know your engine by heart, but on most jet engines, the pickup for the tach is a spinning gear and a hall effect sensor, which is what this kit is. You would have to take a look and see what you have available for a mounting location but that DSL-2 is designed to look at gear teeth as they go whizzing by and counting them as they come.

[stimps]

I been away a while, back to say I have had some success. Ive been biulding my engine when I get time, and Currently waitting for my lathe to get fixed so not alot been happenign there, other than welding some combuster parts. ALTHO...I have changed how I will biuld the ECU
I went with arduino, and I have a mega with a LCD and a hash board for other bits needed.
So far, it has two thermocouple inputs, sending the data to the serial display on the PC, and the touchscreen inputs x and y co ords, to the screen, and will soon have the RPM sensing sorted, and Ive displayed a few items to the lcd. I also have the Pressure sensor and will interface that in soon.
It is a 240 x 320 colour display, touchscreen.
The plan is to have the ECU totally control the engine, and use the touchscreen to enter parameters as I "tune" it
such as fuel pump speed ramp up/down, warm up time, starter power, idle setting, etc. I am planning to use the fuel pump PWM to control the engine to desired speed setting, after the engine is sorted. Long way off yet.
'
cheers!

[Richard OConnell]

Very useful information. I'm going to start toying around with these systems very soon myself.

[stimps]

The unit so far....

[Richard OConnell]

Now thats spiffy I hope it works well for you.

[stimps]

Feel like im stealing a thread, but not keen enough to start a new thread about it yet, just thought id share the work so far.

m376.photobucket.com/albumview/albums/stimps/75a277d3.jpg.html?o=2

[ernie wrenn]

I am in..... How much?

ernie

[jnissen]

I helped my son sort out his tachometer for his jet build last year. I'm an electrical engineer and he is now a senior in high school. He is busy building a free power setup powered from his gas producer. Anyway one of the things he still has to do is update his tachometer code to now watch and monitor two turbine wheels as opposed to a single like last year.

He used an Arduino to do that task and it's got dedicated hardware inputs for monitoring signals like a tachometer. He used the INT0 input which is an edge triggered interrupt. When that input is sensed high the Arduino jumps to the interrupt handler code. The code essentially increments a count and then promptly returns to what it was doing before the interrupt. By quickly servicing the inteerupt the Arduino could easily handle 200K RPM or better. The hard part and the area I helped him sort out was finding a sensor that could reliably sense and fire the signal to the arduino. We eventually used a fiber optic sensor that was pointed at the compressor nut. Half the nut was painted gloss white and the other half was painted flat black. Most fiber sensors looked into would only handle about 65K RPM but we did find a sensor from Banner that would react fast enough and didn't cost to much. Think it supported 200K RPM but there was some available that could have supported to 500K RPM!

The electronics are not the limit here. The sensor is the limit. The Arduino, even the low frequency it runs at is still way faster than the mechanical turbocharger and could easily support readings up to several Mhz if needed.

The example code he used for the tach is on the yahoo DIYGasTurbine groups. Look in the files section under Nathan's code.

I see the progress that Stimps has made and applaud him on the effort. The Arduino is really a treat to program compared to some earlier variants. The interfacing to various bits is quite simple with all the libraries that are now available. LCD's, sensors, memories, etc... are all easily dropped into a design. I never even showed my son how to program the thing and he managed ot learn on his own how to get it going. It really is that easy and highly encourage anyone contemplating some control circuit to give it a try.