Well Mr. Curtis is almost finished with my board and I was pre-pondering how I'll apply this to my 2001 V6 Tacoma that's getting the HE351VE treatment. I was toying with the idea of using an OBD-UART serial adapter to take in engine load and RPM from the factory ECU and using those values to spit out a target compressor speed based on values in a 2D lookup table.
Any thoughts if this would work or not? Dumb question? I'm an ME but control systems is not an area of expertise of mine.
P.S. here's the adapter I was looking at
http://freematics.com/store/index.php?route=product/product&product_id=30
That adapter didn't work for me and my 2000 dodge. You need to verify what OBD protocol is being used on your truck.
I am working through using a ELM327 obd adapter and piping that info into my setup using serial.println() and serial.read functions.
Alright, I ordered this:
I should be able to make a multi-dimensional array to have a target shaft speed based on load and engine RPM.
(http://i131.photobucket.com/albums/p310/anothernord/Freematics_OBD_Data_Logger_Kit3.jpg) (http://s131.photobucket.com/user/anothernord/media/Freematics_OBD_Data_Logger_Kit3.jpg.html)
I really hope your truck is compatible with the 2 protocols that thing supports. I was pretty unhappy with mine. It didn't work worth a darn.
I would recommend tapping into the TPS sensor and doing your own calculations, though I will say you'll inevitably learn a lot by doing things another way, whether they're successful or not.. I'm going to try to hack a Garmin GPS to do my display... dont know if it'll work though
So it turns out the order didn't go through, which is really great because I just found that it doesn't support my Toyota's ISO 9141-2 protocol. Whew!
I suppose tapping the TPS and RPM signals are the best way option otherwise.
Thats some good luck!
You might be able to tap into the tach signal to get your RPM, and into the TPS wire directly for TPS sensing... That's how I did it on my truck and it works pretty good
Yeah TPS should be easy since it's just 0-5V already. analogRead should work fine. The tach signal seems trickier. I'm guessing it's a square wave from the ECU with 12v amplitude, so a transition to convert to 5V will be necessary. I suppose you have code for your tach reading? I'd be interested to see it.
I read the tach with a pin falling interrupt on pin 2.. interrupt increments a number, then whenever I recalculate my inputs I see how many times it fired..
On my truck, the tach signal from the ECU to the dash is ALREADY a 5V square wave (very very short duty though). I will post up code once I smooth out a few more hiccups I'm working on