Electronic variable vane control

Tymbrymi

03-25-2009, 08:17 AM #52

(03-23-2009, 10:10 AM)300SD81 I've been working on electronic controls for months. I remember posting some stuff at various forums, but I'm getting really close to getting my electronic actuator working now. The electronic actuator that came with my turbo had its own computer on board, and I spent about 2 months trying to interface with it before I decided to scrap it and design my own, so now I'm bypassing all the electronics and directly controlling the motor with my board, using a throttle position sensor off another car to sense vane position. Should have a working prototype within a couple weeks. I already have sensor boards and a USB interface built, so after I get the motor control system done, it'll be time to program the actual controller system...

Sweet!! Keep up the good work! Will you be posting schematics/code? If you aren't that's cool, just wanted to ask.

(03-23-2009, 10:41 AM)GREASY_BEAST Yeah, so I was a little arrogant/foolish about the software... but its no space shuttle either. Basically it all comes from tach sensor input, EGT input, boost input, rack position input, fuel pedal input, and spits out electrons to the actuator controls.

I wasn't trying to be an ass or anything, but I work with EE's that think software should ALWAYS take JUST an afternoon, and it gets tiring. So that was more of a knee jerk reaction Wink

Correct, that is the basic premise, but the devil is in the details, and if we're controlling the IP I will be paying a lot of attention to the details!

(03-23-2009, 10:41 AM)GREASY_BEAST The "actuator controls" consists of a relay or set of relays that can handle the current the actuator needs (or if you have electronic turbo controls, actuators plural).

Relays will not work. You need something that can do PWM signals at high current (2-3 amps I'm guessing), at a frequency of greater than 100Hz. Relays just don't cut it at that frequency. So power electronic circuits are required.

(03-23-2009, 10:41 AM)GREASY_BEAST It would be nice to also have ambient temperature input and engine temperature input as well to be able to do some cold start programming and additional engine protection. However, transforming the signals into a form that the board can interface with seems like the major challenge. Around May I'll have a 617 on an engine stand. I have a couple cruise servos kicking around. I'll have a board of some sort. Let the games begin.

IMO, sensors are easy. As 300SD81 and Gross Polluter have mentioned, there are already chips that will convert some of the tougher signals to something nice and easy for the microcontroller. I think the hardest part is the actuators and PID control of said actuators. Power electronics aren't *hard*, but they aren't trivial either.

(03-23-2009, 10:41 AM)GREASY_BEAST Oh, and BTW the MW IP for that engine is kaput so it will need new (larger) elements, thereby granting a means to test your theory about shadetree IP calibration

Let us know how it goes! Cool

(03-23-2009, 06:45 PM)300SD81 If you plan on using the board for EGT, might I suggest the MAX6675 (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3149 ) I'm using it for my EGT probe and its alot more accurate than using the microcontroller's AD inputs.

A friend used this chip on his senior design project, and it worked perfectly the first time and was super accurate. A lot more accurate than the ADC inputs is an understatement!!!

(03-23-2009, 06:45 PM)300SD81 As for my turbo project, I just finalized the design for the vane actuator circuit. I'm using a dsPIC33 microcontroller and H-bridge chip to drive the VNT's actuator motor directly, bypassing the built in computer.

VNT Actuator Board: http://img15.imageshack.us/img15/2223/vntboard.jpg

Nice work! Is that Orcad Layout? You have way more patience than I do!!!! I'm a big fan of Eagle... Much easier to use! Well, for me at least. Everyone here at work uses Orcad layout.

(03-23-2009, 06:45 PM)300SD81 As for circuit boards, the classic laser printer toner transfer method has worked for me for years now. 10 mil traces and 0.5mm pitch parts are possible if your good.

If you want to get yours fabricated we use 4pcb at work (we've done 16 layer, 260*C polyimide, 1 square foot sized boards, etc through them (not all at the same time though!) My next small project will use BatchPCB, which is perfect for small boards. You just can't be in a hurry.

http://www.batchpcb.com/
http://www.4pcb.com/index.php?load=content&page_id=134 (student special)
http://www.4pcb.com/index.php?load=content&page_id=130 ($33 pcb)

The $33 boards can be as large as 60 sqin, which is pretty big!

John Robbins
'05 E320 CDI - 118k - Faaaaaast!! Angel

'87 300TD - 317k - Cracked head... but an OM606 is on the way! Undecided

'79 300SD - 295k - Bad engine = project car!

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