Syscrush said:
Gotcha. I misunderstood - I thought that there was feedback between the measured amount and the current sent to the heater, not just signal conditioning on the measured amount. Thanks.
More importantly, I'm glad to hear you're feeling good about how it's working as you continue to spiff it up.
I am anything but an expert on this, h_ll, I very honestly have no idea what the bosch data sheet (bosch writes the worst sheets I've ever seen) is trying to tell me in most cases. The HW is built so I should just be looking at the application section...but there isn;t one so not being an electronic person who "sees" that the chip block diagram does, I'm left kind of guessing.
So, this is all "as I understand it" There are 2 main outputs from the chip then ECU also shows me some other info it gets over the SPI buss including a UR_cal signal. My understanding is I heat the sensor until the UR signal matches the UR_cal signal and that means the cell resistance is correct and the output signal UA mis accurate. Sounds simple but the UR signal seems to like to pin itself against the upper limit so heat, heat, heat,...nothing...BAM its on the lower limit. PID controllers just don't work well on things like this.
Then add to it that the best I can tell 2 or the 3 sensors I have are bad and by chance the only good one was plugged into the innovate controller so I'm loking at it's output and wondering how the heck I get that...the answer turned out I don't because the sensor I'm using is broken. The brand new one, which is actually years old must have gotten dropped as its got an intermittent short...occasionally it works but....the other old one from the #8 cyl bank just outputs the wrong thing, it should be about a 0.5-2.5V signal and ita more like 1.2-3.6 but can be driven to the right range if I move the UR control point to about 3.3....which had me thinking I must have read the bosch sheet wrong and missed the magic offset.....nope, just a bad sensor, put the last one on and magically 2.5V cal point is correct.
This has had me tearing my hair out honestly and I've completely given up on smooth, continuous, elegant solutions. Right now the heater just comes on for 5 seconds, but on a limiter function as you suggested so on above x and off and below/y just to put some heat in it as it acts very different cold than warm. Then it goes to PID, but if it gets above 4.8V the limiter kicks back on and drives down off the upper limit what the PID can see it moving. Then I have 2d PID table that look at both UR volts and the slope to decide how aggressive to act. This is for sure a brute force approach.....I just got it going like this last last not but it seemed to be working better than previous attempts but needs a bit more tuning.
Contrast this with a guy making his own controller from scratch over the the rusEFI forum who said on his a simple PID is all that was needed.....that is what I was expecting then all these issues, including the ECU company owner saying "why not just buy an external controller and use your time on more important things?" had me believing all the issues I'm seeing are normal and why most just use an external dedicated controller......then rusEFI guy says its simple and plans to sell the units that cost about $8-$10 to make but I don't know the final price point.....that just doesn't match what I'm seeing.
Rant over...the battle continues.....hoping the blcok comes back soon so I do have better things to do and can justify setting this aside.....