jbelanger wrote:toalan wrote:I said 2 channels because there is enough analog peripherials to drive 2 of them, more than 2 and you have to start using eternal components which takes away the elegance of using psoc in the first place.
Agreed. That's why I asked about the peripherals.
toalan wrote:All I have is lab grade gas and that is what I use to verify accuracy.
Seems reasonable and I understand that you have limited resources. Have you checked dynamic behaviour or is it only static? And if you've checked dynamic behaviour, how fast can the controller react? Could you see individual cylinder pulses in the exhaust with enough precision to be of use? And have you checked many different units to see how much variance there is between them?
Sorry for the multiple questions but it's easy to compare your WBO2 controller against the others on price. It another thing to compare on features and claimed performance and still even more complicated to compare on actual data (without having to perform the actual tests myself) since your volume is not the same as the big names so there's less user feedback on the net. Is there any objective and independent data available on the net which would include your controller? And I'm aware that objectiveness can be subjective...
Jean
I only have a static rig for testing, I am building a dynamic rig.
In theory based on the sample rate and PID algorithms, the response time is ~10 ms.
I use a ghetto method to compare my response times with others:
-I hook the Feedback signal, black wire of the LSU 4.2, to channel a of my digital scope
-I hook the linear voltage output of the controller to channel b and use that as a trigger for a 500ms capture. I capture when the linear output voltage is greater than ~0.5v, for a 10-20 afr linear output that would mean the trigger is @ 11 AFR.
-With a lighter I give the sensor some rich gas
-I wait until the unit start reading slightly above 10 and then with all my might i blow on the sensor to give it lean gas. The reason I wait until the unit reads more than 10 is because the lowest lambda the bosch sensor is rated for is ~0.68 (10 AFR). So below 10 AFR depending on the controller the behavior is different and it is up to the controller's designer to decide what to do; make the unit freak out, operate the controller at some extreme, etc...
- on the scope will be the captured waveform of the Feeback signal, my scope will capture ~100ms pre trigger and the rest is post trigger.
- You should see a slight blip on the pre trigger portion of the feedback signal, that blip is roughly the instance the lean air hits the sensor.
- Most wideband controllers run a closed loop PID controller to make sure the feedback signal is ~0.45v above virtual ground, (yellow wire on the sensor). You can get an idea of the response time by looking at the fluctation on the feeback signal. The shorter and smaller the fluctuation the faster the response time.
I have done this with my PSOC1 controllers, PLX, and the TE DIY. You can not do this with the innovate units because they do not close loop control the sensor, so looking at the feedback signal will yield no information.
Looking at the feedback signal will only tell you the response time of the controller in properly controlling the sensor. It does not tell you the total response time of from senor to linear voltage output.
The answers to you other questions are too subjective. The PSOC1 design is very rigorous in maintaining accuracy, that is I rely on the internal switch capacitor blocks and the internal voltage reference rather than external analog circuits and 1% resistors. Furthermore each unit is calibrated to remove linear and voltage offsets on the internal ADC, instrumentation amplifier and linear voltage output. There is one external component that is vital, the pump current measuring resistor, for that I use a 0.1% tolerance resistor.
In terms of response time, the sampling rate of my system is much higher than most competing units, I sample the pump current and feedback @ ~1k sps. This allows data to quickly feed data to the PID control algorithms for fast response. It also allows me to oversample and improve lambda resolution.
