Voltage rise delay circuit

[boonie]

I'm new to this board and have a little analog problem that maybe someone can help me with.

I'm trying to find a way to delay the rise in signal voltage from the Charge Air Pressure Sensor on my car. I would like to slow the signal rise down so that when my turbocharger starts to increase manifold pressure, the sensor's output is delayed and doesn't rise so sharply. This is quite important since the engine's ECU is using this signal to compare actual pressure inside the intake plumbing to the requested level that it uses to generate turbo boost. I am using a separate boost controller to control the turbo and therefore boost, which spools the turbo too quickly and generates boost too quickly. This causes an undesired effect called "limp mode", which is when the ECU limits boost to 5psi.

Basically, the Charge Air Pressure Sensor works by converting air pressure into a signal voltage that can read anywhere from 0-5 Volts.

I would only like to reduce the time it takes for the signal to reach the desired level and not the maximum voltage (i.e. boost) that the ECU is seeing.

Is there anything that I can add to the signal wiring, lets say between the signal wire and signal ground that can slow this increase in voltage down?

I was thinking of a capacitor in parallel with a resistor, installed between the signal wire and signal ground. ???

Any suggestions would be greatly appreciated

 

[caesarye]

I think you may use a capacitor.What you want to do is to delay the output signal of the sensor.Add a parallel capacitor in the path between the sensor and the MCU.
Because th e capacior will slow the rise speed of the signal ,perhaps it will do.

 

[boonie]

Thanks for the response. I'm going to try and log the voltage from the sensor on a typical "run" in the car. Once I have that, I'll build a simulator and start testing from there.

Any other suggestions welcome.

Thanks.

 

[echo47]

I would first try to gather a little more information:

1. The voltage waveform(s) you see right now.
2. Your desired voltage waveform(s). Maybe acceleration and deceleration need to be different.
3. The approximate output resistance of the circuit driving the signal.
4. The approximate input resistance of the circuit receiving the signal.

That information would help to design the filter correctly on the first try.

Sounds like a fun project. Varoom!