data logger - need to connect 10 V output to 5 V input.

[b4black]

I would like to record knock on a generic data logger. The input channels are all 0-5 volts. The output of the ESC module is 10 volts. Is there a simple way to drop the voltage in half or more to bring it on scale?

Thanks

 

[TurboBob]

what is the input impedance of the logger? The output impedance of the knock monitor?

basically you need a voltage divider

likely 1K resistors will be fine for both.

Bob

 

[TurboBob]

the ground needs to be a "good" ground, a body/dashboard ground will inject its own noise.

B

 

[MCH86GN]

View attachment 287891



what is the input impedance of the logger? The output impedance of the knock monitor?

basically you need a voltage divider

likely 1K resistors will be fine for both.

Bob

No cap to filter out noise? When you say body, do you mean chassis?

 

[TurboBob]

No cap to filter out noise? When you say body, do you mean chassis?

a "good" system will not have noise....

body, chassis , etc. whatever you want to call it is not the right place to ground instrumentation. The engine is the reference ground for all engine control and logging systems.

Bob

 

[TurboBob]

and, back the truck up a minute.

if you are referring to the stock GN ESC module, its output is not analog, but a pulse. I have not logged one myself, I'd be interested to see the data.

B

 

[MCH86GN]

and, back the truck up a minute.

if you are referring to the stock GN ESC module, its output is not analog, but a pulse. I have not logged one myself, I'd be interested to see the data.

B

I have a breakout harness I bought from Caspers, when I get my car back maybe I can connect the breakout and monitor it via a NI analog DAQ, using CANape for it graphing. I'm sure the NI device will be able to sample fast enough.

 

[TurboBob]

i'm sure it will work, the pulse is pretty slow.

Bob

 

[salvageV6]

An optocoupler could work.

I'm not sure how much current is available out of the ESC you need about 10ma to work the LED in that device.

You do have to count all those knock pulses over time so logging them should also include some analysis.

Most knock detectors use counters first then a display of the results over a certain time period.

Graphing them probably won't show you all that much unless you zero in on the events themselves which could only be a few seconds of all the data that you are logging.

I believe the wave shape is normally at 10V and the ESC grounds that signal to make the pulse when knock events occur.

 

[b4black]

I tried the voltage divider already. Seemed to be working until I stepped on the brake pedal and it went haywire. The ground was through the chassis (fender), so I will look into moving it to the engine block.

 

[mikestertwo]

If the resistor divider doesn't work try a resistor and a 5v zener diode.

 

[TTipe]

Noble efforts moving forward but the OE GM esc module does a poor job of separating noise from knock. I have seen some data to support this. Any solution that I have seen to this point requires at least 1 knock to cause the esc strategy to pull out spark. 1 knock count is better than 2, but any knock count takes it's toll on an engine.