Knock sensor and progressive Leds

[varnish]

I am detecting detonation in a SI engine using a knock sensor (pizeo element).
What I would really like is to have 3 leds that light up as the knock gets more severe.

I have the knock sensor running into an op amp powered by a 9v battery. I am listening to the output with a pair of head phones, but I would like to add a visual output.

The knock sensor is a pizeo element, so as I understand it the more aggressive the engine is knocking the greater the output voltage will be from the sensor.

I was hoping to do something like this;
First led to light when the output from the op amp is between 1-3 volts, the second to come on at 3-6 volts and the third to light up between 6-9 volts.
(arbitrary values I'm not sure what the actual output voltages are, but you get the idea).

The idea is that when no knock is present no lights are on, and under heavy knock all three lights are on.

Any input would be greatly received.

 

[Averagesupernova]

Probably a simple peak detector or peak to peak detector with a sample and hold on the output. This would drive a comparator to light the LEDs.

 

[jim hardy]

try a search on "vu meter circuit" ?

no need to stop at three lights...

http://www.eleccircuit.com/lets-to-build-many-vu-meter-circuits-with-lm3914/

 

[dlgoff]

try a search on "vu meter circuit" ?

no need to stop at three lights...

http://www.eleccircuit.com/lets-to-build-many-vu-meter-circuits-with-lm3914/

That sounds like a perfect solution. Here's one using the LM3916.

http://www.canakit.com/media/catalog/product/cache/2/image/300x/5e06319eda06f020e43594a9c230972d/R/1/R134FRONT-FINAL.gif

And they have more kits along this line.

LED Blinkers & VU-Meters

 

[alphy]

I would suggest using a microcontroller to process the output from the knock sensor and control the LEDs accordingly. This would allow for more precise and customizable thresholds for each LED, as well as the ability to adjust the thresholds as needed. Additionally, the microcontroller could also be programmed to log and record the knock data, providing more detailed information for analysis. Using a microcontroller would also eliminate the need for a separate op amp and could potentially reduce the power consumption of the system. Overall, this approach would provide a more efficient and accurate way to monitor and visualize engine knock.