.:madworm:.'s photos with the keyword: knock sensor

A single supply non-inverting amp with pulse stretcher. It's also got an offset 'knob'. The LM2940 is a dual amp, so maybe I'll add some more pulse shaping. It sucks that all the easy stuff requires symmetric supply voltages. But using just 5V also means that there won't be any over-voltage or negative voltages that could kill the AVR. The blue curve will be integrated by a microcontroller.

A single supply non-inverting amp with pulse stretcher. It's also got an offset 'knob'. The LM2940 is a dual amp, so maybe I'll add some more pulse shaping. It sucks that all the easy stuff requires symmetric supply voltages. But using just 5V also means that there won't be any over-voltage or negative voltages that could kill the AVR. The blue curve will be integrated by a microcontroller.

LM2940 non-inverting amp, no pulse stretcher yet. All this amplifier business is a black art of its own. In retrospect I must find that all the lectures I've taken at uni regarding electronics were only capable of teaching the very basics, if at all. I didn't study EE though, but some other natural science which is highly unpopular among most people, especially at school. And I still don't know sh*t about you name it. So much to know, so much already forgotten.

A single supply non-inverting amp with pulse stretcher. It's also got an offset 'knob'. The LM2940 is a dual amp, so maybe I'll add some more pulse shaping. It sucks that all the easy stuff requires symmetric supply voltages. But using just 5V also means that there won't be any over-voltage or negative voltages that could kill the AVR. The blue curve will be integrated by a microcontroller.

LM2940 non-inverting amp, no pulse stretcher yet. All this amplifier business is a black art of its own. In retrospect I must find that all the lectures I've taken at uni regarding electronics were only capable of teaching the very basics, if at all. I didn't study EE though, but some other natural science which is highly unpopular among most people, especially at school. And I still don't know sh*t about you name it. So much to know, so much already forgotten.

As the 8pin LM2940 op-amp is a dual amp, I've distributed the amplification to both amps. The first stage still adds an offset and has adjustable amplification, the 2nd stage is a fixed at a factor of 11. I've also added a low-pass filter at the output to smooth the signal some more. C5 was added for AC coupling and must be at least as big as C1. D2 was added to allow C5 to be discharged and be ready for the next pulse.

I'm still using my old scope ;-)

x: 10ms/div y1: 200mV/div y2: 1V/div Taken from here and using a 10x probe. y1: sensor voltage (minus offset) y2: amplified and stretched