Need expert opinion on my circuit design (to filter 12V power)

MisterBill2

Joined Jan 23, 2018
6,973
My guess is that the problem has nothing to do with the power supply, but that the processor is not fast enough to handle the pulses as the engine runs faster. This is simple to verify by temporarily powering the circuit from a battery instead of the electrical system. Observe the reading at idle, and then increase the engine speed . My experienced guess is that the problem will remain.
The solution is to not use a computer for a tachometer application, but rather use a tachometer IC, such as the LM2917. Still available after many years because it works so very well. AND it includes an internal voltage regulator circuit.
 

Thread Starter

JunkieNL

Joined Mar 19, 2020
29
My guess is that the problem has nothing to do with the power supply, but that the processor is not fast enough to handle the pulses as the engine runs faster. This is simple to verify by temporarily powering the circuit from a battery instead of the electrical system. Observe the reading at idle, and then increase the engine speed . My experienced guess is that the problem will remain.
The solution is to not use a computer for a tachometer application, but rather use a tachometer IC, such as the LM2917. Still available after many years because it works so very well. AND it includes an internal voltage regulator circuit.
The Arduino processor isn't handling any pulses. It just ask the motorcycle's ECU for the rpm a few times per second. The Arduino can show the rpm and be idling 99.9% of the time.

working example on youtube
 

MisterBill2

Joined Jan 23, 2018
6,973
The Arduino processor isn't handling any pulses. It just ask the motorcycle's ECU for the rpm a few times per second. The Arduino can show the rpm and be idling 99.9% of the time.

working example on youtube
OK, perhaps the engine controller gets too busy to reply. And with the price of an ECU being what they are, I would not touch it. An external tach is much safer in that it does not risk damaging the ECU.
 

Thread Starter

JunkieNL

Joined Mar 19, 2020
29
OK, perhaps the engine controller gets too busy to reply. And with the price of an ECU being what they are, I would not touch it. An external tach is much safer in that it does not risk damaging the ECU.
I am willing to take that risk, since I am not tampering with the ECU. I am just asking it for information in the same way that the OEM tach would. The ECU is working within normal operating conditions.
 

Thread Starter

JunkieNL

Joined Mar 19, 2020
29
I want to thank everyone for replying, it was very helpful to me. Currently I am waiting for some parts I ordered in China, so it will take some time before I will be able to do a field test. In the meantime I will be using my time to add a fancy display and a GPS module. I will post a follow up when I get it working.
 
Last edited:
  • series schottky (low 0,3 V drop out) diode of power input
  • loose inductor, put ferrite chip / Resistor in front of the TVS (increases TVS life time)
  • small capacitance ceramic and large capacitance electrolytic / plastic caps in parellel, I guess this was already covered
  • Tantalums will eventually be self ignite in harsh environment
 
Top