I have been trying to get my improvised tachometer to work and count my cycles properly. i've been working on a DIY pickup winder and i've made my own cycle counter with a small coil and a disk with a magnet on the axis.
i'm quite new to this but i'll give as much information as i can.
the coil generates pulses up to 250mV and the axis can spin up to 8000 RPM.
i have written some code that can kind of count the cycles but i ran into some issues i can't find answers to on the forum or elsewhere
my "sensor" is connected parallel with a 10k resistor between A0 and the ground to make sure i don't shoot unlimited current into the analog inputs.
my 'if' structure seems to run multiple times in less than a millisecond even though i used a delay of 5ms in the loop. this causes the count to be off.
when I use the serial monitor to view the winding counter I can see that the timestamp on 2 different winding numbers is sometimes the same and i can't figure out why.
is this solely a problem in the coding? or is it my entire setup?
You cannot totally trust the timestamp because at 9600 bps the serial interface takes about 1ms to print a single character. With an int you would be printing up to 5 characters which takes about 5ms.
I have used a hall effect sensor for RPM on numerous occasions but I don't know what the maximum RPM is.
I feel like an analog-to-digital converter is not suitable for this purpose (too slow) and that you should consider running the output of the coil through a shaper circuit to create a digital pulse train that you can then feed to an input capture pin of a timer.
The circuit might include a rectifier diode to clamp negative-going transitions from the coil, a comparator and perhaps a Schmitt trigger buffer to clean up the waveform.
thank you both for the input,
i dont know alot about the timing of the programming and converting so this was really helpful.
if i switch to a digital pin and use an external comparator circuit to boost the incoming signal to either a logic HIGH or LOW so i can use booleans, can the arduino process it faster?
also i thought the 9600 was just the baudrate, not the bitrate or am i getting my things confused
