buba wrote: ↑
Jul 06 2019 8:38pm
casainho wrote: ↑
Jul 06 2019 8:22pm
I took the risk to disassembly the torque sensor... and I moved the hall sensor to very near of the magnets. In the end, the torque sensor is working and the rest ADC value is now 17 instead of the previous 62!! The max value is almost the same as previous: 82.
Well, it is not working well as I need to make 25 kgs for the torque before the torque sensor starts increasing over 17... seems that in a few hours will need to make extra work to ride my bicycle on the planned trip
So, maybe the hall sensor is saturated because is to near the magnets...
So it improved the rest value but there is an offset of 25 kg? Wow! I need to study the entire torque sensor package and understand how it works. Because right now it seems as human power readings will be impossible for all users to have... Did not expect this.
Hi Buba, I think that Casainho is right, the two bolt are the key, but for adjust the position of hall sensor we have to do a micrometrical movement on sensor. I try to explain me better: before adjust the hall position I was in this situation:
Rest ADC value: 52, Maximun ADC value: 96, so a resolution of 44 ADC steps
After 3 attempts, moving in small steps further and further away from the magnet the new readings are:
Rest ADC value: 35, Maximun ADC value: 96, so a resolution of 61 ADC steps
I think I can still distance the sensor from the magnet until I have a resolution of 70-75 ADC steps, but there is a lot of time for disassemble and reassemble the torque sensor and a resolution of 60 ADC steps could be enough!
Also seems that at the right position of hall sensor (at near 60 ADC steps resolution) we have a linear output to the force applied, but for this I wait the digital dynamometer that I ordered whit a 90kg of capacity and 0,1kg resolution for a detailed report!
Now after a fine calibrating, there is a problem on the pedal sensor torque reading (menu 9 - 3): the parameter reach the maximum value of 255 when the ADC pedal torque sensor reach value of 68, so in this case I can use about half of the sensor capacity...
I think the maximum ADC reading is variable for each torque sensor, but still fixed for each unit, due to the small differences in the windings of the two (transformers) or the magnet near the hall sensor, from unit to unit.
For calibration the torque sensor the rest value is read every time the unit is powered on, right?
So for improve sensor torque experience and resolution it would take a user modifiable parameter regarding the maximum ADC value (the parameter can be easily read from menu 9 - 2 from each user by applying the maximum pressure on the pedals)
Another usefull parameter for fine calibrating the user human power could be an editable parameter that adjust the kg applied for each ADC step (assuming the linear output of sensor)
Thanks guys, your work on this firmware is exceptional!