casainho said:
I just calibrate my torque sensor and found it can now measure up to 40 kgs, which is 4x more than before and this means I will get 4x more motor power assistance when I stop and after I need a quick and strong response from the motor, like when I am doing mountain biking!!
I am sure we all want a good torque sensor, that is why most of us prefer TSDZ2 over a Bafang. It is a really fun game, to apply more force with our legs and feel a strong answer from the motor!!
I wrote a wiki page with the process I used to calibrate my sensor (note that I did this process twice, on 2 different torque sensors):
How to calibrate the torque sensor --> https://github.com/OpenSource-EBike-firmware/TSDZ2_wiki/wiki/How-to-calibrate-the-torque-sensor
Just looked at the code to check the ADC conversion:
Code:
// ADC torque sensor
#define PEDAL_TORQUE_PER_8_BIT_ADC_STEP_X100 52 // see note below
/*---------------------------------------------------------
NOTE: regarding the torque sensor output values
Torque (force) value found experimentaly.
Measured with a cheap digital hook scale, we found that
each torque sensor unit is equal to 0.52 Nm. Using the
scale it was found that 0.33 kg was measured as 1 torque
sensor unit.
Force (Nm) = 1 Kg * 9.18 * 0.17 (0.17 = arm cranks size)
---------------------------------------------------------*/
So the value of 52 is too low due to: Force (Nm) = 1 Kg * 9.18 * 0.17 (0.17 = arm cranks size)
It should be: Force (Nm) = 1 Kg *
9.81 * 0.17 (0.17 = arm cranks size)
And therefore the conversion should be 54, up from 52.
Also noticed it says 0.33 kg per ADC step. Assuming that is 10 bit ADC steps it would mean that the 8 bit ADC steps represent 0.33 * 4 = 1.32 kg. Looking at your new data I see that when applying 40 kg on the pedals you get a delta of 25 ADC steps. This is a conversion of at
least 62, up from 54.
Another problem is that the conversion is based on 10 bit values. So for the previous value of 52 it was calculated with:
(1) Force (Nm) = 0.33 * 9.18 * 0.17 ≈ 0.52 ->
52
But should have been calculated:
(2) Force (Nm) = 0.33 * 9.81 * 0.17 ≈ 0.54 ->
54
And with your new data and testing it should be around :
(3) Force (Nm) = 0.4 * 9.81 * 0.17 ≈ 0.67 ->
67
But this only holds true for 10 bit values. The 8 bit values are:
(1) Force (Nm) = 1.32 * 9.18 * 0.17 ≈ 2.05 ->
205
(2) Force (Nm) = 1.32 * 9.81 * 0.17 ≈ 2.20 ->
220
(3) Force (Nm) = 1.6 * 9.81 * 0.17 ≈ 2.67 ->
267
Using the new conversion factor would result in around 5 times higher human power readings. When I was giving
full power with the new development firmware I only got around 100 - 150 watts human power, even less than that. With the new conversion factor I would get closer to 500 - 750 watts. Which is more plausible in a high power situation.
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I think I speak for the whole community when I say that what you have done is very valuable and we all are very grateful. Thanks for the data, time and the money invested in instruments! Together with data provided by Casainho and his great tutorial for adjusting the torque sensor we now know what the appropriate next steps are. Also, a big thanks to every other user that has helped to give the community a better understanding!
