Azurit 10a

[kalla]

Hello all,
In the mower.cpp is in line 83 the motorMowSenceScale= ADC2Voltage(1)*1905 discribed. Where is the value 1905 coming from?
The reason for my question is: I have a motor-driver BTS7960 to drive my 350W motor and a current-sensor ACS712 (20 A), for the max current of my motor is nearly 17 A.
I don´t know what to write in the code.
Can anybody help me?

 

[thorsten-ac]

Hello,

I think this is just a multiplier that was given by the current sensor, but I can't tell you exactly.

 

[kalla]

Hallo thorsten-ac,
vielen Dank für die schnelle Antwort. Der Stromsensor ist im MC33926 und da kann ich diesen Wert für die Empfindlichkeit leider nicht finden.

 

[Fürst Ruprecht]

https://www.pololu.com/file/0J233/MC33926.pdf

Auszug aus dem Datenblatt:

„FEEDBACK (FB)
The 33926 has a feedback output (FB) for “real time” monitoring of H-Bridge high-side output currents to facilitate closed-loop operation for motor speed and torque control.
The FB pin provides current sensing feedback of the H-Bridge high-side drivers. When running in the forward or reverse direction, a ground-referenced 0.24% of load current is output to this pin. Through the use of an external resistor to ground, the proportional feedback current can be converted to a proportional voltage equivalent and the controlling microcontroller can “read” the current proportional voltage with its analog-to-digital converter (ADC). This is intended to provide the user with only first-order motor current feedback for motor torque control. The resistance range for the linear operation of the FB pin is 100 <RFB <300 .
If PWM-ing is implemented using the disable pin inputs (either D1 or D2), a small filter capacitor (~1.0 μF) may be required in parallel with the RFB resistor to ground for spike suppression.“

Gruß Fürst Ruprecht

 

[gk]

about 1905:
adc2voltage returns the reading of the sensor in volts.
the current is calculated in mA.
The current sensor of the mc motordriver has 525mV/A.
1000mA/0.525V= 1904,76
for Acs712-20 it should be 1000mA/0.1V=10000
That is if the adc is calibrated, else subtract ca 2,5V from adc2voltage.

 

[kalla]

Thanks "Fürst Ruprecht", but I have read the Datenblatt and seeked the value 1905 which I did not found.
Thanks "gk". That was the explanation I wanted to hear and for to understand.