I need to found the value of ke (Back EMF constant(Vs/rad)) , km (Motor Torque constant(Nm/A)) and R (Terminal Resistance(Ohm)) of this motor, does some one know this value??
I just now took a measurement of one of the wheels I have....
Using a 3.7V Li-Polymer Battery rated at 15C 2000mAh, the motor has a torque of 2 ft/lbs (2.7Nm) at 3.7V
Using an automotive battery measuring 12.8V, the motor has a torque of 9.5 ft/lbs (12.9Nm) at 12.8V
The motor coil resistance (resting) is 1.7 Ohms
I'm not sure how to measure the Back EMF constant(Vs/rad) but I could measure the inductance (resting) of the motor if that would help.
According to this site and based on my torque calculations, the Ke agrees with the formula and calculates to about 0.08
The inductance of the motor measures about 90.4uH based on using the method described below. I used two known %1 inductors with a value of 47uH and 100uH
Method to determine an unknown inductor based on results from a known inductor:
1) Determine the resonate frequency of your known LC values.
2) Substitute the known inductor with the unknown inductor, and measure the frequency.
3) The unknown inductance value can be determined by the following equation:
F1 = measured frequency from step 1
uH = known inductor value
F2 = measured frequency from step 2
uH! = unknown inductor value
uH! = uH * F1^2 / F2^2
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IC Layout Engineer
Parallax, Inc.
So, i need to convrt the applied voltage to PWM signal in spin code, does someone know how to do this? The PWM signal as the input to HB-25 (#29144), and i use CJ_HB25.spin at obex.parallax. At thad code i need to identified pulse1 as input PWM pulse to Motor1 and pulse2 as input PWM pulse to Motor2. I need some direction... thanks b4
Hi ,
This is an old post but it seems that the calculated torque is not complete
becuase you haven't considered that friction and efficiency.
Sometimes the efficiency of a motor with reduction could be 60% or less.
What about the torque if you think about efficiency ?
Comments
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
I just now took a measurement of one of the wheels I have....
Using a 3.7V Li-Polymer Battery rated at 15C 2000mAh, the motor has a torque of 2 ft/lbs (2.7Nm) at 3.7V
Using an automotive battery measuring 12.8V, the motor has a torque of 9.5 ft/lbs (12.9Nm) at 12.8V
The motor coil resistance (resting) is 1.7 Ohms
I'm not sure how to measure the Back EMF constant(Vs/rad) but I could measure the inductance (resting) of the motor if that would help.
According to this site and based on my torque calculations, the Ke agrees with the formula and calculates to about 0.08
www.gizmology.net/motors.htm
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/22/2009 7:50:20 AM GMT
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·"If you build it, they will come."
The inductance of the motor measures about 90.4uH based on using the method described below. I used two known %1 inductors with a value of 47uH and 100uH
Method to determine an unknown inductor based on results from a known inductor:
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
torque approx 2.0 ft/lbs ( 2.7Nm) at 3.7V
torque approx 9.5 ft/lbs (12.9Nm) at 12.8V
torque approx 11.1 ft/lbs (15.0Nm) at 14.5V
Motor coil resistance is approx 1.7 Ohms
Ke approx 0.08 Vs/rad
inductance approx 90uH
Reference:
www.gizmology.net/motors.htm
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/22/2009 6:25:14 PM GMT
This is an old post but it seems that the calculated torque is not complete
becuase you haven't considered that friction and efficiency.
Sometimes the efficiency of a motor with reduction could be 60% or less.
What about the torque if you think about efficiency ?
Mark
The Eddie specs, on page 16, will give you an idea of what load the Motor Mount and Wheel Kit can support: