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## Introduction: .

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### Teacher Notes

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## Step 1:

Now connect this calibrated speedometer to the motor and the item is ready!Now connect the motor to the wheels of a Bicycle.
How is it? Awesome? If it is good thanks.Here's the picture of an analog voltmeter. Participated in the
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## 10 Discussions

Take it easy there guys. He's a 15 yr old kid. I mean he has the abstract nailed down, though not the exact principle. But yes, modern electronic speedos use the same concept. The only difference is the sensing circuit(DC motor) has a fixed coil moving magnet configuration instead of the DC motor configuration(fixed magnet moving coil configuration) to reduce wear and tear from the bushings/contactors. And ADC(analog to digital converters) to convert your analog ACV or DCV signal into digital signals to display it in LCD's or 7 segment displays. A little correction though, for it to charge a battery, you'd need to regulate the signal from the DC Motor and should generate Voltage>VBatt via Voltage controlled switching otherwise, the battery will turn the DC Motor instead.

Hope it helps..^^,)

Yeah, that's cool ! But, that stuff was written when I was about 13 years old... So, I was new to this instructables and internet stuff at that time. I would be editing this instructable to include theory and generalize the subject matter to DC motors and its applications...

A DC motor generates a voltage if you apply a force on the shaft (ie turn it). This induced voltage is proportional to the speed at which the magnetic field is going through a coil of wire (and vice versa) Thus meaning the faster you turn the motor the more voltage it produces and the higher your speed.

However, speed is Distance over time. Instantaneous speed involves taking the Derivative of the Position Function or The Integral of the Acceleration function.

See, the voltage produced by the motor is proportional to its rotational speed.So you can ride a bicycle on a distance-marked track.suppose I am going for a ride.its distance is 100m and I have covered 100m in 8.8sec.now use the formula s=d/t.So,100/8.8=11.36m/s.Now convert it to km/h.1km=1000m so d=11.36/1000 1h=3600sec so 1/3600. now divide.To divide,you should take the reciprocal of the second fraction and multiply.so,11.36/1000*3600/1=40896/1000.now cancel each other.so,40.896km/h.