This is my first item i am submitting in instructables.This is an Awesome thing found by me.But I feel sorry that I didn't put the image.Leave it,See the step by step instructions and you will be amazed!Do not put this article in any other websites I beg you don't do this without my permission PLEASE!.
Now,to the materials
Voltmeter (one which has a needle(analog))
A motor (from a toy car).
some wires(It should be big enough for your bicycle)
The one am showing is connected to a multimeter!

Step 1:

First,you need to connect the wires to the motor.Now test the motor if it is working--Connect an LED to the motor and rotate the shaft.You should rotate in both directions because the LED wouldn't glow if current is passing throush the -ve terminal of an LED.after testing,you should remove the LEDs


<p>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&gt;VBatt via Voltage controlled switching otherwise, the battery will turn the DC Motor instead.</p><p>Hope it helps..^^,)</p>
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...
You didn't use voltage to figure that out,only distance &amp; time, that's my point. What does the meter do for you??
mark that speed there. I am saying that. You should calibrate the meter using the track, not calibrate the track using the meter.
I told clearly in this instructable that remove the dial of the voltmeter and place the calibrated dial
The only thing clear I saw was your lack of command of the English language.
How does the instantaneous voltage reading on the meter from a random motor relate to speed ??? Don't get it...
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. <br><br>However, speed is Distance over time. Instantaneous speed involves taking the Derivative of the Position Function or The Integral of the Acceleration function.
you can connect the -ve terminal of the voltmeter to the +ve terminal of a rechargeable battery and connect the -ve terminal of the battery to the +ve terminal of the battery. so,while riding,you can generate electricity.
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.

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