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Help with a simple circuit Answered


I have hassled with this since last year. I have googled over 9000 times, yet I still remain confused, and unable to find a solution myself. I guess it's prime time to seek help from others.

What I have:
Lazer; 4,5 V, 150 mA
2x motor; 1,5 V, 250-300 mA
1x motor; 1V, 50 mA (vibrator motor from nokia phones, and it might work with less)

The idea:
I made a.. Thing.. that had 3 small motors ( the phone ones) that had mirrors on them and the lazer pointed at them, which eventually reached the wall and made made pretty stuff on it..
But that was a prototype, held together with tape, and now I have decided to make a better one.
The V2 of it is held together with screws, has better mirrors (v1 had small fragments of an old hard drive disc), better motors, and looks nicer. If possible then I would like to be able to control the speed of the 2 bigger motors( to be able to create different images)

The problem:
I somehow managed to make the V1 without any resistors without burning anything out, so it only had switches and wires. That doesn't seem to be possible with the V2 that I have planned. I have read almost everything on the internet about it, but I can't make much sense of it, so I figured if someone was to show me how it's supposed be, I would understand a little more. Maybe even finish the project.

What I want:
You may try explaining what I need to do, but all the laws are sooo confusing. I will appreciate any and all posts, be they not on flames. But what I guess would help me the most, is if someone managed to show me exactly what components I need, and where to place them.



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10 years ago

You can adjust the speed with a series resistor or rheostat of appropriate value (probably in the range of 1 to 100 ohms) and sufficient power rating. That is the simplest method. http://en.wikipedia.org/wiki/Brushed_DC_electric_motor#Speed_control

Is the motor current that you listed the stall current or the no load current or just an arbitrary operating point?

If it's an operating point, then the resistance of the first motor at this operating point is 1.5v / 0.25 A = 6 ohms (Note, this number is only constant at this operating point). To make a very crude approximation, if you put 6 ohms in series with this, then the motor speed will be roughly half what it was without the resistor. The resistor may need to be rated for 2 watts or more.