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i do not know how to test the current with a multimeter (it would be great if you could explain how to do that).
my arduino motor shield supplies a max of 1.2 amperes to a single motor. will my robot move with 1.2 amperes of current? i know you cannot provide excessive current to the motor, but is it ok to provide an amount that is less than what is required?
Well, You set multimeter to A setting and connect probes so that multimeter is in series with motor. When motor is on and spinning freely, You measure No Load current, when motor is on and You stall it (stop it by Your fingers so it does not spin), You measure Stall current.
You can limit/regulate motor current and that would not affect motor in any negative way appart from loss of RPM and torque.
thanks! but, what is no load current compared to stall current?
how do i use these measurements to determine how much current my arduino motor shield needs to have?
how do i limit/regulate motor current? what component does this?
Current is limited by a resistor in series with a motor.
Current is regulated by IC such as LM317 or circuit such as BJT Current Mirror[/li][/list]More advanced current limiting/regulation can be achieved by microcontroller driven PWM with current sense feedback.
would there be any problem with this, since the motor already draws more current than the board supplies.
http://www.sparkfun.com/tutorial/Ardumoto%20shield/reshoot06.jpgin this picture where would i place the resistor (the motor is being powered by the blue terminals)?
Left/Right MotorNo Load- ~300mAStall- ~600mA (since this motor turns the car both ways, i just measured the no load current for each direction then added them.)
how do i determine the amount of ohms my resistors need to be?i don't know exactly how to use ohms law to determine the resistance, but i know it involves using the voltage and current to find the resistance.
what values would i use in ohm's law: no load or stall?
i will be supplying the motor shield so it should look like this...R = 9v/1.85A (if i was to use stall current)...right?
the steering is rack and pinion and i did turn the wheels to the maximum steering angle.should i physically hold the wheel and resist it from turning to measure stall current?
Neither. You use value that You want Your motor current draw would be limited to.
I'm not sure I get it. If by that You mean that You are going to add resistor between power supply and arduino shield, then NO, You should not do that. You should add resistor between shield and motor (just add resistor to one of motor terminals.
If rack and pinion stop motor spinning, then yes, You were measuring stall current.
Can you clarify that a little or provide an example?
the motor does not stop spinning with the rack and pinion, but the wheels don't turn any further.
Quote from: rahulpwns on November 15, 2011, 09:18:21 PMthe motor does not stop spinning with the rack and pinion, but the wheels don't turn any further.How is that possible? If wheel reach their turning limit, hence rack cannot move any further, so pinion cannot spin any further as well stalling the motor. How come that wheels turn no more and motor keeps spinning?
Also, where could i find a 6 ohm resistor? or a pack of resistors from 1 - 20 ohms? i have been looking and i simply cannot find one.
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