i have 2 motors from a old rc car i took apart but i am confused to whether i can use them one comes with x2 green Resistors solder on the circuit that's the back motor and the over is from the front steering which dose not.i was also wondering if i could desolder the boards from off the motors and just have wire there any help on how to use the motors with out frying my arduino will be grate
the pic is not grate but best my phone can do
basically how to get them running with out braking the arduino
frank10:
i have 2 motors from a old rc car i took apart but i am confused to whether i can use them one comes with x2 green Resistors solder on the circuit that's the back motor and the over is from the front steering which dose not.i was also wondering if i could desolder the boards from off the motors and just have wire there any help on how to use the motors with out frying my arduino will be grate
Notice the board on the "steering" motor - notice how both boards look the same, with the exception of the missing parts? See how where those missing parts are labeled on the board as "L1" and "L2"? Notice the schematic symbol of a rounded bumpy line for each of those on the board?
What I am getting at is these parts are -not- resistors; they are actually "axial lead" inductors - small coils which are designed to pass DC voltages/current, but not AC:
Such inductors come in many shapes and sizes (as you can see in the wikipedia article); the color bands - like a resistor - indicate the value of the inductor. Inductors are typically used in filtering circuits. Axial lead thru-hole inductors typically have a body colored green or blue to differentiate them from similar sized thru-hole resistors.
Also note on both of these boards the capacitors. Capacitor work in the opposite manner of an inductor - they can pass AC, but block DC.
In the case of these motors - the purpose of all of these parts is to filter motor noise; when small (or large) brushed-DC motors run, the commutator inside the motor sparks (some more than others depending on design), which results in a ton of electrical noise, which can travel back up the motor wires to the controlling circuit (h-bridge, etc). This can lead to the circuit failing or otherwise malfunctioning.
In the case of the drive motor - the motor likely is under a heavier load than the steering motor (and because it is running more or less constantly compared to the other motor) - and thus generates more noise. So - those inductors allow the DC current to run the motor, but block the AC signal coming back out of the motor. In addition, on both motor PCBs, the capacitors (the small SMT parts) are likely soldered between the terminals of the motor - shorting the AC signal across - but allowing the DC to pass into the motor (you will also sometimes see capacitors soldered from each terminal to the metal "can" or case of the motor - but that doesn't appear to be the case here).
The reason there are no inductors on the steering motor is likely because since it isn't used as much (nor has as large a load on it), it didn't produce enough noise in testing to be a concern to the designers/engineers of the toy.
That explains the why and what; as to your question of removing them - I would advise that you leave them on; if you can (and depending on your application of the motors), you might want to purchase and incorporate the same sized inductors for the other motor as well. It couldn't hurt - depending on what your project is, of course.
Generally, though, you can get away with a simple small value non-polarized ceramic capacitor across the terminals of a small brushed DC motor to reduce the noise output; if you wanted to know what size you should use (or whether you need to add inductors or whatnot), that would depend on the amount of noise generated by the motor - and to know that, you would need to use an oscilloscope to see the noise being generated by the motor under load. Once you knew the approximate frequency range and voltage levels of this noise, you could then calculate (or perform trial and error fitting) what is needed for the capacitors and/or inductors to act as a filter to remove or reduce the noise in the system.
You want to keep this noise out - especially in a microcontroller system - because such noise can cause everything from blown parts (rare, but it can happen depending on the voltage level of the noise) to erratic operation of the microcontroller (generally, in this case the noise will travel on the ground side of the circuit). In extreme cases where the noise in the operation of the motor is great (beyond what can be controlled by simple filters) - you might need to use isolation of some sort to keep the motor side of the the controller separate from the digital input signal side (opto-isolators or other devices are typically used for this).