I am relatively new to electronics, and after going through tutorials I decided to create a RC Car with an Ardiuno. When I finished it, I found that the car's motor would spin extremely fast, but had no torque to push the car.
I've heard that increasing current increases torque, but is that true? And even if it is, how do I increase current in my circuit? (I have only 1 resistor, and I can't think of any way to reduce resistance further).
I have added a drawing of my circuit as well as a schematic (using Fritzing).
EDIT: After a warning by jremington about the Arduino expecting regulated voltage, the Arduino is receiving power from USB (removed the 3.3V wire)
A hand drawn schematic would be better than either of those representations, but why do you make a connection to 3V3? You should never attempt to power a motor using the Arduino, and may end up destroying the Arduino with the present setup.
Google "Arduino dc motor control" for lots of examples.
Actually, the motor seems to gets power from the DC, and the Arduino seems to only get power from the battery when I connect to the the 3.3V/5V pins. I have removed the USB cable and left the Arduino with only the circuit I showed and the Arduino still had power and could still run the motor, making me think that the battery is providing power to both the motor and Arduino.
@florinc:
The interesting thing is, to make the RC car I took apart one I had and just used its motors/fuselage. The RC Car I took apart had no gear box, so I'm stumped on how it managed to have torque . . ..
DC motors, at least the ones you are talking about do not require extra resisters.
They are designed to work at a certain voltage. You only need to apply that voltage to make it work as designed, people control motors by controlling how much voltage goes to the motor via several different methods.
Current is what gives the motors more torque from a generalized point of view, but you cannot change that once the motor has been built.
The motor has a coil with a resistance that is constant. Ohms law says that Voltage = Resistance * Current, so if you increase the voltage to the motor the current will have to increase.
However the coil is only designed to handle a certain amount of current, if you just add more to it you will likely damage the motor.
If you want more torque you cannot do it with the motor you have as is. You need to buy a motor that is designed to give more torque. Naturally at the same voltage it will probably be much slower though.
The arduino regulators are not designed to power motors, even toy ones. You need to know some key information about your motor before you could even think of attempting that.
Resistors are very cheap, 10Cents is considered more or less a ripoff. Online you can get 100's for a few bucks. Shipping is where most of the cost comes from.
jremington: Thanks for telling me! Guess I should just power Arduino by USB until I get a regulator. :
harddrive123:
If you want more torque you cannot do it with the motor you have as is.
The thing is, I am using the motor that came with a RC car (which I only removed the control board for, planning to replace with an Arduino). I still have the fuselage and motors which the RC car had, but I cannot replicate using Arduino the torque that the RC car had before I dismantled it. This is why I want to know how did the car's manufacturers increase the car's torque using the same motor that I am using. All I can tell by seeing the car's former control board is that they added a lot of transistors and one capacitator . . . .
For brushless DC motors, voltage determines speed, current determines torque.
if you want to trade speed for torque, you incorporate a gear-down system (gear box).
Remove any resistance from the motor supply path (not from the base/gate to arduino). What's the on resistance of your driver transistor? Replace it with a low on resistance, high amp, logic level MOSFET.
if that don't work, get a beefier battery (higher discharge rate, not voltage).
I understand that this could ruin my Arduino, and have already decided to only use a USB Cable as a source of power for it until I get a voltage regulator.
The way I started making the RC car is by taking apart an existing one I had that had a lot of torque. It had no gearbox whatsoever. I'm still using the same battery source the car was using and the same motors. However, I'm unable to replicate what the car's manufacturers did using the exact same parts (except for the 'control board' which I planned to replace with an Arduino). This led me to believe that they increased current somehow on their control board using some piece of circuitry I don't know, which is why I asked a question on this forum.
There is no way they had a DC/DC current booster on a toy car :o
I can sort of relate to what your saying. I had an ancient radio shack toy car that was ~20 years old that buzzed around really fast in its day. Used like 8 AA. Once I tried to drive it on a DC voltage I got nothing from it but a slow turn and no torque.
Toy cars have to be simple, they don't want to put a processor in it. So what's the most effective way to drive it from a R/C remote? My bet is to drive the motors directly from the R/C signal which is likely a PPM or servo type.
They probably wound the motor coil so that it could be driven from that type of signal. Once its wound for PWM or PPM it wouldn't work very well on straight DC voltage.
My bet is to drive the motors directly from the R/C signal which is likely a PPM or servo type.
Do you know what you are talking about? Motors take real power, logic signals are milliwatts at best.
We need to know what the motor is rated at, voltage, load current, internal resistance/stall current.
Then you can choose a driver that will be suitable.
If you are using the same motor, same drive train, and same battery,, the motor is brushed DC, not BLDC,,, then the problem would seem to be in the motor supply branch. "What's the on resistance of your driver transistor? Replace it with a low on resistance, high amp, logic level MOSFET."
polymorph:
I am providing power to the motor using the DC battery source (4 AA batteries) that the car already had.
harddrive123:
When you mean 'wound motor coil', due you mean a bronze wire wound around something, because there is a copper wire wound around a little black 'stand' in the RC car's former control board . . .
MarkT:
Unfortunately I can't figure out the motor's part number to find voltage, current, etc.. Those Chinese manufacturers soldered right over half of what was printed on the motor
Upon further research, I found a way to increase voltage called a boost converter. I am starting to think that the RC control board had one because it has all the required parts on it (diode, transistor, capacitor, etc.). Is it feasible for an RC car to have this? The RC Car has two capacitors on it, one at 16V max and another at 50V max. I am starting to think that the RC car's manufacturers boosted the voltage of the car using boost converter circuits, with the 50V capacitor for the drive motor and the 16V for the turn motor.
Try connecting the motor directly to the 4 AA cells. Do you get torque now? I really doubt they boosted voltage in a toy. Much cheaper and simpler to get a motor with the correct windings.
