I'm going to turn it into a self balancing robot. Just because. I have motor drivers and accelerometers, but I was wondering if I could re-use some of the original electronics:
What we see here is the two motors, the driver (bigger green PCB) and the RC unit (smaller green PCB). The driver PCB has a few single transistors (on the other side of the PCB), as if there was no integrated circuit, the transistors doing the H bridge stuff.
And this appears to be the RC unit. A black wire to the left is the antenna. The chip probably doing the on/off based controlling of the two motors, according to the received remote signals. The lines R, L, B and F puzzle me a bit. Could it be as simple as only one of them being 1 at a time?
R: rotate to the right (CW)
L: rotate to the left (CCW)
F: move forward
B: move backward
So instead of replacing everything with new electronics, I'd like to replace only the small PCB with an Arduino. And see what happens, if the signals on R, L, F and B would be PWM signals. And what happens if both L and F are 1 at the same time. Or maybe one should receive a PWM signal and the other the same signal inverted.
Any thoughts, any piece of advice, before I do a bunch of unnecessary errors?
if you want to start such a project a digital multimeter (in short DMM) is a must.
You are almost lost without a DMM.
Without a DMM it would be very hard to do even simple measurings.
Optimal would be to have a 100 MHz two channel digital storage oscilloscope.
But this is in investment of $300
For analysing digital signals (= signals that are either 0,0V or 5,0V (3.3V but nothing inbetween)
a 24 MHz 8 channel logic analyser will do the job. Costs about $15
From the pictures it does not clear if this car has two motors.
Two motors would mean two h-bridges.
Again: By measuring with a DMM you will find out how the control works
Could be an interesting project to learn. Though if you prefer starting quick with the balancing new electronics are easier to use
It has two motors. I'm not quite sure what kind of motors they are. And I guess there are two H bridges. Four wires go to the motors, M1A, M1B, M2A, M2B. Typical for a two motor driver.
And I do have a multimeter, but not an oscilloscope.
I guess I try to re-use the driver, before I replace it. I just have to figure out the voltage of the logic level - as well as the logic itself. If that works, I might not need to concern about the volts and amps for the motors and whether my replacement driver can handle them. I just use the original battery or a similar battery.
This is just a matter of measuring as well.
If you know how to measure current (ampere) you can measure the current under load to see what values there are.
Measuring current is fundamental different from measuring voltage.
If you would try to measure current the way you measure voltage you would create just a shortcut.
This means you really have to know what you are doing.
You can use any battery of the same voltage.
Even a battery that woud be 10 or 50 times bigger.
Well, the original controller may do just on/off logics, and that sure is not enough for a balancing robot. We'll see how it goes, when I replace the smaller PCB with an Arduino (together with a logic level converter, if that is needed) and I output PWM instead of just on/off, using the original driver (the bigger PCB).
Eight heat sinked transistors and some other stuff.
The motor measures some 22 ohm. With 6 V, that's not more than 200 – 300 mA. I haven't powered everything yet. I bet the measures will differ.
The voltage over Vdd and Gnd is 3.7 V, when I connect the charged 6 V battery (which gives 6.9 V without load). So I bet the logic level is more like 3.3 V than 5 V. Then I baldly shortcircuited Vdd and each of the four pins in turn: Left motor rotates cw, Left motor rotates ccw, Right motor rotates cw, Right motor rotates ccw. Simple as that. I haven't picked an arduino yet. But if it's a 3.3 V thing, I'm all good. Just a resistor, say 150 ohm between each pair of pins. If it's a 5 V thing, I'll build a simple voltage divider on each pair of pins. Running just 3.7 V into one pin created a 6 mA current.
Next test will be with an Arduino. And the test will include PWM signals.
So, when R goes high, one motor runs cw. When L goes high, same motor runs ccw. What may happen, when both L and R are high? Motor braking? Shortcutting inside the H bridge circuit?
The labels R, L, B, F are misleading. I bet they refer to RC car models with two driving rear wheels and two steering front wheels. They then used same PCB components for these tank steering cars.
Test done. It worked. At least the motor reacts to various duty cycles of PWM. But the motor has no wheel, so I have no idea about the torque on lower duty cycles. I also don't know much about how to determine whether the motor actually is suitable for PWM. I guess the next test is to reassemble the car with an Arduino and have it actually run.
