Hello all, this is my first post here!
I cracked open an old Oyster Satellite Tracker, something like a much older version of the Oyster 65/85. Inside I found a two heavily down-geared motors each with 4 wires coming out. I can't seem to find any information about these motors, have even tried contacting ITT with no luck.
We touched the thick black and blue wires to a 12V car battery and the motor seems to rotate smoothly and uniformly in a single direction. Connecting the wires the other way turns the motor in the opposite direction. Connected directly to the battery the motor seems to draw about 0.8A.
There are two thinner red and white wires which I assume give some sort of feedback on the rotation of the motor. I have no idea how. Measuring the resistance across the white and red wires with a multimeter just shows a disconnect. Measuring the voltage with the motor connected to the battery shows 0V.
The Motor:
I made a potential divider with a 100 ohm resistor and measured the voltage across the white and red wires.
- If the red wire is connected to positive and the white wire grounded we see nothing, just a constant potential when the motor is connected to the battery.
- If the red wire is grounded and the white wire is connected to positive we see a (slight) oscillation in the potential as the motor spins. It appears like a step function - on/off/on/off. The motor can land on either high or low resistance when disconnected from the battery.
Diagram:
Photograph:
Code:
void setup() {
Serial.begin(9600);
}
void loop() {
// read the input on analog pin 0:
int sensorValue = analogRead(A0);
Serial.println(sensorValue);
// delay in between reads for stability (not accurate due to println in loop)
delayMicroseconds(5);
}
Output:
958
958
958
957
958
957
.
.
.
958
736
958
736
736
958
737
958
736
958
737
736
958
737
958
737
958
737
737
958
737
.
.
.
957
957
957
957
958
In Arduino language 1024 means it is reading 5V across the potential divider and 0 means it is reading 0V. Above I show a few 958,957 which is with the motor disconnected from the battery. This is followed by oscillation between 958 and 737 which happens when the motor is conneted directly to a car battery. Finally I show 957 with the motor disconnected from the car battery. Sometimes (if you time it right) this can land on 737 and it will stay like that until connected to the battery again.
What is going on in the motor? Some sort of diode? A hall effect sensor? How do I get a more stable feedback on the rotation of the motor?
I have tried 200 ohm, 1000 ohm, 10000 ohm resistors in the potential divider, they are all worse and whatever is in the motor doesn't appear to be an Ohmic resistor. Is 5V the right voltage to apply? I have tried 3.3V and it is worse, higher than 5V could blow the Arduino.
Am I even approaching this the right way?
Ideally I would like to have the values ocillate about a digital HIGH/LOW in a very pronounced way so I can use an interrupt to count them.
Please help :D!
For the interested:
I'm using these motors in an attempt to build a homebrew solar tracker, for mounting on an RV. Details of how the project is going are available here, more information on the motors is available here and here