Learning About VCR Jog Wheel

Project Log

( 9 June 2009 )

A while back I obtained a jog wheel from (I assume) a VCR. It contains a rotary encoder attached to an inner spinning wheel and an outer wheel which moves probably ~120 degrees left and right with a spring return to centre.

There's a Rotary Encoder page on the playground with a variety of approaches but there is also Quadrature Encoder library.

I've searched on all the identifying numbers I could find and couldn't find any information. The underlying component appears to be manufactured by Alps.

There is an eight (8) pin connector with 7 grey wires and 1 brown wire (pin 1).

Presumed pin allocations: (1) Ground? (2) Encoder A? (3) Encoder B? (4) -- (5) -- (6) -- (7) -- (8) --

Ah, it all becomes clear: Jogging and shuttling with Arduino which suggests the shuttle ring uses grey encoded output.

The connector has 2mm headers rather than 0.1" so I had to wire up an adapter. I can't reliably detect movement from the jog wheel, I'm not sure why.

( 27 June 2009 )

Copying and pasting code is a bad idea. Remember that. :-) Discovered I was never configuring one pin because I configured the other pin twice. :-) Also, changed the order as it seems ground is the middle pin.

Successfully read jog wheel result consistently with correct count.

From the code on the page linked above I add:

int PIN_C = 14;
int PIN_G = 15;
int PIN_D = 16;

void setup() {
  pinMode(PIN_G, OUTPUT);
  digitalWrite(PIN_G, LOW);

  pinMode(PIN_C, INPUT);
  digitalWrite(PIN_C, HIGH);

  pinMode(PIN_D, INPUT);
  digitalWrite(PIN_D, HIGH);

  Serial.begin(9600);
}

And change the digital read to (I know, overcomplicated):

  a = digitalRead(PIN_C);
  b = digitalRead(PIN_D);

  // inverted
  if (a == LOW) {
    a = HIGH; 
  } else {
    a = LOW;
  }

  if (b == LOW) {
    b = HIGH; 
  } else {
    b = LOW;
  }

The inversion above is because I use the internal pull-up resistors whereas the code expects a external pulldown. I haven't checked if this inversion is actually required for correct function though.

As far as I can tell the inversion isn't actually necessary. It also seems each "detent" on the wheel generates two counts.

( 19 August 2009 )

Got the jog wheel working with the AVRUSB code to send "frame advance/back" via the cursor keys in Blender.

code@rancidbacon.com