What it does

The Reach sensor detects the proximity of an object by sensing the object's disturbance of an electromagnetic field. Once calibrated, the Reach sensor will produce a high output value with no object present. The closer an object is, the lower the value it sends to the I-CubeX Digitizer. The I-CubeX Digitizer converts this signal to MIDI messages according to the mapping you have programmed.

The Reach sensor only detects total amount of field disturbance not x/y position. The field exists on both sides of the panel, so it can be used vertically as well as horizontally.

How it does it

The Reach sensor creates an electromagnetic field that is toroid in shape, like a doughnut. When an object enters the field the size of the field is reduced, causing a smaller current to be detected by the I-CubeX Digitizer.

In the first diagram in Figure 1, no objects are disturbing the field and therefore the field remains at full strength. The second diagram has a hand placed above the inner circle which reduces the size of the field and hence a lower current is sent to the I-CubeX Digitizer.

Figure 1. Profile view of Reach Sensor. Electric field patterns: (A) No disturbance (B) A hand disturbing the field.

Tuning the Reach sensor

The Reach sensor detects objects due to their dielectric properties, which make it attract more or less of the Reach's electric field. However, all materials have different dielectric properties so that the Reach sensor has to be adjusted, using two parts on the sensor, to the object or material it is to sense.

Tuning Potentiometers (or Pots)

Only two parts are adjustable on the Reach sensor; the ZERO and the GAIN potentiometers whose location are shown in Figure 2.

Figure 2. Layout of tuning pots (top view).

Calibration Procedure

Follow these steps to achieve an optimal response from the Reach sensor:

1) Connect the Reach sensor to an I-CubeX Digitizer input; power the Digitizer and run the I-CubeX editor. Turn on a channel on the Programmer making sure it is set to receive the Input the sensor is connected to. Check that the Digitizer is sending sensor data (the green MIDI out indicator should continuously flicker).

2) Place the Reach sensor on the surface you wish to calibrate for.

Note: The Reach sensor requires a minimum 1" (2.5 cm) gap between the sensor and the surface ie.: table or wall. This is due to the Reach's electric field extending on both sides of the panel. Placing 1" of styrofoam under the panel works well.

The calibration setting is only optimal for the surface on which the calibration was performed on; for example, the calibration settings for a wooden table will differ considerably from that of a metal desk.

3) The first calibration involves finding the zero crossing. Set the GAIN potentiometer in its middle position and place the object to be sensed very close to the Reach sensor. Start the ZERO potentiometer in the most positive position and slowly turn the knob negative (counter-clockwise) until the sensor output just reaches zero. This is the zero position.

4) Remove all objects from the Reach and increase the GAIN initially so that the output becomes full scale. Note that the highest value output by the Reach will be about 96. Slowly decrease the GAIN (turn counter-clockwise) until the output value starts to drop. This is the optimal gain. At this stage of calibration, you should be able to move your hand toward the Reach and observe a decreasing output value.

5) The Reach sensor can start detecting objects from as far away as 6" (15 cm). To improve the Reach response, repeat steps 3 and 4 but move the knobs in small steps from their current position. Some tweaking may be required. If this doesn't improve the Reach sensitivity enough, investigate the surroundings. Metal objects above or below the Reach greatly reduce the performance.