Handy Cricket Sensor Pinouts
If you'd like to wire your own sensors, here is the information you'll need.
The Handy Cricket sensor jack has three pins: the sensor signal line, ground, and a +5v supply.
The external sensor should provide a voltage between 0 and 5 volts on the signal line. The voltage is linearly converted into a reading between 0 and 255 (for 0 and 5 volts, respectively). If voltages outside this range are applied to the signal line, the Cricket may be damaged.
The Cricket includes a 47 K ohm pullup resistor from the signal line to +5v. This allows simple resistive sensors (like the touch switch and photocell) to be wired between the signal line and ground. The sensor sits in the lower half of the resulting voltage divider circuit.
The +5v line may be used to supply power to the external sensor device. In a stock Handy Cricket, this line is actually the unregulated 4xAA battery, so the voltage will vary between 4.5v and 6v depending on battery level.