Nice and cheep Product. The LDO is a LM6206, so the max input voltage is 6.5V. The board is based on a TLC555 and outputs a voltage from 3.3V to 0V. It consumes around 4mA at 5V or 3.3V. Wet soil gives a lower voltage than dry soil.

Nice and cheep Product. The LDO is a LM6206, so the max input voltage is 6.5V. The board is based on a TLC555 and outputs a voltage from 3.3V to 0V. It consumes around 4mA at 5V or 3.3V. Wet soil gives a lower voltage than dry soil.

Nice and cheep Product. The LDO is a LM6206, so the max input voltage is 6.5V. The board is based on a TLC555 and outputs a voltage from 3.3V to 0V. It consumes around 4mA at 5V or 3.3V. Wet soil gives a lower voltage than dry soil.

The sensor is based on an a-stable multi vibrator circuit using a 555 where the output duty cycle changes with the sensed capacitance. The simply over an RC circuit integrated signal is the board's output. Unfortunately, the discharge time constant on C (1µF) on this model (Ver. 1.2) seems very high (>10 sec) which is caused by too high valued or non existing discharge resistor. So I simply added a 1.2M resistor from the board's output to ground. There is just enough room at the connector side and already existing via's to easily solder a small 1/10W radial resistor on. This may slightly limit the output swing but gives more stable result voltages.

The sensor is based on an a-stable multi vibrator circuit using a 555 where the output duty cycle changes with the sensed capacitance. The simply over an RC circuit integrated signal is the board's output. Unfortunately, the discharge time constant on C (1µF) on this model (Ver. 1.2) seems very high (>10 sec) which is caused by too high valued or non existing discharge resistor. So I simply added a 1.2M resistor from the board's output to ground. There is just enough room at the connector side and already existing via's to easily solder a small 1/10W radial resistor on. This may slightly limit the output swing but gives more stable result voltages.

The sensor is based on an a-stable multi vibrator circuit using a 555 where the output duty cycle changes with the sensed capacitance. The simply over an RC circuit integrated signal is the board's output. Unfortunately, the discharge time constant on C (1µF) on this model (Ver. 1.2) seems very high (>10 sec) which is caused by too high valued or non existing discharge resistor. So I simply added a 1.2M resistor from the board's output to ground. There is just enough room at the connector side and already existing via's to easily solder a small 1/10W radial resistor on. This may slightly limit the output swing but gives more stable result voltages.