Powering Sensors from the dataTaker
The dataTaker is able to power sensors, relays, etc. from a regulated 5 Volt DC power supply terminal.
In the dataTaker 50 the 5 Volt sensor power supply terminal is located beside analog input channel 5, and is labelled +5V sw.
In the dataTaker 500/600 series loggers the 5 Volt sensor power supply terminal is located near the memory card socket, and is labelled +5V sw.
This power supply can source a current of up to 100 mA.
Caution : If more than 100 mA current is drawn from the 5 Volt sensor power supply terminal, then the performance of the dataTaker will be affected.
The 5 Volt sensor power supply is automatically switched OFF when the dataTaker drops to the low power or sleep mode.
The 5 Volt sensor power supply is automatically switched ON when the dataTaker is in the normal power or wake mode.
If the 5 Volt sensor power supply is used to power sensors when the dataTaker is powered by the internal battery, then battery life will be reduced.
The circuit schematic for the dataTaker 5 Volt switched power supply is illustrated below
Figure 10 ñ dataTaker 5 Volt Switched Sensor Power Supply
The sensor(s) to be powered from the 5 Volt sensor power supply are connected between the +5V sw screw terminal and any GND screw terminal.
The sensors are powered down whenever the dataTaker drops to the low power or sleep mode, and are powered up when the dataTaker wakes and powers up to the normal power mode.
If sensors powered from the 5 Volt sensor power supply have long warm up times, then a warm up delay can be introduced between the switching of the 5 Volt sensor power supply and the commencement of scanning of the sensors.
The dataTaker normally pauses briefly between waking, at which time the 5 Volt sensor power supply is switched ON, and commencing to scan the input channels. This wake delay can also be used to provide time for sensors to warm up.
This wake delay is defined to the dataTaker by the Parameter16 command in the range of 1 to 255 (See Section III ñ Parameter Commands). Parameter16 is specified in increments of 100's of mS.
Using DeTransfer, the command for example
sets the wake up delay to 3000 mS or 3 seconds.
The wake up delay can be set in the range of 100 to 25,500 mS or 0.1 to 25.5 seconds. The default wake up delay is 100 mS.
The currently defined wake up delay can be determined by the command
Small 5 Volt relays can be powered directly by the dataTaker, using the 5 Volt sensor power supply.
The relay coil is connected between the +5V sw screw terminal and the digital output channel being used to control the relay.