Thunderbolt Monitor Kit Manual v5.0.6
Page 4
3/8/2020
not be directly connected to an LED, a series resistor is required. The open
voltage is 3.3V when the alarm is active, 0V when not. The current capability is
about 10mA. A 330 Ohm series resistor will therefore be the lowest value
practical to drive an LED. Most LEDs give sufficient brightness with 3 to 5mA,
therefore a 1 kOhm resistor should be adequate in most cases (see wiring
below.)
5) J6 pin 1 has a square solder pad, visible from the solder side. Pin 1 is at the end
near SW1.
6) D1 turns on when the WiFi module is associated with an access point
7) D2 blinks when the WiFi module is connected to a PC running the Lady Heather
software.
8) D3 blinks at a one second rate to indicate power is applied to the kit.
9)
See thermistor wiring below
Pinout:
Note about the optional thermistor: A suitable part number is the Murata
NXRT15XH103FA1B040 available from Digikey. With this thermistor, the external
temperature display’s accuracy will be better than 1°C between 25°C and 50°C.
Features:
Display:
The kit is provided with a connectorized, backlit 2x16 LCD display, allowing the user to
easily replace the stock display with a different device that is compatible with the very
popular Hitachi HD44780 specification.
Backlight intensity is controlled by resistor R7 (the only leaded resistor on the kit, located
near the right end of the LCD connector.) The default value is adequate for use with
relatively low ambient light. Bypassing R7 with a short jumper wire will increase the
brightness (and the current consumption) and will make the display more visible in
brightly lit areas.
