headers that can directly connect to their components
with straight through cables (see the bottom of Figure 8).
This helps make the installation manageable.
A 5V power source connects to the 5VIN screw
terminal on the left side of the RG-2MtrDrvr PCB. This
power source drives both the RaspPi and the motor
circuits. A trace on the bottom of the PCB can be cut, and
a second power source connected to the MotorIn
terminal if using a higher torque stepper motor.
The two diodes, D1 and D2, provide bias protection
and isolate the motor noise from feeding back through the
power bus. To round out the general overview, you will
find a 5V piezo buzzer driven by Q4 in the top right of
the PCB (Figure 8).
Let’s now go a little
deeper into the core
LED Strip Circuit
At the bottom of
Figure 9, you see the
DotStar LED strip
connected to a flat
ribbon cable. This
cable plugs into a
“LEDstrp” on the
lower right side of the
shown in Figure 10.
LEDs are 5050-sized
LEDs from Shiji
APA102C. The LEDs
are on a flexible PCB
(LED strip) that are
driven with 5V. A two-wire SPI interface allows you to
send color and brightness commands to each LED in the
strip. That’s an easy task to bit bang through software on
Two transistors — Q1 and Q2, highlighted in the upper
left of Figure 11 — level shift the Pi’s 3.3V up to 5V for the
clock and data signals.
You’ll find an RG-LEDstrip Node.js driver at the article
link and/or at
https://github.com/RuckerGauge/RG-LEDstrip. This driver is a Node.js class that provides
20 December 2017
QTY PART MANUFACTURER DESCRIPTION
1 2237 Adafruit DotStar digital LED strip
1 2424 Adafruit Automotive gauge stepper
1 2448 Adafruit TB6612FNG 1.2A DC/stepper motor driver board
3 2157 Adafruit Quad alphanumeric display — white 0.54" digits w/ I2C backpack
1 1479 Adafruit 16 mm illuminated pushbutton — white momentary
1 400 Adafruit Wire housing pack
2 2N3906-AP Mouser 2N3906 transistors
2 CF1/4CT52R202J Mouser 2K resistors
2 CF1/4CT52R102J Mouser 1K resistors
1 CF1/4CT52R221J Mouser 220 ohm resistor
1 276 Adafruit Five volt/two amp power with 2.1 mm ID positive tip connector
1 610 Adafruit Panel mount 2.1 mm DC barrel jack
1 SB340-T Mouser 3A Schottky diodes
1 2243 Adafruit GPIO header for Raspberry Pi HAT - 2x20 short female header
1 39357-0002 Mouser 3. 5 mm screw-terminal block
1 3055 Adafruit Raspberry Pi 3 Model B
1 2693 Adafruit ScanDisk 16 GB Ultra Micro SDHC Class 10 card
1 400 Adafruit Extra long strip headers
■ FIGURE 9. LED strip.
■ FIGURE 8. Weather gauge RG-2MtrDrvr
daughterboard PCB layout.