After potting, the string should be tested to ensure the sensors are reporting correctly. Optionally and depending on your mounting needs, you can add 3M VHB tape to the back of the housing to allow for secure mounting without fasteners.
The testing step can and should be performed before potting as well to verify electrical operation before sealing.
Parts, Materials, and Tools Needed
- Fully-cured string assemblies
- 3M Very-High Bond (VHB) double-sided tape (optional)
- Pliers (for excess epoxy cleanup)
- Alligator clips
- 4.7 kΩ pull-up resistor (required — see callout below)
- Arduino with Firmware flashed
- Computer with a serial terminal (Arduino IDE, etc.)
Validate Operation
Prepare the Assembly for Testing
- Strip the end of the harness ~1.5 inches to expose the wires. Clip away the outer insulation and shielding, and cut the green wire.
- Strip the red, black, and white wires 1/4 inch.
- Connect the string to the Arduino with alligator clips: red to 3.3V, black to GND, and white to your data GPIO. Note: the One-Wire protocol requires the data line to be pulled to the supply voltage.
Pull-up resistor required
The 1-Wire protocol requires a pull-up on the data line. In most cases a 4.7 kΩ resistor between the white (data) wire and the 3.3 V supply rail will work, but for long cable runs, you may need a stronger pull-up (e.g. 2.2 kΩ) to ensure the signal is clean.
Read the Sensors
Open the serial terminal in your IDE. You may need to select a port — it will look like /dev/cu.usbmodem1101 or similar.
With the string connected, the program will cycle through readings from every sensor in the chain. Each reading should be between 15 and 25 °C indoors. The example output below is from an 80-sensor (4-board) string:
------------------ BEGINNING SCAN --------------------
Number of DS28EA00 sensors detected: 80
Converted Temperatures (deg C):
Sensor 1: 18.31
Sensor 2: 18.00
Sensor 3: 17.75
.
.
.
Sensor 78: 20.94
Sensor 79: 19.00
Sensor 80: 23.25------------------ BEGINNING SCAN --------------------
Number of DS28EA00 sensors detected: 80
Converted Temperatures (deg C):
Sensor 1: 18.31
Sensor 2: 18.00
Sensor 3: 17.75
.
.
.
Sensor 78: 20.94
Sensor 79: 19.00
Sensor 80: 23.25If every sensor reports a sensible value, the string is ready for deployment. Label the assembly, set it aside, and repeat for the rest.
Prepare for Mounting (optional)
Scrape Off Excess Epoxy
Inspect the backside of each string for any leaked epoxy. Snap off any blobs with pliers. Excess epoxy will keep the string from laying flat against the bonding surface and will prevent the tape from adhering.
Apply VHB Tape
Run a strip of 3M VHB tape along the entire backside length of the housing. Press it down with a paper towel or soft cloth to ensure it's fully set and free of bubbles.
