OpenTag OpenTag3 User manual

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Open Tag3 Manual
Overview
OpenTag3 records motion sensors at 50 Hz, and depth, temperature, light, and speed sensors at 1 Hz to
CSV files. Files are 1 hour long by default. There will be a short gap between files. OpenTag3 supports 32
GB or smaller microSD cards.
OpenTag3 is open source. Software is located at https://github.com/loggerhead-instruments/OpenTag3
•Accelerometer, Gyroscope, Magnetometer (MPU9250): 100 Hz
•Pressure/Temperature (MS5837 or Keller PA7LD): 1 Hz
•RGB light level (ISL29125): 1 Hz
•Burn wire release: controls a FET switch to ground which can be used to corrode a stainless steel
wire in seawater

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Quick Start
1. Setting Time
The time is set by saving the setup.txt card with a date and time, ejecting the card from the computer, and
inserting the card into the OpenTag board. When the time stored on the card occurs, the power switch
should be turned on to set the time on the clock.
Once the time is set, as long as there is charge left on the battery, the current time will be retained (even
with the power dip switch off).
2. Starting Record
Insert the microSD card in the recorder. The card holder is flip top: slide and flip up.
To start recording, slide the dip switch to the ON position. The recorder will set the time if present in the
setup.txt file and start recording.
3. Stopping Record
Press the Stop button located inside the ring. After the red LED turns on solid red, turn off the power
switch. If the DIP switch is not turned off in 30 seconds, recording will resume.
OpenTag3 LED Startup Sequence
Red LED
Green LED
Description
Solid On
Flashing
Green LED flashes for current hour (e.g. at 09:40 it will flash
9 times). Used so you know time is set approximately
correctly.
Off
Solid On
Sensor initialization. Camera should power on with red LED
underneath on DVR illuminated (you can see from side of
tag)
Flashing
Flashing
Flash simultaneously 11 times, to give camera time to boot.
Off
Blink once per second
Recording

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Example setup.txt File (set time to 10 April 2018 at 1 PM; Trigger burn after 400 minutes)
// Set Time
TM 18-04-10 13:00:00
// Set burn in x minutes
BM 400
setup.txt Commands
setup.txt should be saved in root of microSD (not in a directory)
// Indicate lines that are comments. Any line with // will be ignored
Command
Function
Example
TM
Sets time (YY-MM-DD hh:mm:ss)
TM 18-04-10 13:00:00
BM
Burn in mmm minutes from start
BM 60(burn 60 minutes after power on)
LD
Disable blinking green LED
LD
HE
Enable Hall Sensor to Trigger Red
LED (for testing)
HE

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Charging
The lithium battery can be charged by connecting a microUSB cable to the OpenTag3 and a PC or other
charger.
When charging the red LED will be on. When charging is complete the LED will turn off. Charging will
typically take less than 10 hours.
Power
Tags can be supplied with either 1 or 2 lithium polymer rechargeable batteries (2500 mAh).
Run time with 1 battery is approximately 7 days.
Run time with 2 batteries is approximately 14 days.

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Burn Wire
A burn wire is a corrodible stainless steel wire that can be used to release the AMX from a platform or
release suction from suction cups. The recommended wire is from McMaster-Carr (302/304 stainless steel
wire 0.01” diameter). https://www.mcmaster.com/ - 6517k61/=17yvpwx
The timing of the burn wire start is controlled by the BM command in the setup.txt file.
1. Run wire through one of the holes in the mounting plate, and start screw in side. Wrap
excess wire around screw.
2. Attach mount plate to tag and wrap wire around center post. Screw down acorn nut to hold
wire in place.
3. Run wire through opposite side of plate and insert screw to tighten down. Wrap around
screw a few turns. The burn wire should be taut to help it break when it starts to corrode.
Cut off excess wire.

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VHF
If your AMX has the optional VHF, it will turn on based on the depth or the status of the burn wire. If the
depth is deeper than 1.0 m, the VHF will turn off. The VHF will be turned on and stay on after the burn
wire is triggered.
Depth Sensors and Maximum Depth
The OpenTag3 is equipped with one of two types of pressure sensors, each of which has a maximum depth
that it can sustain. If the tag could go deeper than 300 m, the air void where the microSD card is located
should be filled with mineral oil. Mineral oil is non-conductive, and will keep the cap from imploding if the
tag goes deeper than 300 m.
TE Connectivity
30 Bar (300 m max depth)
Keller
200 Bar (2000 m max depth)
Or other sensor as specified.

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Sensor Calibration
All sensors used on OpenTag are digital, in that they have their own analog-to-digital converter. The
values stored by OpenTag are calibrated using the calibration values supplied in the technical specification
sheets.
Example data file:
accelX
accelY
accelZ
magX
magY
magZ
gyroX
gyroY
gyroZ
date
red
green
blue
mBar
depth
temperature
spin
V
42
105
-2014
226
-202
-246
54
44
0
46
105
-2008
231
-203
-247
51
41
-2
44
107
-2016
230
-204
-238
52
43
0
48
107
-2007
231
-207
-249
50
44
0
41
107
-2012
227
-207
-245
53
44
-1
43
109
-2004
227
-211
-239
52
43
-2
42
109
-2006
235
-205
-249
52
45
0
18-04-22T010:28:17Z
1476
1539
839
1008.41
-0.01
24.53
0
3.69

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Sensor Calculations
The IMU data (accelerometer, magnetometer, and gyroscope) and RGB light sensor data are stored as 16-bit
integers. They need to be multiplied by a calibration factor to get appropriate units.
The pressure data are stored as mBar and a depth calculation is performed assuming saltwater (111.377
mBar/m) and a surface pressure of 1010.0 mBar.
The temperature data are stored as degrees Celsius.
Spin is the number of rotations of the impeller per second.
V is battery voltage.
Date is the date and time from the real-time clock and assumes the time was set to UTC.
Sensor Calibration Factors: Multiply the sensor values by these values
Sensor
Calibration Factor
Units
Accelerometer
16 g / 32768 = 0.00048828
g
Magnetometer
4800 uT / 32768 = 0.146484375
microTesla
Gyroscope
1000 deg/s / 32768 = 0.0030517578
Degrees / second
Red
20 uW/cm2/ 65536 = 0.003051758
microWatt/cm2
Green
18 uW/cm2/ 65536 = 0.000274658
microWatt/cm2
Blue
30 uW/cm2/ 65536 = 0.000457764
microWatt/cm2

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Making a Recording for Gyroscope Calibration
Note that when the tag is recording without moving, the gyroscope should have values of 0
degrees/second, but there is typically an offset.
Place device in a known orientation for a few seconds when recording starts. Generally a flat surface is a
good idea.
The values for the gyroscope from this offset calibration recording should be averaged for each axis, and
then subtracted from data collection files.
X Gyroscope offset = mean (gyroX)
Y Gyroscope offset = mean (gyroY)
Z Gyroscope offset = mean (gyroZ)
Making a Recording for Magnetometer Offset Calibration
The purpose of the magnetometer calibration is to record data from all possible orientations. This is used
to correct for offsets in the magnetometer due to nearby metals. For the first recording, rotate the device
in all possible orientations (both horizontally and vertically). Put on some LMFAO and do some shufflin'.
These data can be used to determine the offset caused by nearby metals in post-processing.
The values for the magnetometer from this offset calibration recording should be analyzed by finding the
minimum and maximum values for each axis. Subtract these offsets from the X, Y, and Z magnetometer
channels.
X Magnetometer offset = (max(magX) –min(magX)) / 2
Y Magnetometer offset = (max(magY) –min(magY)) / 2
Z Magnetometer offset = (max(magZ) –min(magZ)) / 2

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Revision History
23 April 2018 Initial Manual