will tell you the forces involved. With drones all the rage
now, how many gs can they pull?
The trip mode allows the user to set the tripping
threshold from 0 g to 15 g. The data collection rate —
along with amount of time recorded — is programmable.
The sensors measure 3 x 3 mm. The lower g sensor
cost is minimal — around $3. They are quite difficult to
solder, however, and there is no use in ruining the larger
board which holds the microprocessor and SD card. I
mounted the sensor on an eight-dip header (Figure 4).
If you wonder why the chips are so inexpensive, they
are mass-produced for handheld computers and detect if
they are shaken, jarred, and rotated or tapped just by
utilizing g forces. They use two capacitors with a plate in
between and measure the change of capacitance between
The LIS3DSH has an analog to 16-bit A/D (
analog-to-digital) converter and transmits the data using the I2C
protocol. By using the two’s complement, it gives positive
or negative g forces. The first 15 bits give 215 = 32,768
bits of information. The 16th bit changes the sign, and the
following data bits are another 32,768 bits of information.
The unit has a built-in clock which is programmed
with the SD card. There is a power switch and pushbutton
switch that program the unit. A bi-colored LED acts as an
indicator for programming.
When the g force exceeds a predetermined amount,
it starts the recording and indicates by a flashing LED that
data has been collected. The unit draws 1 mA when in
sleep mode. Two AAA batteries will provide power for
34 November 2014
ITEM QTY DESCRIPTION SOURCE/MODEL NOTES
Battery Holder 1 ea Two AAA batteries
C2 1 ea 10 µF 16V
C3 1 ea .1 µF 100V
C4-C5 2 ea 33 pF 100V
Header 1 10 ea .1 vertical male
Header 2 10 ea .1 vertical female
IC2 1 ea PIC24FJ64GA002 Microchip
R7 1 ea 330 ohm 1/8 watt
R6-R8 2 ea 10K 1/8 watt
R9-R13 5 ea 10K 805
S1 1 ea SPST tactile red Tl1105F250Q E-switch
S2 1 ea SPST slide switch EG1903 E-Switch
SD Holder 1 ea SD-I/O memory card holder 0678408001 Molex
T1 1 ea Bi-colored LED
X1 1 ea 32.768 kHz 6PF CYL
2-16 g LIS3DSH accelerometer mounted with capacitors Nuts & Volts Webstore
100-400 g H3LIX331DLTR accelerometer mounted with capacitors Nuts & Volts Webstore
STEPS TO USE THE WINDAQ
Getting rid of the header:
1. Insert the SD card into your computer.
2. Open the file in Excel as described in the text.
3. Remove any header and date.
4. Remove blank cells by using “Delete Sheet Rows.”
5. Save the file with a different name (as a txt file).
Putting your Accelx.txt file into WinDaq:
1. Open the WinDaq Waveform browser.
2. The screen will flash “WinDaq Waveform Browser”
and then “WinDaq Playback Open.”
3. Change the file type to txt mode.
4. Load the file which you just named.
5. Click on Open. The text file will need to be converted to
a wdc file, e.g., Seis1.wdc.
6. Use a spreadsheet file.
7. Rename and save. A new black screen will open. In the
center area, it will probably display “Translating 3
Channels” of data.
8. Press return and the graph will pop up.
Using the Graph:
1. Click on Options, and then click on Cursor Time.
2. At the bottom of the screen, the time and date the data
was collected will display.
3. If you place the cursor under the black line and below
the last red line, you will be able to read the number of
seconds since the start.
4. Use the keyboard arrow keys to see the rest of the
■ FIGURE 4.