manually. Using a PWB makes it a little easier, but not by
much. If you decide to use a different display with the
conventional 0.1” connector spacing, using standard perf
boards at a much lower cost makes sense. Your call! The
PWB artwork is also available at the article link.
There are two adjustments to be made at final
assembly time. First, R5 should be adjusted for the most
pleasing display appearance to you. Then, the battery
voltage must be calibrated.
With a new set of batteries
installed, set R3 so that the LCD
displays “12V.” That’s it. You’ll be
able to watch the effects of high
pulse widths and decreasing battery
voltage with age and use.
At this point, there’s not a lot to
add. However, the pulse width
deserves a little discussion.
The LEDs are bright enough so
that they will normally overcome
normal room illumination and be
sufficiently bright even at the
narrowest PW of 0.5%. If the
brightness isn’t sufficient, you can
increase the pulse width and get
However, as the PW increases,
resolution decreases. The fastest PW
(0.5%) means the LEDs are on for
0.5% of the time.
When a rotating device is being
visually stopped by the Stroboduino,
a PW of 0.5% means that the LEDs
are on for 360° x 0.5%, or 1.8° of
arc. This presents a pretty sharp
However, increasing the pulse
width to, say, 5%, means the LEDs
are on for about 18° of arc, causing a
decidedly smeared appearance. You
can decide how much PW you need,
and how much smearing you can
tolerate in the situations you
A Final Note
The StroboDuino times with the
flashes per minute rather than the SI
unit of Hz. This is because —
conventionally — motors are rated in
RPM, and FPM and RPM correspond
1:1. The StroboDuino takes it a step further with its display
and all its internal computations based on FPM. If you
need to convert back to Hz, 1 Hz equals 60 RPM (or
FPM), so conversion to Hz only involves dividing FPM by
A footnote to this is that if you choose to use a 16x2
LCD display, you’ll have space to put Hz on the display in
addition to FPM [ lcd.print(String(fpm/60, DEC));].
Now, go freeze something! NV
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October 2017 37