run the line to where it’s located.
■ FIGURE 20. The pill bottle pushbutton
switch ready for assembly.
Synchronized Sound Effects! — You
can add a serially controlled
sound effect unit such as the CAR
P300 Audio Board kit from the Nuts
& Volts store. This will allow you to
trigger just the right sound when
your prop drops! Make a scary synchronized scream,
play a Happy Birthday tune, play the graduation march,
or launch into a Christmas carol to accompany just about
any surprise reveal.
to activate your Prop
■ FIGURE 21. Female RCA jack
mounted on the pill bottle cap
ready for connection.
Add a Limit Switch — Rather than using the timed retrieve
method, it's possible to place a marker or device to
indicate that the prop has been completely retrieved. One
implementation would be to use a lever switch and a
bead on the string. Cut a hole in a Popsicle stick, then run
the drop line through the stick. Write a process that
continues to loop waiting for the switch closure before it
stops winding up the prop. This would allow different
string lengths without having to re-program the chip with
new winch time values. It would also allow a consistent
retrieve distance even if the string stretched a bit with use.
Add a Variable Time Control — By adding a small potentiometer and using the POT command in PBASIC, you
should be able to adjust one of the values of the device
on-the-fly. For example, you could adjust the amount of
time for the hold off or the length of time the prop is left
dropped before it's wound back up. By changing some of
the hard-coded values to POT created values, you could
adjust for line length without having to build a limit switch
or adjust how far you prefer the prop to retract after use.
Use RANDOM to Create Variety — Use the RANDOM
function to have the Prop Dropper dispense a different
surprise on each trigger or to have it set a random hold off
value. The random function can be used in various ways
to alter the device's deployment to make it less
predictable, especially if you're using the motion sensor
The Prop Dropper now in KIT FORM!
Due to some fancy footwork from the folks at EFX-TEK
and the good folks over at the Nuts & Volts Store, you can
get a complete kit of parts to make your very own Prop
Dropper. This is great if your junk box is a little light on
parts or if you don’t have the time to scrounge around for
stuff. The Prop Dropper kit includes both a continuous-rotation and a standard servo, as well as the Prop-1 unit
from EFX-TEK. All you need to do is spend a bit of time
assembling it with a hotmelt glue gun and you should
be ready to go! The Prop Dropper kit is a fantastic
foundation for more experimentation in special effects.
A kit can be purchased online from the Nuts & Volts
Webstore www.nutsvolts.com or call our
order desk at 800-783-4624.
As you can see, with a little imagination the Prop
Dropper can become a very fun and useful little gadget to
have around. I hope you build one and use it. If you do,
please write and let me know how it went. I can be
reached at firstname.lastname@example.org. NV
PARTS LIST FOR THE PROP DROPPER
QTY DESCRIPTION MANUFACTURER
1 Prop-1 Controller Board EFX-TEK 31101 or equiv
1 PIR Motion Sensor EFX-TEK 555-28027 or equiv
1 4” Extension Cable EFX-TEK 805-00035 or equiv
1 Continuous-Motion Servo Parallax 900-00008 or equiv
1 Futaba 3004 Standard Servo SparkFun ROB-09064 or equiv
1 Wirenut Home Depot 30-072 or equiv
1 Prop to drop Oriental Trading IN-25/1258
October 2009 57