Knock Knock Puzzle by Dark Tech Effects
Options for Puzzle:
1. NC or NO Solution – Do you want the puzzle to turn on or off the output voltage to the solution
terminals when the puzzle is solved?
NC – Provides power until the puzzle is solved then turns off power
NO – Provides no power until puzzle is solved then turns on output power.
This feature allows for two different situations. When using a mag lock you will want it in the NC
position, when using a light or controlling a larger system you may want to use it in the NO position. The
puzzle is in the NC position when the blue LED is illuminated, and NO position when the blue LED is not
illuminated. Press the switch labeled “1.” To switch between NO and NC positions. You can check the
output voltage across the terminals labeled “4.”
2. Output voltage on the solution terminals – The larger slider switch labeled “2.” Allows the user
to select the output voltage that will go to the solutions terminals. The two options are 12V or
24V DC. Select the appropriate voltage for your mag lock, lights, etc.
3. Delay – When the puzzle is solved, the dial labeled “3.” Will allow you to configure the output
on/off time between 1 second to 4 minutes.
4. Solution Output – Wire your mag lock, light, or other 12 or 24V DC device to be turned on/off
when the puzzle is solved. Pay attention to polarity so as to not damage your device. There is
Pwr (+), and Gnd (-) terminals labeled on the board.
5. Knock Sensor Terminal – Connect the wires of the knock sensor to this terminal block. Polarity is
important, so ensure the red wire goes into the “+” side of the screw terminal, and the black
wire goes into the “-“ side of the terminal. You can use the gray terminal block to easily extend
the wires from the provided knock sensor. If you choose to extend the wires using the terminal
block, we recommend you braid the wire extensions between the gray screw terminals and the
enclosure. Braiding the wire extensions helps to reduce noise in the system which provides a
more reliable knock puzzle.
When mounting the provided knock sensor (#11) to a surface, use the screw mounts to securely
fasten the sensor onto the surface. It is important the sensor rests flat and securely against a
hard surface. Tape is not sufficient to mount the sensor.
6. Power Supply – Plug in the proved 12V power supply here. This powers the electronics board as
well as the output voltage. There is no need to use a second power supply for your mag lock or
lights unless your system requires more than 2 amps (24 watts). It is recommended that you use
the power supply included with your purchase. However, if you require using a different power
supply, it is important to use one that has a third prong into the outlet. This provides an earth
ground which reduces electrical noise in the system.
7. Puzzle Solved LED – This light will illuminate to indicate when the puzzle has been solved. It will
remain illuminated for the entirety of the time for which the puzzle state is “solved”. This time is
set through the dial from section 3.
8. Power LED – This red light will illuminate solid when the board is receiving power and the puzzle
is turned on. If the red LED is not on when plugged in or flashing, there may be an issue with
your puzzle.
9. Knock Detected LED – This blue LED will blink when a knock is detected. Use this LED when
programming your puzzle to ensure the puzzle correctly identified a knock.
10. Programming button – The red button is used to program the “solution knock” to the puzzle.
See the programming instructions for more details on programming a new knock. When the red
button is depressed, a yellow LED will illuminate solid.
11. Knock Sensor – Screw or glue the sensor into a hard surface to properly detect knocks. Tape
most likely will not be sufficient for attaching the sensor to a surface as unexpected movement
of the sensor could lead to misread knocks. The sensor should be mounted behind the expected
knocking region. This sensor works by detecting small vibrations in a hard surface, it does not
detect sound. Vibrations in the knock puzzle are sent to the microcontroller as electrical pulses
which are analyzed by the microcontroller.
Programming Instructions
Upon receiving the puzzle you must program an initial solution. This is done by performing the desired
knock while holding the red button mentioned in item 10 above. After releasing the red button the
solution LED and knock detected LED will blink two times to indicate the knock pattern was stored.
Upon restarting the puzzle the previous knock solution will remain the valid solution. Each time you
reprogram a solution, the previous solution will be erased and the new solution will remain in
permanent memory.
Knock Patterns
Knocks stored within the puzzle are stocked as relative delay times between knock sensor
measurements. That means your pattern must have at least three knocks. After all knocks are
recognized, the onboard microcontroller stores each delay as either a short knock or a long knock. Long
and short knocks are identified based on the relative delay time between any given knock and the
longest or shortest knock in a pattern sequence. This way, knock pattern solutions can be described as
any pattern of long and short knocks, potentially drawn as a “*” or “–“ where the absolute delay
between knocks indicated as a “*” or “–“ does not matter.
As an example to the use of relative knock patterns described above, say a knock pattern was described
as * * – * –. One user may interpret “*” as a 1 second knock, and “–“ as a 2 second knock, while another
may interpret “*” as a 0.5 second knock and “–“ as a 3 second knock. Both would be equally valid for
programming or solving the puzzle. In this fashion you can also use a “Morse code” knock/clue as that
would work perfectly to solve the puzzle. An example would be giving either a word or letters to spell
out with knocks in Morse code.