Blog Posts

Tachometer Using Photosensor

Elliot Carter published a tutorial on making a photoresistor-based tachometer.

The project came about when he needed to test the top speed of a stepper motor.  After putting it together the project became an important diagnostic tool for a larger project – not only does it test the top speed of stepper motors but it also works as a tool to verify code.

The tachometer measures rotational speed using only simple light sensor with an op-amp comparator circuit.  While many mechanical engineers might cringe at the thought of an op-amp, Elliot’s team found a tutorial that explained them well.

Fast pulse counting with interrupts and why nested priority really helps

A question was recently asked on the forum, how fast can attachInterrupt count pulses.  I did some testing to find out, and made this video.

Turns out Teensy 3.2 can run about 1.25 million interrupts per second.  Teensy 3.6 can do about 2.55 million per second.  But these depend on assigning a top priority to the interrupt, as explained in the video.

Of course, both boards can use a timer to count pulses at very high rates, at least 30 MHz.

Laser Ukulele

Marcus Herbert took an inexpensive ukulele, cut the strings off, designed some circuits, and turned it into a fully functioning laser ukulele that sounds great.

Some of the features include:

  • Custom tuning mode allows 128 notes as per the MIDI standard (12 notes [C, C#, D, D#, E, F, F#, G, G#, A, A#, B] across 11 octaves for C-G and 10 octaves for G#-B)
  • Full soprano ukulele fretboard (12 frets)
  • Four lasers as strings
  • Virtual capo can be placed along any of the 12 frets
  • Although this is in the shape of a ukulele, the computer software determines the final sound, so the physical instrument could end up sounding like whatever instrument you desire
  • Note velocity can be customized from 0 to 127 and is displayed on the LCD screen


Enchant Lightsaber FX Board

The Firebrand Forge has created an open source FX board (Kickstarter) for light sabers and other props.

UPDATE: This board appear to now be available on Tindie.


The ENCHANT board is a light and sound controller with an accelerometer and gyroscope.  It’s compact size makes it ideal for props, like light sabers, and wearables.

This video shows the light saber in action.

The rewards in their Kickstarter campaign include levels from an ENCHANT board, an ENCHANT wearable skirt, and multiple light sabers.




Cochlea Prototype For NeuroBytes

Zach Fredin made a cochlea prototype  – a human ear response for NeuroBytes neuron simulator system.

This video shows the prototype in action.

NeuroBytes are hands-on electronic neuron simulators that allow individuals to learn about the brain while physically building their own neural circuits, synapse by synapse.

Neuro Tinker has a Kickstarter in process for their NeuroBytes system.  The system is made up of modular neuron simulators that allow the user to build and simulate their own electronic brain.

NeuroBytes are fully open sourced,  All source files – schematics, PCB Layout, firmware, etc – are available and shared freely.

Atari 2600 Joystick to an iPad

Allen Huffman used a Teensy 2.0 as an interface between arcade joysticks and an iPad.

The project came about when he was having difficulty getting an expensive input board to work in a haunted house attraction.  When he discovered that the iCade keyboard commands worked over a USB connection, he figured he could use an Arduio board and hood the USB side to an iPad and create his own interface.  With a bit of research he got his project up and running.

Be sure to check out his forum post for details on how the project came about.  The code for the project is available on GitHub.