#Hold me closer tinyDancer!

*** COMING SOON

- Selectable base freqs to optimise the effect for objects with different resonant freqs

- Start / Stop input

Don't want to pay $200 for a Slow Dance time frame?
I don't blame you! And naturally, as a maker/hacker ... you build your own!

##Demo Video:

###Why is the Slow Dance time frame so expensive? One of the more expensive parts of that project is the microcontroller, for this the time frame uses an Atmel MEGA series chipset which is overkill to say the least! (most of the ATMEGA's peripherals such as I/O, timers and serial comms aren't used at all). This coupled with custom magnet coils seems to bump the price up quite a bit.

###So what microcontroller should we use? In order to bring the cost of building one of these down somewhat, the main functionality of slow dance has been implemented for a more suitable and much cheaper chipset, the ATTiny85, which can be had for as little as $1. Furthermore, by running the chipset with it's calibrated internal oscillator (as opposed to an external oscillator), tinyDancer can be run using just 1x LM7805 regulator and 2x TIP120 darlington transistors.

###Isn't that clock source inaccurate? It's true that the internal oscillator is only accurate to +/-10%, but given that the illusion is created by the relative difference in strobe frequencies, this error doesn't matter at all as the two signals remain 0.5Hz apart, and the overall error remains beyond human perception.

###So, how do I get started? The ATTiny85 can be flashed using any standard AVR programmer (no arduino bootloaders here folks), and I expect most will likely use the arduino ISP sketch to create their own programmer. If so the chip can be flashed using the following cmd:

sudo avrdude -F -c arduino -p t85 -U lfuse:w:0xe2:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

sudo avrdude -F -c arduino -p t85 -U flash:w:tinyDancer.hex

###Schematic

The TIP120 is overkill for the LED strip, however most vendors sell them in a pack of 2 or 3, so we use it to reduce parts/cost. The current limiting resistors currently limit the outputs to approximately 1A. The resistence of the coil I used was 18.6 Ohms. Using Ohm's law, that's a current draw of about 0.7A @ 12V. The TIP120 has an NPN gain of 1000X, so we only need to flow 0.0007A (7mA) to the TIP120 to barely activate the coil. Rounding this up for a bit of overhead to say, 10mA, we can solve the best suited resistor.

0.0010mA = (5V-0.7V)/R # 0.7V typical loss across PN junction.

=> R = 4300 Ohm. # closest being 4.7KOhm. Which would allow ~0.9A to flow from collector -> emitter

The same should be done to the LED line, currently the schematic uses the same configuration for the LED output. This makes the board a little more versatile in terms of customisation. For example the firmware could be altered to switch two opposing magnets rather than just one, then simply use another board for the LED output.

###PB4 strobes at ~90.5Hz (Magnetic coil via TIP120)

###PB3 strobes at ~90.0Hz (LED strip)

##Are there other ways to reduce the cost? Yup! Instead of buying 40ft of copper wire and winding it over a ferrous slug, simply repurpose a 12v solenoid by fixing the slug in place with epoxy (as close to centre as possible).

And if you want to go even cheaper, the LED strip can be of the solid PCB type, and you can make the frame and mounting out of questionable materials that you have laying around the house. Like I've done here :P

##Is there any part that shouldn't be cheap? Yes, throughout the build I noticed that you need a mounting (the part the viewing object is attached to) that has an appropriate amount of spring back and rigidity. For example, hack saw blades are too flexible, even when applied in two layers. The most successful mount I found was the iFixit 150mm steel pocket ruler. Though it's a bit long, it does the job well.

Another area of consideration is the rare earth magnets placed opposed to the coil. I found that the effect was a function of A. the distance from the coil to the mount, B. the rigidity of the mount as mentioned above, and C. The strength of the opposing magnetic field created by those magnets. So it makes the effect more tunable if you have a variety of magnets on hand. I ended up using the magnets found in a 3.5" HDD.