Shared Projects by dewhisna

NOTE: This board has been replaced by DRSSTC Bus Supply V1 and DRSSTC Bridge V2 as a modular pair.

Full-Bridge power circuit for running a small desktop Musical Tesla Coil from 110/120 VAC. This design features a Soft-Start power-up circuit and relay controlled power-off voltage bleeder circuit. Note: Soft-Start and power rectification circuits are NOT compatible with 220/240 VAC! Recommend using 2oz Copper.

This board is designed to be driven by the Dual-Resonance Solid-State Tesla Coil Driver board.

The debut performance for this board was during Shock-or-Treat Halloween 2018, and can be viewed at: http://mediadrop.dewtronics.com/media/media/shock-or-treat-halloween-2018.

Note: This board is still in the prototyping/testing phase and hasn’t been fully qualified yet. Build at your own risk.

ERRATA: Do NOT build this circuit as-is. The soft-start circuit has a design flaw that causes SCR (D29) to false trigger early and to “bounce”, which causes the Soft-Start Relay RL1 to chatter and fuse its contacts due to the high inrush current, ruining the relay. The high inrush current will then fry one or both mains input rectifier diodes D32 and/or D33, and then blow the fuse.

If building, do not install the following components: RL1, D29, D30, D31, R5, R6, R7, R8, R9, RV1, C2, and R14. In the place of R14, install a NTC Thermistor Inrush Current Limiter, such as Ametherm MS22-10008 (DigiKey: 570-1003-ND) – note that this can be installed between pads 41 and 44 of the RL1 footprint for closer pin spacing, but give it plenty of air space and ventilation, as it will get hot. You can also use a variac to slowly bring up power to the entire circuit – but you’ll need to start it at around 70 volts to keep the Bleeder Relay RL2 from chattering.

Also, resistor R10 needs to be a sufficiently high wattage part. It will have about a 155-160Volt drop at 3.3mA, which is 530mW. So, use at least a 3/4Watt resistor for R10 or risk it leaking its “magic smoke”.

Note that at circuit power-down, resistor R15 will get a little toasty. This is normal. However, your driving circuit should monitor the ‘fault’ pin (pin 3 of J1) and shutdown all AC input if the fault condition (i.e. Relay RL2 open) exists for more than a few seconds, as the 2.5W rating of R15 is only sufficient as a bleeder resistor for the system. A continuous load resistor of that value would have to be around 120Watts. If the 2.5W part was left in the circuit very long (longer than the required voltage bleed down period), it would either burn in two or catch fire.

Also, cut the copper-pour trace for the ground fill where it runs underneath the fuse holder. Failure to do this will cause a short between the 120VAC mains and ground under the 120VAC-input end of the fuse holder when the solder-mask gets breached beneath it. Apparently, I should have made the area under the fuse a keepout-area for that copper pour. It is, however, a self-correcting problem, because when it shorts, the trace, and select parts of the fuse holder, will vaporize. But it is a rather loud and startling bang, and you’ll probably have to reset the circuit breaker for your power feed.

Very Simple Musical Interrupter for driving dual Tesla Coils in stereo from Direct Audio. This is a custom variation of the original Dual VSMI 2.0 by Grégory Gusberti and Fabrício Franzoli as found on Alex Yuan’s website: http://www.personal.psu.edu/ahy5028/coiling/Schematics/Dual_VSMI.jpg. I built it to see how it compares with my other attempts at making a decent direct audio interrupter for Tesla Coils.

All ICs are TSSOP packages. All resistors and capacitors are 0805 footprint, with the exception of C6, C12, C13, C15, and C17, which are 1206. The LEDs are 1206 package. All thru-hole components (i.e. the connectors and potentiometers), plus the two LEDs, mount on the bottom side, which is designed to be the “top” in the final assembly.

To the original design, this version adds a headphone/speaker monitor output and fiber optic transmitters for driving a Tesla Coil control board. Reference designators have been kept in sync with the original schematic referenced above.

Errata: The 10K “Sensitivity” potentiometers, RV1 and RV3, operate backwards – turning them CCW increases sensitivity and turning them CW decreases sensitivity. Additionally, the Sensitivity potentiometers really do little to nothing at all, as the only time it will detect the incoming signal is if you crank the volume on your device to max and turn this circuit to maximum sensitivity. This seems to be a design flaw in the original circuit. So you might as well skip the Sensitivity controls and tie them directly to ground or do a fixed-resistor divider network like their other circuit variation at http://www.personal.psu.edu/ahy5028/coiling/Schematics/VSMI_REVB.jpg.

Also, the high-impedance DC-coupled pull-up on the inputs causes some phone/player type devices that use the bias/loading on their headphone jacks to detect connection/disconnection, to incorrectly think you have unplugged the cable from the jack. In other words, it can’t detect that this device is plugged in. My Android Samsung player device behaved that way.

Otherwise, it does function. The quality of the chopped audio, though, isn’t nearly as good as I had hoped. It’s comparable to several other attempts at a direct audio interrupter.

FPGA-Based Solid-State Stereo Musical Tesla Coil Interrupter interface board. Uses the Numato Mimas Spartan 6 FPGA Module to generate 512-note polyphony (256 per channel) Tesla Coil interrupter signals to drive two Musical Tesla Coils in stereo from MIDI and other audio sources at a 1.5625 MHz note-timer resolution.

It was originally designed to function with the Netduino Plus 2 host processor board, but will function with any Arduino R3 compatible host processor. It supports both 3.3v and 5v host interfaces with on-board level translators. Power can be supplied with 7.4v LiPo battery pack and monitored with on-board low-voltage detector circuit. This board includes a 4-button keypad connector and an I2C Interface circuit for connecting a 4x20 or similar character-based LCD screen (or other +5V I2C devices).

I built this to run two of the original v.1 old-style oneTesla Musical Tesla Coils running in stereo. I wanted something more hi-fidelity than their simplistic 2-note interrupter. I wanted an interrupter that you could actually play an entire orchestral piece through with complete fidelity, including pitch-bends and power level shift nuances. The only way to get enough capture-compare timers was to use an FPGA. I made the VHDL code for the FPGA available on OpenCores as Timer Output Compare Driver. Note: To access the source tree without needing an OpenCores account, click the “Browse” link next to the “SVN” label in the top left corner. The source files are in “timerocd/trunk/src/”, which can be built under the free version of Xilinx ISE. The prebuilt binary file is at “timerocd/trunk/xilinx/TimerOCD/TimerOCD.bin”, which can be loaded directly into the Numato Mimas module using the Python programming scripts on the Numato website.

Here’s a demo of the first prototype of this interrupter back when it was still running at 16-note polyphony on a single Tesla Coil: Amazing Grace on the Musical Tesla Coil. I don’t yet have a video of dual-coils on the new FPGA interrupter as I’m in the process of redesigning the primary windings to improve tunability (it isn’t perfectly tuned in this demo video – the arc should be even bigger!) and to try to alleviate some arc-over problems I’ve been experiencing (oh the joys of working with high voltage).

Final code for the host processor is still being developed.

This is Version 2 of the Arduino Compatible Interface Shield for interfacing with Blushless DC (BLDC) Motors having their own 3-Phase controllers with a PWM Speed Set Input. It supports either a two-signal 90-deg quadrature speed sensor or a 3-Phase Hall-Effect speed sensor input. It has support for either an optical reflectivity sensor or Hall-Effect sensor for Zero-Position/Index sensing or it can use an external Z-Pos Index Sensor if the motor already has one. Supports both 3.3V and 5V logic with on-board level shifters.

Unlike the original design, this version also adds an ATmega328PB (note: PB version, NOT ‘P’) coprocessor to control motor speed and provide a PID loop, which reduces the work overhead required by the main host processor on which this shield board is used. This processor is designed to communicate with the main host processor via I2C.

This version is the new replacement for the original https://www.oshpark.com/shared_projects/yW0aEBL9 design.

This is a K40 40W CO2 (Chinese) Laser to RAMPS Interface board. Similar to the “K40 Middle Man” board, but is more of a “K40 Middle Woman” – that is, it was created second and is more complicated, er uh, I mean more sophisticated.

Unlike the Middle Man board, this board drops all water pump and 12V routing signals, since it wasn’t relevant to my configuration. What it adds is (hopefully) better interface circuitry between the RAMPS and the K40 Laser Power Supply. The PCB footprint, however, was kept the same as the K40 Middle Man to be a physical drop-in replacement. Parts of this circuit was derived from the M2Nano control board on my laser and from its documentation from http://www.3wcad.com, including corrections to the commonly listed pin-out of the 12-pin ribbon cable connector, which generally is missing a second ground pin and a secondary YL (Y-limit) switch pin.

Interface Circuitry added over the basic trace routing is as follows:

1) Current limiting and voltage clamping on the X and Y axis limit switch inputs has been added. This is useful in case there’s a short in the ribbon cable between the endstop lines and the motor control lines. It would be better to fry a resistor or diode in this circuit than your entire control board stack.

2) A Laser Fire signal buffer has been added that filters it for noise, both with a simple low-pass filter and with a transistor circuit that requires a current flow instead of just a voltage change. It also uses the K40’s +5V line as its pull-up, allowing you to drop power to your RAMPS board (and its processors) and not accidentally fire the laser. This change does, however, require that you define “HIGH_TO_FIRE” in the Configuration.h file of your firmware when you compile it, as this circuit needs a high-signal to fire the laser.

3) A low-pass filter has been added to the Laser PWM output signal to make it more of a proper DAC signal to operate in place of the potentiometer on the K40 design. Presumably, the K40 laser’s power supply already has some filtering circuitry since others are getting away without using a filter, but this addition should help.

Any or all parts of the circuit changes are easily bypassed by omitting parts and/or adding 0-ohm jumper “resistors” in their place to get a simple “pass-through” board like the “K40 Middle Man”.

All surface mount resistors and capacitors are 1206 footprint. The schematic and bill-of-materials will be made available on GitHub, and linked here, once the circuit has been fully proven (i.e. once I finish my K40 Laser build).