Project Proposal - WWU Electronic Engineering Technology

Nikolas Knutson-BradacETEC 471 – Project Proposal11.5.2012AMDRSSTC - Audio Modulated Dual Resonance Solid State Tesla CoilPage 1

Introduction:Drawing students into the STEM (Science, Technology, Engineering, and Math) field is focalpoint of higher education. As students commonly view STEM disciplines as mundane,institutions of higher learning look for unique and interesting tools to recruit students. TheAMDRSSTC is a multi-media spectacle that exhibits several STEM disciplines with a focus inelectronics engineering to prospective students.Project Description:The AMDRSSTC will consist of a resonant air-core transformer; IGBT half-bridge switching ahigh-voltage DC power supply; digital control system driven by current feedback; and amicrocontroller that translates a MIDI signal to enable output of the air-core transformer.The interrupter, that enables and disables the output of the system, will be centered around aMSP430 microcontroller. The interrupter will take input from any MIDI 1.0 device; thefrequency of the input signal will be the frequency of the output; the ‘key velocity’ of the inputsignal will determine the duty-cycle of the output signal. As to not drive the IGBTs of the powerbridge too hard the maximum on-time will be limited. The output of the interrupter willtransmitted through a fiber optic cable, this will render then output signal immune to the noisecreated by the ESD of Tesla coil.Page 2

The controller will consist of digital logic and two operational amplifiers that will read feedbackfrom two current transformers on the primary coil of the Tesla coil. One of these will be a zerocrossingdetector (ZCD) to keep the switching of the power bridge in phase with the coil. Theother will be threshold trigger, or an overcurrent detector (OCD); this will have a configurablelevel that when reached will disable the output of the system. The Interrupter, OCD, and ZCDwill feed into the digital logic that will drive a MOSFET full-bridge. The MOSFET bridge will feedinto a gate drive transformer (GDT) to control the power bridge. The controller will be poweredby a linear power supply, +9V DC For the MOSFET driver, +5V DC for the logic, and +24V DC for theMOSFETs to switch.The GDT is a 1:2:2 ferrite core toroid transformers, the two secondary winding will beconfigured so that the output of the two is inverted. These two outputs will each drive one ofthe two gates of the IGBTs in the power bridge.The power bridge is a half bridge centered around two IGBTs, these will switch power from thehigh voltage DC supply and feed it through the primary coil of the air-core transformer. In thepower bridge a low inductance layout will be critical as the operating frequency will in the200kHz range.The high voltage DC power supply will be made up of a full-wave rectifier supplying rectifiedwall voltage to a voltage doubler consisting of two large electrolytic capacitors, a largePage 3

smoothing capacitor, and Zener diodes will be used to smooth out ripple.There will be two current transformers; each will be comprised of two cascaded 1:33 ferritecore toroid transformers. The cascaded transformers get close to the desired turns ratio of1:1000, the actual ratio will be 33^2=1089.MIDI DeviceMIDI SignalInterrupterFiber OpticEnable SignalControllerFeedback120 V RMS In+5V DC +9V DC+24V DC LinearPower SupplyGate DriveTransformerCurrentTransformersVariableTransformerHigh VoltageDC SupplyPower BridgeTesla CoilTank Capacitor Primary CoilCoupledTop-loadSecondaryCoilModulated HighVoltageElectricalBackground and Benefits of Proposed Project:Stimulating examples of engineering projects are the best way to draw prospective studentsinto the field of electronics. Notable examples of electrical displays include, Tesla coils, Jacobsladders, Wimshurst machines, and Van der Graff Generators; these devices entice studentswith displays of high voltage. These devices serve as fine examples for demonstrating theproperties of high-voltage and are primarily hosted in physics departments.Page 4

The dual resonance Tesla coil, DRSSTC, is a solid state Tesla coil that uses semiconductors toswitch a DC voltage that serves as a driving force in a tank circuit. This is in contrast to astandard Tesla coil that uses a spark gap. The concept was created by Jimmy Hynes in the early2000’s, and was popularized by Steve Ward in 2005. Though this project can be implemented totransmit power wirelessly, the cost, size, and efficiency render it impractical, leaving the deviceto be used as an exhibition piece. The DRSSTC draws the eyes and the ears with electricaldischarges. As a DRSSTC is driven by solid state devices, this allows exacting control of thesystem; in particular modulating the electrical discharge into audio frequencies. The audiomodulated DRSSTC will be controlled by MIDI input modulating the electrical discharge to theMIDI signal input to it; this would allow the user to interact with the exhibit, enhancing theusers experience and interest in the field of electronics.Development and Demonstration:The production of the AMDRSSTC will use industry standard, logic, op-amps, transistors,microcontrollers, and passive components. Many components of the device will be speciallyfabricated; these include the air-core transformer, stand, enclosures, top-load, heat-sinks,power bus, and circuit boards.Due to the nature of the project having high voltage electrical discharge it must be enclosed forthe safety of the user. The enclosure will be approximately one cubic meter and constructed asPage 5

either a faraday cage made of a grounded structured metallic mesh or a non-conductivetranslucent enclosure made of a material such as Lexan or glass (though these would be costprohibitive.) The controller will be optically isolated and powered by battery, not only toovercome noise but for the safety of the user.Tentative Timeline:This project has been of personal interest to the developer and the construction of theprototype, with exception of the interrupter and the controller is mostly complete. Furtherdevelopment time will be focused in design and construction of the controller, coding of theinterrupter, design and construction of the enclosure.The projected completion date of the interrupter and software is 12.20.12The projected completion date of the controller is 01.01.13The projected completion date of the enclosure is 03.20.13This will allow an adequate time to troubleshoot all of the systems of the AMDRSSTC before thedeadline in June.Projected Cost:The projected cost of the project is $4782.50, is outlined and itemized in the attachedpreliminary bill of materials.Page 6

Toslink Fiber receiver N/A 757-TORX147LF,T 1 1.86 1.86Ferrite torroid 1" N/A 4 N/A N/ABridge rectifier 1.5A 100V 625-W01G-E4 1 0.44 N/AController subtotal: 24.00Tesla Coil4" PVC core 40" N/A 1 N/A N/AMagnet wire N/A N/A N/A N/A N/A1/4" soft copper tubing 15' N/A 1 N/A N/A3/4" plywood 8sqft N/A 1 N/A N/A1/2" threaded rod 4' N/A 1 N/A N/A1/2" washer N/A N/A 16 N/A N/A1/2" lock nut N/A N/A 8 N/A N/A1/2" nut N/A N/A 8 N/A N/A4" drain cap N/A N/A 1 N/A N/A4" aluminum ducting 6' N/A 1 N/A N/ASheet aluminum 25sqin N/A 1 N/A N/A1/4" brass bolt N/A N/A 1 N/A N/A1/4" brass nut N/A N/A 1 N/A N/Avarnish N/A N/A 1 N/A N/AAssorted fastners N/A N/A N/A N/A N/ATesla coil subtotal: 50.00LaborHoursPower section construction 8Tesla coil contruction 16Controller constuction 6Inturrupter construction 1Software development 20Project design 40Project troubleshooting 15Projected labor Total: 106Projected Total Cost CostMaterials 498.83Labor($30/hr) 3180.00Subtotal 3678.83Overhead(30%) 1103.65Total: 4782.50Page 8