"Sherlock Breaker Circuit Breaker Finder"
Sherlock Breaker Circuit Breaker Finder ECE Senior Design I: Design Review Monday, November 22, 2004 Sherlock Breaker Team Members Kevin Fernandes Joel McCown (Team Leader) Receiver Hardware Website Documentation Transmitter Hardware Simulations Simulations Natalie Gilmore Derek Irby Documentation Receiver Software MS Project Documentation Simulations Dr. Noel Schulz Faculty Advisor Circuit Breaker Finder Components Transmitter • Plugs into 120V receptacle • Places identifying signal on line Receiver • Handheld, battery operated • Finds identifying signal Sherlock Breaker Abstract and Motivations To build an efficient Circuit Breaker Finder with the following major characteristics: • Operates on 2 AA batteries • Automatic sensitivity control • Multiple transmitters • Integration of older and newer technology Possible Transmitter Methods 1. Inputting a signal directly onto the line Difficult to have powerful multiple transmitters sending at different frequencies 2. Using a Voltage-Controlled Switch Relatively easy to create a detectable signal at the breaker Transmitter Overview LED 120 Volt AC Receptacle Pulsed Switch Circuit (SIDAC) Breaker Timing Circuit (RC) Silicon Diode for AC (SIDAC) 4 layers of alternating PNPN conductivity (emitter layer, upper base layer, mid-region layer, lower base layer) Emitter- One transistor Second Eventually, short circuit; Collector Peak begins transistor SIDAC remains at very Voltage conducting begins low impedance until Exceeded conducting current drops below holding value Left: Schematic for a Shockley Diode (a uni- directional SIDAC) Image courtesy of AllAboutCircuits.com SIDAC V-I Characteristics Transmitter Simulation Circuit Transmitter PSpice Simulation Sample output for one “pulse cycle” Transmitter Pulse Combinations Transmitter(s) on A B C A+B B+C A+C A+B+C the circuit Pulses received 120 60 40 180 100 160 220 at breaker Individual Transmitter Configuration A: 120 pulses per second B: 60 pulses per second C: 40 pulses per second Design Challenge: Sending multiple distinct signals without overlap! Transmitter Pulse Placement 2 milliseconds = 2000 microseconds between V-breakover and V-peak Line amplitude modulation through controlled, very brief short circuits Transmitter Prototype Results Test Set-up Portion of 60 pulses-per-second transmitter Prototype vs. Simulation for Multiple Transmitters Receiver Overview 1. Use a probe to detect various frequencies Design Challenges: simultaneously Multivibrator the receiver •Create a way to auto-calibrate Difficulties distinguishing accurately with low cost •Ensure the microcontroller can accurately distinguish and several pulses from multiple transmitters (needcount the noise and signal filters or powerful LED/ Pick-Up Coil Opamp microcontroller) PIC Buzzer •Supply receiver components with only 2 AA batteries! 2. Use a probe to detect induced current spikes on a line Peak Detector Digital Potentiometer Receiver Calibration Flowchart Peak Detector Select Calibrate Calibrate Read Signal Transmitter or Read Level A, B, or C Adjust Digital Read Potentiometer To Pulse Is Vout Counting too High? YES Peak Detector designed, but not fully implemented NO interface with PIC. to Receiver Calibration Testing Amplification Circuit Test Setup Receiver Pulse-Counting Flowchart Pulses Transmitter(s) Detected A 120 A+B 180 A+C 160 A+B+C 220 Receiver Pulse-Counting Testing Multivibrator Test Setup PIC Counting Test Setup 100 microsecond pulse length to ensure proper input to PIC Receiver Power Supply DC-DC Voltage Converter Reference Wiper Terminal Wiper Terminal 5V 2.5V Digital Pot Peak 1.5V Pick-Up Coil +/- Inputs Detector Op-Amp 1.5V Multivibrator PIC Voltage (not to scale) Prototype Residential Testing 120V Line Pickup Coil Time Works more accurately on newer breakers than older breakers Prototype Parts List Receiver Item # Price (each) Count Subtotal Pickup Coil 1 1.70 250 1.70 PIC 1 1.26 100 1.26 DC-DC Boost 1 1.04 1000 1.04 10K Digital Pot 1 1.01 100 1.01 Opamp 1 0.95 5000 0.95 Low Current LED 4 0.22 2000 0.88 2.5V Reference 1 0.35 1000 0.35 High Gain NPN 1 0.26 5000 0.26 1 Receiver + 3 Transmitters = Multivibrator 1 0.17 1000 0.17 Schottky Diodes 2 0.05 2000 0.10 Supply Capacitors 2 0.03 10000 0.06 Charge Pump Capacitors One-Shot Capacitors $17.29 2 2 0.03 0.03 10000 10000 0.06 0.06 Resistors 5 0.01 10000 0.05 Reference Input Capacitor 1 0.04 10000 0.04 Reference Output Capacitor 1 0.03 10000 0.03 Total 8.02 Transmitter Item # Price (each) Count Subtotal Capacitors 6 0.21 10000 1.26 SIDAC 3 0.30 5000 0.90 LED 3 0.16 10000 0.48 Fuse 3 0.07 1000 0.21 Resistors 12 0.01 10000 0.12 Rectifier Diode 6 0.02 10000 0.12 Total 3.09 Design Constraint Summary Met Partially Not Met/ Constraint Met Untested Applicable Line Voltages: 120 V X Transmitter Signal: 20A at no more than 3 X microseconds Environmental (power): 2 AA batteries X Economical (cost): Less than $80 X Manufacturability (size): Wait until SD II X Multiple Transmitters: Distinguish up to 3 X different transmitters Applicable Line Length: Accurate up to 300 feet X Safety: Use applicable fuses for UL Standards X Signal Strength Calibration: X Automatic calibration Reliability (accuracy and maintenance): X Testing in a variety of locations Future Developments Improvements to make in Senior Design II: • Third simultaneous transmitter • Automatic calibration • 3-way switch on receiver to select transmitter Acknowledgements • Dr. Noel Schulz • Dr. Lori Bruce • Dr. Herb Ginn • Dr. Raymond Winton • Jean Mohammadi-Aragh • Joel Martin • Odie McHann Questions? SIDAC Construction Left: Pspice equivalent model given by manufacturer Below: Example of a Shockley Diode (uni- directional SIDAC)