ConsolidateAmMeter project. The challenge: Build an Ammeter that will read the current of a given device and allow us to read how much voltage is being consumed by the device. Or in other words: We are building our own Kil-A-Watt. Why not just hack a Kil-O-Watt? They are digital and the computation happens inside a chip that is inaccessible when hacked Want to be able to capture data over a period of time: o In databases o Send to visual displays Why are we doing this? For the Green Room: Attach an ammeter to each device in the room to measure the usage and consumption of the devices over time. Have a display the changes based on the power being consumed o User sees one to one which device or combination of devices use the most energy. Collect data of energy usage over time o Determine which devices use the most energy or are used most often o Use data to determine how much solar/wind power is needed to take room off the grid For the Floor: Use ammeter to measure power consumption of 3 to 4 rooms on the floor Have a display the changes based on the energy usage of the floor Collect data of energy usage over time to determine which rooms use the most energy For the Electric Garden Measure the energy usage of various devices When devices are plugged in, the ammeters readings are used to trigger a visual display of the power consumption of the device The Research: Books: Practical Electronics for Inventors The Art of Electronics Articles: Analog-input circuit serves any microcontroller Active-feedback IC serves as current-sensing instrumentation amplifier Amp Meters and Current Monitors References/Documentation: RC Circuit Toms site Megans Photos - Flickr Angelas Photos Flickr Spiral Inductance Coil Calculator Capacitance/Freq/Inductance Calculator Air Coil Inductance Calculator Supply Outlets Analog device.com McMaster-Carr.com AMIDON.INC The calculation: Need to know the actual voltage of AC at ITP: Wattage to amperage: Watts = volts x amps For example: Two 60-watt lamps, and assume they're working at 120V: Watts = volts x amps 60 = 120 x amps So one lamp uses 0.5 amps in this case. Supplies: Chokes: One hacked from junk shelf Electric Current Indicating Rings from McMaster. (# 6570K6) Op- Amplifiers: LM386N TL082 741D JRC Why need the Choke? Detecting the Current Toroidal/Ferret Cores: Transformers Convert AC power at a certain voltage level to AC power at a different voltage, without changing the frequency The voltage induced directly related to the primary voltage by the turns ratio (N), o The number of turns in the primary coil divided by the number turns in the secondary coil. Split a wire of an extension cord and pass one wire of the cord through a choke AC passed through a copper wire; a magnetic field is generated around the wire. Second wire: corresponding AC is created within the second wire. A current is "induced" in the second wire. How to convert AC power to DC power? The Bridge A series of diodes that converts the AC power into DC power. The arrange is important to prevent the current from creating back flow The bridge alone did not provide meaningful data How to read the Current to Voltage? Yeah, we are still working on that one. Evolution of Circuit Issues The straight AC to DC diode bridge did not yield results that we can interpret The relationship between the known current of the device and the voltage readings are not making sense. Attempt 1 Op Amp LM386N Op- Amp was needed to get reading from the circuit LM386N Audio amp with a preset gain Determined that this may not be the proper amp meter to use Capacitors added to circuit to regulate voltage for better readings Attempt 2 opt Amp TLO82 TL082 Recommended 1 mega-ohm resistors Readings were 12 volts regardless of whether plugged in device was turned on or off Schematic of circuit Actual Circuit View Labeled image Attempt 3 switch inputs Switched the inverting and non-inverting inputs on the op amp from the diode bridge, removed the voltage divider Used Oscilloscope to read output Results not relating Input output 50W lamp @ 125VAC 2.64VDC 2 x 50W lamp @125VAC 4.8VDC 1 750W drill @125VAC 6.3VDC Attempt 4 trying new chokes Try new Chokes Suspect that choke may be the issue not the amp meter. Coil count unknown Find chokes with built to measure AC power AC power is 60 hertz. The current choke may not be built for 60-hertz range. Recommended we try AMIDON.INC for correct chokes Only one choke seemed to be made for the low 560 hertz range All others are for megahertz range Attempt 5 Use ardunio to gauge readings Working with Arduino to determine relationship of readings Attempt 6 Found Oscilloscope manuals To determine if using correct settings for readings Also a large resistor to control power o Large resistor did not seem to work |