• Fri 12-14 Progress Log

    jdunbar360 • 12/15/2018 at 21:58 • 0 comments

    What got done:

    • Measured frequency of LC tank with oscilloscope 
      • Unloaded work coil oscillated at 95.2kHz with 2uF capacitance
      • With two more capacitors (2.64uF total) the LC tank resonated at 83kHz
      • 9 capacitors gave 77kHz and 10 produced 71.4kHz
      • Frequency dropped by a few kHz with a load on the work coil
    • Calculated the inductance of the work coil to be 1.43uH (from capacitance-frequency measurements)
    • Measured current draw of induction heater from 24VDC power supply
      • Unloaded: 4.5A for 110W without object in work coil
      • Loaded with small ferrous object: current jumps to 6.4A and rises to peak at 8.3A (200W) before slowly dropping as metal object heats up
    • Began building MultiSim model of circuit using experimentally determined work coil inductance

    Issues:

    • Work coil still gets excessively warm while running for longer periods of time; may lose structural integrity.  We plan to solve this issue by running for short periods of time or adding fans.

    Next steps:

    • Continue MultiSim modeling to compare theoretical to experimental results
    • Test other metals for their behavior in the work coil

    Heating a large nut to cherry red heat using eight capacitors:

    Oscilloscope measuring 2.64uF LC tank voltage (after a 10x voltage divider):

  • Thurs 12-13 Progress Log

    jdunbar360 • 12/13/2018 at 21:50 • 0 comments

    What got done:

    • Soldered on the chokes and finished the capacitor board
    • Formed the work coil and soldered it to the board
    • Connected the power supply to a switch and connected it to the driver circuit
    • Connected an LED to show when the circuit has power
    • Did initial testing with iron, achieving roughly 1000  degrees Fahrenheit in a short period of time

    Issues:

    • A power supply wire pulled away from the copper clad board, meaning we had to move our circuit around a little and re-solder for sturdier connection
    • Our work coil reaches very high temperatures, especially with object being heated.
    • Capacitor bank gets hot with prolonged use

    Next steps:

    • Part-Sim theoretical testing
    • Possible future testing with varied capacitance

                              Bottom of the circuit

          Top-down view of circuit

  • Wed 12-12 Progress Log

    jdunbar360 • 12/13/2018 at 15:49 • 1 comment

    What got done:

    • Soldered in fast diodes
    • Disassembled premade choke assemblies to improve utility
    • Bent and soldered in LC tank copper busbars (made from 14AWG solid copper wire), with connections available for work coil
    • Soldered in 4 out of 6 initial capacitors for cap bank
    • Sourced wire for work coil

    Issues:

    • Component side of board is crowded with crossed component leads; must monitor and inspect to avoid shorts
    • Unconfirmed, but chokes may be wound with too thin of wire for the level of current they will be handling

    Next steps:

    • Solder on chokes and two more capacitors
    • Form work coil and solder on
    • Add power connectors
    • Solder in power LED and its current-limiting resistor
    • Test!

    Current state of the board, with four capacitors soldered on capacitor bank:

  • Tues 12-11 Progress Log

    jdunbar360 • 12/13/2018 at 15:36 • 0 comments

    What got done:

    • Soldered in Zener diodes, power resistors, 10K resistors
    • Connected MOSFETs to central negative rail
    • Created heavily-soldered rail for each MOSFET connection to positive
    • Added solder to board to buik up positive rail

    Issues:

    • Difficult to connect copper pads with solder on board to make a continuous rail; solved by laying piece of solid-core wire across pads to facilitate connection
    • Extra length of resistor leads were used to bridge gaps between copper pads

    Next steps:

    • Solder on more components
    • Form work coil
    • Create bus for capacitor bank
    • Make connectors for interchangeable work coil
    • Add power connectors

    Shown below, solder trace side of board and MOSFETs:

  • Mon 12-10 Progress Log

    jdunbar360 • 12/10/2018 at 21:35 • 0 comments

    What got done:

    • Checked power supply for outputting correct voltage unloaded and under 590 ohm power resistor load.
    • Inventoried and checked over all parts in BOM.
    • Planned out part locations on protoboard
    • Soldered in MOSFETS as most important element in circuit

    Issues:

    • Small board size is good for part stability but bad for routing traces.  Need to be creative with arranging high-current traces

    Next steps:

    • Solder on more components
    • Create high-current traces by adding solder to protoboard
    • Create bus for capacitor bank
    • Make connectors for interchangeable work coil