From RoboJackets Wiki
Jump to navigation Jump to search

Despite being a fairly mature design, there are quite a few wrinkles in the kicker board. Furthermore, it seems to be much lower impedance than the last design and produces far more power (250V @ 360++A). This kills our silicon.

Current Limit

The current limit measures current through the silicon not through the solenoid. When using the circuit

  1. The IGBT switches on
  2. The IGBT switches off when a programmed current limit has been reached. Thanks to the flyback diode, that current still runs in the solenoid.
  3. Thus, when the IGBT switches on again (nearly instantaneously) it sees the current running in the flyback/solenoid + new current. This destroys the silicon

The solution is to measure the current running in the solenoid. I'll put up a modified schematic.

Also, there are a few problems associated with this section of the circuit

  • Shunt resistor is underrated. Burned up one during testing.
  • The gate resistors may have too little power though this is probably related to the failure of an IGBT during testing.

Barebones Layout Issues

The prototype was manufactured on a barebones process so some errors have been incurred as a result.

  • Traces running under isolated power supply can be shorted on mounting feet of supply

Mechanical Issues

  • Solenoid connector interfere with underlying screw
  • Battery connector interferes with underlying screw


  • Fuses soldered into holders
  • Jumper for the safe side logic power is far too large

Future Features

  • Space to add additional IGBT with separate gate drive resistor for each output
  • The ability to easily disable the current limit by removing or adding a part