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ionpak-thermostat/hardware/errata.md

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Hardware errata

Rev 1

  • R307 needs more clearance from D400
  • Pins 1 and 12 of U502 need pull-downs
  • Pin 1 of U501 needs pull-up
  • D203 reversed polarity
  • R236 and R234 are swapped
  • Q301 needs to be NPN, change to BC817
  • increase R307 -> 3.3Kohm and increase R500 -> 33Kohm
  • C201: oscillates at 0 and 1nF, stable at 100nF
  • add clamp diodes to GND on op-amp outputs to ADC when op-amp has negative supply
  • R214 -> 7.5k
  • LM339PT is in TSSOP package. Change for SOIC P/N
  • GDT200 minimum firing voltage is too low
  • the relay model should be changed to 9001-05-00. 9001-05-02 is an undocumented normally closed variant.
  • D504 should follow the schematics in its datasheet
  • R502 should be connected to VCC
  • R502 -> 240 ohm
  • C500 -> 1nF
  • R234 -> 7.5k
  • Q104 -> DMN3404
  • R114 -> 470 ohm
  • R115 -> 4.7k
  • R227 -> 470 ohm
  • R228 -> 4.7k
  • review values of R226 and R113
  • C100 -> 47pF NP0 AVX, R107 -> 100K, C101 -> 0.1uF
  • use crystal type recommended by the MCU datasheet
  • add connector for OLED display?
  • enlarge holes to fit M3 screws comfortably
  • add 15M resistor between A and FIL-
  • power U200 from a small negative voltage instead of GND
  • review choice of filament flyback output diode
  • invert LED position so that the Ethernet LED is closest to the connector
  • invert polarity of LEDs (Ethernet LED polarity cannot be programmed)
  • change D351 model to MBR1645
  • add snubber on D351
  • add heatsink (Seifert-KK633) to D351
  • move D351 further away from transformer for heatsink clearance
  • add plated-through holes and pads for mounting rods of BNC connector
  • simplify FBI circuit, 2 ranges only (typ. 8mA and 45mA), remove diodes and neglect MOSFET leakage
  • to support different case designs, replace the holes on the connectors side with slots. One of the case designs requires holes whose center is at 11.5mm from the board edge.
  • review choice of external LED connector type and clearance
  • if using a non-polarized connector, change pinout so that connecting the LEDs the wrong way cannot cause damage
  • add 12V fan connector and on/off circuit (with optocoupler)
  • increase sensitivity to ~20fA / LSB