ionpak-thermostat/hardware/errata.md

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)
• Meanwell DC/DC is coupling noise into pA input
• 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