Emulator to replace Intersil CA3162/CA3162E using Arduino on bare ATmega

This Arduino sketch emulates Intersil CA3162/CA3162E (also NTE2054, ECG2054) in Solomon SL-30 soldering station. It's written to run on bare ATmega8 or ATmega328 MCU, but can be easily ported to other Arduinos/MCUs.

Differences from CA2162E:

• Emulator don't have differential input, accepts only positive voltage, i.e. works only in configurations where CA3162E pin 10 is connected to ground.
• Zero/gain ajust done in software.
• No hold mode, no fast mode.
• ADC resolution depends on the reference voltage used. In case of ATmega8 internal AREF it will be 3mV (or ~3 degrees of Celsius for SL-30).

Emulator requires minimum external components:

• Decoupling ATmega VCC and AREF pins to GND via 0.1uF ceramic caps is required.
• Interfacing with transistor based digit drivers needs ~ 1K resistors in transistor base lines.
• It's recommended to connect RESET pin to VCC via 10K resistor.

Calibration

To calibrate the emulator by voltage:

• Connect Arduino pin 9 (PB1 of ATmega, pin 15 on DIP28) to ground. This will force uncalibrated ADC value to be output on the display;

• Connect your voltmeter to Arduino A0 pin (PC0 pin of ATmega, pin 23 on DIP28);

• Write down pair of values: value on the display, millivolt value on the voltmeter;

• Repeat previous step 2-3 times, at different input values. For example You will get the following table:

  Display	Voltmeter, mV
  83	100
  184	203
  307	329
  589	620

• Find linear approximation for this data. For eample on http://www.wolframalpha.com/ enter the data like this: linear fit {83, 100}, {184, 203}, {307, 329}, {589, 620}. You will get an expression like this: 1.02812 x + 14.0734

• Use the multiplier from that expression as calib_mul and the addend as calib_add in the sketch.

To calibrate Solomon SL-30 by temperature use the same technique, but use measured temperature instead of voltage.

Relevant information

• CA3162 datasheet
• CA3161 datasheet
• Solomon soldering stations schematics and repair manual, tuning manual - in Russian
• Using ATmega8 with internal 8MHz oscillator as minimal Arduino tutorial and another one.