remote interface for inductive cooking plate (Hendi 3500M)

The control knob will be used for interaction w/ the user. The pot signal will be modified by the electronic, regarding to the wish of the user (and if selected by the remote value).

You can use a simple switch/relay to enable heating (activate one of two fixed power values) Or you can use the RS232 interface for communication, and select the power value stepless.

There are 5 operation modes, you chose on the control know:

• off/standby (this cooking plate hasn't really a power off-switch - but in this state its not possible to enable heating)
• remote on/off with low power (e.g. 1000W, configurable) by external switch/relay
• remote on/off with high power (e.g. 3500W, configurable) by external switch/relay
• remote control (0W, 500W up to 3500W) by RS232 protocol
• manual mode for easy standalone operation (knob can be used across the whole range, like w/o modification)

see also:

• further description (german language)
• https://hobbybrauer.de/forum/viewtopic.php?f=58&t=1732 (german language)

• offers RS232 interface with 9600baud for external control
• on/off remote can be uses by simple external switch/relay w/o RS232 counterpart station
• galvanic isolation of electrical interface (no hazard by touching the external interface!)
• interface PCB is looped just between the 4 wire connector between display PCB and the control knob PCB
• mechanical power switch of control knob overrules every manipulation of electronic - Off state is as secure as w/o this electronic. This ensures a bug can not lead into unwanted heating.
• Analog value of control knob are passed through or modified by the firmware regarding selected operation mode.
• heating power is displayed on the common numeric display
• two LEDs indicate the operation state
• electronic is powered by the cooking plate itself

• electronic uses a simple AVR 8-bit microcontroller
• easy remote protocol uses messages
• Messagetype: Preamble, length of Payload, Payload, checksum (simple xor), delimiter
• needs periodic messages (~2.5 sec) to ensure save state if electrical connection is lost

Everything you do, you do at your own risk. Keep all safety rules in mind! Be aware of electrical shock or other hazards!