Supply connector
- V+: Power supply input (9 V to 33 V).
- V-: Power supply return.
Communication connector
- ALM: Alarm output (3V3 logic, see Alarm).
- INT: Interlock pin (see Interlock).
- TX: UART TX pin.
- RX: UART RX pin.
Analog connector
- AIN: Analog input with a voltage range between 0 and 2.5 V. The voltage at the pin AIN can be retrieved with the ain command.
- TH+ / TH- Thermistor pins.
- H+ / H-: Heater connections.
Configuration switch
- 1: CFG If CFG is ON at start-up, the board will start with the user-defined configuration. Otherwise, the default configuration is loaded.
- 2: BM This pin is used for firmware update. Set to OFF for normal operation.
Serial interface
The serial interface can be accessed via TX and RX pins on the communication connector (3V3 logic level / 5V tolerant). The serial interface is the only way to configure the HTC200 operating parameters. Once the configuration is done, it can be saved to the internal memory with the save command. If the CFG input is ON at start-up, the HTC200 will load the user-defined configuration and the serial interface is no longer needed.
The HTC200 can be controlled directly from a serial port terminal (e.g. Teraterm on Windows) with the following configuration:
- Baud rate: 115200
- Parity: None
- Bits: 8
- Stopbits: 1
- Flow control: None
Example use of the serial port terminal
>>version
V0.1
>>rtset
10000.000000
>>tecon 1
1
>>rtact
10000.023438
>>rtset 12000
12000.000000
>>rtact
11999.853516
Note: Each command must be followed by \r\n.
Graphical User Interface
A Graphical User Interface installer can be downloaded at this link.
Control commands
| Command | Description | Type | Unit | Default | Min | Max |
|---|---|---|---|---|---|---|
| Settings | ||||||
| tecon | Disable | enable TEC/Heater current | R/W | 0 | 0 | 1 | |
| rtset | Thermistor resistance setpoint | R/W | Ω | 10000.0 | rtmin | rtmax |
| tset | Temperature setpoint | R/W | °C | 25.0 | tmin | tmax |
| Gains | ||||||
| kprop | Proportional gain | R/W | A/°C | 0.27 | 0.0 | 100.0 |
| tint | Integral time | R/W | s | 1.21 | 0.0 | 10000.0 |
| tder | Differential time | R/W | s | 0.0 | 0.0 | 1000.0 |
| sign | Feedback sign | R/W | +1.0 | -1.0 | +1.0 | |
| Limits | ||||||
| tvlim | TEC/Heater voltage limit | R/W | V | 20.2 | 0 | 20.2 |
| itmin | Minimum TEC/Heater current | R/W | A | 0 | 0 | 4.1 |
| itmax | Maximum TEC/Heater current | R/W | A | 4.1 | 0 | 4.1 |
| rtmin | Minimum thermistor resistance. If almode set to TPROT, ALM is raised below this value. | R/W | Ω | 1000.0 | 500.0 | 200000.0 |
| rtmax | Maximum thermistor resistance. If almode set to TPROT, ALM is raised above this value. | R/W | Ω | 15000.0 | 500.0 | 1000000.0 |
| rttol | Temperature stable thermistor tolerance. If almode set to TSTABLE, ALM is raised when |rtact - rtset| < rttol. | R/W | Ω | 1 | 0 | 50000 |
| Monitoring | ||||||
| rtact | Actual value of thermistor resistance | R | Ω | |||
| tact | Actual value of temperature | R | °C | |||
| itmon | Monitored TEC/Heater current | R | A | |||
| itec | Set TEC/Heater current | R | A | |||
| vtec | Monitored TEC/Heater voltage | R | V | |||
| rtec | TEC/Heater resistance | R | Ω | |||
| tboard | Board temperature | R | °C | |||
| tjunc | TEC/Heater driver junction temperature | R | °C | |||
| vbus | Input supply voltage | R | V | |||
| ibus | Input supply current | R | A | |||
| ain | Analog input voltage | R | V | |||
| Misc | ||||||
| almode | Set the ALM mode | R/W | 0 | 0 | 2 | |
| intmode | Set the INT pin mode | R/W | 0 | 0 | 2 | |
| version | Firmware version | R | v0.1 | |||
| save | Save configuration in internal memory (no argument) | W | ||||
| model | Return the board model | R | ||||
| serial | Return the serial number | R | ||||
| userdata write | Write the user data (e.g. userdata write ABC) | W | 31 chars | |||
| userdata | Read the user data | R | ||||
| brate | UART baud rate | R/W | baud | 115200 | 9600 | 460800 |
| err | Return the error code in hexadecimal format (no argument) | R | ||||
| errclr | Clear the error code (no argument) | W | ||||
Error codes
The command err returns a 32-bit number in hexadecimal representation which concatenates the detected errors (B0 is the Least Significant Bit):
- B0: UART_BUFFER_OVERFLOW (err = 1)
- B1: UART_CMD_BEFORE_PROMPT (err = 2)
- B2: RESERVED (err = 4)
- B3: RESERVED (err = 8)
- B4: BUS_UNDERVOLTAGE (err = 10)
- B5: BUS_OVERVOLTAGE (err = 20)
- B6: BUS_OVERCURRENT (err = 40)
- B7: BUS_OVERPOWER (err = 80)
- B8: BOARD_OVERTEMPERATURE (err = 100)
- B9: LOAD_UNDERTEMPERATURE (err = 200)
- B10: LOAD_OVERTEMPERATURE (err = 400)
- B11: CMD_UNKNOWN (err = 800)
- B12: CMD_INVALID_ARG (err = 1000)
- B13: FET_OVERTEMPERATURE (err = 2000)
- B14: BOARD_MODEL_UNKNOWN (err = 4000)
- B15: TVLIM_LOWERED (err = 8000)
Interlock
An optional interlock functionality can be activated with the intmode 1 command. Heater control is enabled when the INT pin is high, else it is disabled. The behavior of the interlock pin can be inverted with the command intmode 2.
Alarm
The ALM output behavior can be set by the almode commmand:
- 0 (default): ALM is high when an error occured.
- 1: Temperature stable indicator. ALM is high when actual temperature is within the setpoint for the defined tolerance (that is when |rtact - rtset| < rttol).
- 2: Temperature protection. ALM is raised when actual temperature tact is outside the defined limits (tmin and tmax). Using this mode the ALM pin can be connected to the interrupt of a current driver to protect the driven device.
Heater voltage limit
The maximum is set by the tvlim commmand.
The default hvlim value is set to 20.2 V and is designed to operate from a nominal 24 V supply.
If the input supply voltage, as given by the vbus commmand, is lower than hvlim + 1 V, then the maximum heater voltage is internally limited to vbus - 1 V and a HVLIM_LOWERED error is raised.
Current source
The HTC200 can also be operated as a standalone current source. You can use for instance the following commands to set the output current to 2 A:
>>tecon 0
0
>>curron 1
1
>>itec 2.0
2.00000
Thermal management
For reliable operation, the baseplate must be properly heatsunk.
If tboard exceeds 85 °C, the controller keeps operating and a BOARD_OVERTEMPERATURE warning is raised.
This flag indicates an excessive ambient temperature or improper heatsinking.
If tjunc exceeds 120 °C, the temperature control shuts down and a FET_OVERTEMPERATURE error is raised.
For reliable operation, tjunc should not exceed 105 °C for extended periods.
