Laser connections
The CTL200-1 / CTL200-2 is compatible with Type 1 / Type 2 butterfly laser diodes. Note that it is only compatible with floating diodes.
Terminal block connections
- RX, TX: Serial interface pins.
- AI1, AI2: Auxiliary analog inputs between 0 and 2.5 V.
- DO1, DO2: Digital outputs that replicate the status of LASER and TEMP LEDs on 3V3 logic levels.
- LCK: Interlock pin.
- VCC: 3V3 output supply pin. This pin is not designed to supply the CTL200.
Power supply
The CTL200 is provided with a 5.9 V / 3 A power supply. The CTL200 is supplied with 5 V or 6 V via the barrel connector. With 5 V power supply, compliance voltages are reduced by 1 V. To supply the board with 5 V supply, set the SW3 position to ON.
In the worst case, the total current required by the CTL200 is 1.4 A for the 200 mA version (1.6 A for the 400 mA version...). This corresponds to a situation where the maximum current is drawn by the laser and the TEC. TEC voltage limits (vtmin and vtmax) can be used to reduce this requirement. The total current drawn can be approximated by I = ILASER + 0.8 × ITEC + 100 mA.
Important note: The VCC pin on the terminal block is not designed to supply the CTL200.
Configuration switch
- Switch 1: When SW1 is ON, the user configuration is loaded at start-up. When SW1 is OFF, the default configuration is loaded at start up.
- Switch 2: SW2 is used for firmware update. It should be kept OFF for normal operation.
- Switch 3: SW3 is used to switch between power supplies. Set SW3 to ON when supplying the CTL200 with a 5 V power supply.
- Switch 4: Unused.
Serial interface
The serial interface can be accessed either via the micro USB connector or via the TX and RX pins of the terminal block (3V3 logic level / 5V tolerant).
The serial interface is the only way to configure the CTL200 operating parameters. Once the configuration is done, it can be saved to the internal memory with the save command. If the configuration switch SW1 is ON at start up, the CTL200 will load the user-defined configuration and the serial interface is no longer needed.
The CTL200 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
Note: If your computer does not recognize your controller, please see also this FAQ.
Example use of the serial port terminal
>>
>>version
V0.1
>>rtset
10000.000000
>>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. The GUI provides an effective mean of tuning the PID gains of the temperature controller.
Commands
| Command | Description | Type | Unit | Default | Min | Max |
|---|---|---|---|---|---|---|
| lason | Disable | enable laser current | R/W | 0 | 0 | 1 | |
| ilaser | Laser current. | R/W | mA | 0.0 | 0.0 | |
| vlaser | Laser voltage | R | V | |||
| ldelay | Time between when the controller lights up and when the laser lights up | R/W | ms | 1000.0 | 10.0 | 100000.0 |
| ilmax | Software current limit | R/W | mA | 1000.0 | 0.0 | 1000.0 |
| lckon | Disable | enable interlock functionality | R/W | 0 | 0 | 1 | |
| lmodgain | Laser current AIN1 modulation gain | R/W | mA/V | 0 | -100000.0 | +100000.0 |
| tecon | Disable | enable TEC current | R/W | 0 | 0 | 1 | |
| tprot | Disable | enable temperature protection | R/W | 1 | 0 | 1 | |
| rtset | Thermistor resistance setpoint | R/W | Ω | 10000.0 | rtmin | rtmax |
| rtact | Actual value of thermistor resistance | R | Ω | |||
| itec | TEC current | R | A | |||
| vtec | TEC voltage | R | V | |||
| pgain | Proportional gain of the temperature controller | R/W | 0.001 | 0.0 | 0.1 | |
| igain | Integral gain of the temperature controller | R/W | 0.0001 | 0.0 | 0.1 | |
| dgain | Differential gain of the temperature controller | R/W | 0.001 | 0.0 | 0.1 | |
| rtmin | Minimum thermistor resistance. If temperature protection is enabled, the laser current is automatically disabled below this value. | R/W | Ω | 5000.0 | 500.0 | 200000.0 |
| rtmax | Maximum thermistor resistance. If temperature protection is enabled, the laser current is automatically disabled above this value. | R/W | Ω | 15000.0 | 500.0 | 200000.0 |
| vtmin | Minimum TEC voltage | R/W | V | -2.0 | -3.0 | 0.0 |
| vtmax | Maximum TEC voltage | R/W | V | 2.0 | 0.0 | 3.0 |
| tmodgain | Temperature AIN2 modulation gain | R/W | Ω/V | 0 | -100000.0 | +100000.0 |
| iphd | Photodiode current | R | mA | 0.0 | 2.5 | |
| ain1 | AI1 pin voltage | R | V | 0.0 | 2.5 | |
| ain2 | AI2 pin voltage | R | V | 0.0 | 2.5 | |
| tboard | Board temperature | R | °C | |||
| version | Firmware version | R | v0.17 | |||
| status | Return lason, vlaser, itec, vtec, rtact, iphd, ain1, ain2. | R | ||||
| 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 |
Status LEDs
- STATUS: Always ON during normal operation. Blinks when an error is detected (err > 0).
- LASER: Turns ON when the photodiode current is above 10 µA.
- TEMP: Turns ON when the thermistor resistance is within 1 Ω of the setpoint.
The digital outputs DO1 and DO2 replicate the status of LASER and TEMP LEDs on a 3V3 logic level.
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: LASER_UNDERTEMPERATURE (err = 4)
- B3: LASER_OVERTEMPERATURE (err = 8)
- B4: CMD_UNKNOWN (err = 10)
- B5: CMD_INVALID_ARG (err = 20)
- B6: LASER_ON_WHILE_INTERLOCK (err = 40)
- B7: INTERLOCK_TRIGGERED (err = 80)
Modulation inputs
The CTL200 has two current modulation inputs available on SMA connectors:
DC modulation input for modulation between DC and 10 MHz. A jumper allows to choose between 3 modulation gains (Low = 250 µA/V, Medium = 2.5 mA/V or High = 25 mA/V for the B-200 version). Modulation range is between -1.3 V and 1.3 V for Low and Medium modulation gains and between -1.3 V and 1.0 V for High modulation gain. Input impedance is 50 Ω.
AC modulation input for modulation above 100 kHz. Modulation range is ±5 V (50 Ω input impedance). Modulation gain is 20 mA/V.
Thermal management
The TEC voltage limits (vtmin and vtmax) and the thermistor resistance limits (rtmin and rtmax) provide an effective way of protecting the laser against thermal runaway. For reliable operation, the aluminium cooling base plate must be properly heatsunk.
Interlock
An optional interlock functionality can be activated with the lckon 1 command. Laser current is then disabled when the LCK pin is pulled low. The figure below shows the use of the interlock with an external opto-isolator:
Once laser current has been disabled, the serial command lason 1 must be sent to re-enable the laser current.
The behavior of the interlock pin can be inverted with the command lckon 3.
Analog modulation with AIN1 and AIN2
The analog input AIN1 can be used in conjunction with the command lmodgain (in mA/V) to modulate the laser current: ilaser' = ilaser + lmodgain x (V_AIN1 - 1.25 V).
The analog input AIN2 can be used in conjunction with the command tmodgain (in Ω/V) to modulate the laser temperature: rtset' = rtset + tmodgain x (V_AIN2 - 1.25 V).
