TEC100L User Guide

Quickstart

1. Make sure the TEC100L is in default jumper configuration as shown in grey in the image below:
   

   

   • J1: 2-3
   • J2: 2-3
   • J3: 2-3
   • J4: 2-3
   • J5: 1-2
   • J6: OFF

2. Connect the thermistor between TH+ and TH- pins.

3. Connect the Peltier element between TEC+ and TEC- pins.

4. Supply the board with 5 V between the VCC and GND pins.

5. The thermistance is measured with a Wheatstone bridge followed by an instrumentation amplifier. Measure the voltage V_TACT at the amplifier output (TACT pin). The thermistor value R_th is given by the formula:

   R_th = 10 kΩ * (4.096 V - (V_TACT - 1.65 V)) / (4.096 V + (V_TACT - 1.65 V))

   

6. The analog PID control loop tries to make the voltage V_TACT equal to the setpoint V_TSET. Monitor the TSET pin and adjust the setpoint with the R16 potentiometer to obtain the desired value of V_TSET. For a standard 10 kΩ thermistor at 25 °C, adjust V_TSET to 1.65 V.

7. Monitor the voltages V_ITEC and V_VTEC at the ITEC and VTEC pins. The current I flowing between the pins TEC+ and TEC- is given by the formula:

   I = 0.5 A/V * (V_ITEC - 2.5 V)

   The voltage V = V_TEC+ - V_TEC- is given by:

   V = 2 * (V_VTEC - 2.5 V)

   For the TEC100L with serial number lower than 6200, the formula for the TEC current is I = 1.0 A/V * (V_ITEC - 2.5 V). For the TEC100L with serial number lower than 1600, the formula is V = V_VTEC - 2.5 V.

8. Enable the current output stage by setting the jumper J6 on the ON position. The current output stage is current limited to 1.15 A. The LED D2 turns ON when the system reaches the current limit.

Control the setpoint from an external voltage

When the jumper J1 is in position 2-3, V_TSET is adjusted with the SETPOINT potentiometer and can be monitored on the TSET pin. When J1 is in position 1-2, the voltage V_TSET can be controlled externally at the TSET pin.

Adjusting the PID gains

The PID controller gains are adjusted to work out-of-the-box with a typical laser in butterfly package. If the preset gains do not work for your laser, you can set the jumpers J3 and J4 in position 1-2 and ajust the gains with the GAIN1 and GAIN2 trimmer. The integrator gain is inversely proportional to GAIN1. The proportional gain is proportional to GAIN2/GAIN1.

Below is a proposed procedure to adjust the gains:

1. Turn off the board.

2. Set the jumpers J3 and J4 in position 1-2 for manual gain adjustment.

3.Set the gains to a minimal value by turning GAIN1 trimmer counterclockwise and GAIN2 trimmer clockwise.

1. Set J1 in position 1-2. Apply a square wave on TSET with a 10-second period and an amplitude of 0.3 V peak-peak around 2 V. If needed, use a longer period to give the system enough time to respond.

2. Monitor TACT on an oscilloscope.

3. Turn on the board. You should observe something similar to the figure below (TSET: blue, TACT: yellow).

   

4. Increase GAIN1 until TSET oscillates:

   

   and then slowly lower GAIN1 to get damped oscillations:

   

5. Increase GAIN2 to optimize the settling time:

   

Drive the output amplifier from an external voltage

In the standard jumper configuration (J5 on position 1-2), the output amplifier creates a voltage V between the pins TEC+ and TEC- from the output V_VDRV of the PID control loop:

V = 5.05 V - 3.05 V_VDRV.

You can bypass the PID control loop and control directly the output amplifier from the VDRV pin by setting the jumper J5 on position 2-3.