Model No. SLICE-DCC

Document Revision: 1

Document Last Updated on 2019/08/29 10:19

Please read Limited Warranty and General Warnings and Cautions prior to operating the SLICE-DCC.

Click here for the main manuals page.
Click here for the SLICE-DCC Quick Start Guide.
Click here for the SLICE-DCC API.
Click here for the SLICE-DCC web page.
Click here for the Github page for SLICE-DCC GUI
Click here for the Github page for SLICE-DCC firmware revisions
Please check back for added functionality. Contact sales [at] vescent [dot] com for questions and corrections, or to request added functionality.

	Warning. Pay special attention to procedures and notes. If procedure is not followed carefully, damage to the SLICE-DCC or devices connected to it may occur.
	Potential for electrical shock hazard.

The SLICE-DCC Current Controller is intended for driving laser diodes. When using lasers particular care must be given to exposure hazards.

The SLICE-DCC is a low-noise, economical current controller (see figure 1). It serves as a low-noise current source providing up to 2 A. It is configured to work with a grounded cathode in either a constant current or a constant power mode.

Fig. 1: The SLICE-DCC

• SLICE-DCC dual-channel Current Controller
• AC power cord with appropriate wall plug for you location (if known)
• Two 6 ft SMA cables
• Two D2-007 Breakout boards
• One 50 Ω terminator for rear-panel safety interlock
• Two keys for lock out
• Final Test Documentation

Note: All modules designed to be operated in a laboratory environment.

The SLICE-DCC will accept input line voltages within the ranges shown in table 3.

An image of the front panel is shown in figure 2. The functions and connections are as follows:

1. Parameter input adjustment knobs
2. Control signal inputs
3. Signal monitor outputs
4. CH status (Constant Current or Constant Power)
5. Current enable (CH1 is ON, CH 2 is off)
6. Current or Power (not shown) set point
7. Optical Power or Diode Voltage display

Fig. 2: Front of SLICE-DCC

An image of the rear panel is shown in figure 3. The functions and connections are as follows:

1. Main On/Off power switch
2. AC line power in⁷⁾
   1. User-serviceable fuse (T 2.0 A L 250V)
3. Output trigger (BNC)
4. Input trigger (BNC)
5. USB port (Type B)
6. Interlock key receptacle
7. Door interlock
8. CH 2 Current output
9. CH 2 Modulation input
10. CH 2 Photodiode input

Fig. 3: View of rear of SLICE-DCC

The touch screen interface and the Host GUI operate in a substantially similar way, except touch is substituted for a click in the touch screen interface.

When presented with a given view, it is possible to select the functionality or edit the values in a field bordered in blue. When a particular field is actively being edited, its border will change to yellow. The Home Screen of the SLICE-DCC is shown in figure 4 and is reached by clicking the home button (figure 5) in the upper left corner of the touch screen. From the Home screen, summary control over the two channels is possible, including setting I_set or P_set,From the Home screen, you can edit the the control parameters for each channel.

In general, the status displayed in an editable field is the current status (not the result of touching the button). Touch the field to select a new value/status. For instance, in figure 4 both channels are in stand by. Touching the OFF button will initiate current delivery to the given channel.
Fig. 4: Home screen of SLICE-DCC

On the left edge of the screen is the Control Bar. At any given time, these buttons will have the following effect.

Fig. 5: Home button Returns to Home screen (figure ##).

Fig. 6: Back button Returns to previous screen. Changes will be lost if not accepted before using the Back button.

Fig. 7: Lock button (shown in unlocked mode) Locks out further modification of parameters. Touch to lock or unlock parameter entry. When in lock mode, it is still possible to toggle the current on and off, but it will not be possible to change the set point or other operation parameters.

Fig. 8: I/O button Enters the screen for programming the front-panel I/O.

Fig. 9: System settings button Enters screen for system control settings (brightness, volume, etc.).

In most instances, there are two methods for entering parameter values: the physical rotary knobs on the front panel and the pop-up keypad on the touch screen. When using the knobs to change the value of a parameter, changes take effect immediately. When using the keypad, changes do not take effect until the enter key is touched.

If you touch an editable field for a brief moment, the border of the field will change from blue to yellow and a cursor will appear under one of the digits of the parameter value (figure 10). By turning the right knob, it is possible to increase (cw) or decrease (ccw) the value of the underlined digit. Turning the left knob will change which digit is editable (cw to move to the right and ccw to move to the left). Changes made with the rotary knobs take effect immediately.

Fig. 10: Knob adjustment of Current set point for CH 1

If you touch and hold an editable field such as the current set point, a numeric keypad will appear as seen in figure 11. You can enter in the full value of the desired parameter with this keypad. Changes entered through the keypad are not enacted until the Enter key is touched.

Fig. 11: Pop-up Keypad

The action initiated by each button of the keypad is described below.

Fig. 12: Escape button Exits keypad without accepting changes.

Fig. 13: Clear button Clears value in field being edited.

Fig. 14: Delete button Deletes last character entered.

Fig. 15: Enter button Accepts parameter edits and exits keypad.

The Home screen displays the status of both channels (figure 4). The data for each channel is arranged vertically. At a glance, for each channel, I_set, and Compliance Voltage can be read. Touching the blue window labelled Voltage [V] will cause this window to toggle from displaying Compliance Voltage to displaying dissipated Power.

The SLICE-DCC has two operation modes: Constant Current and Constant Power. The operation mode, as with most other operating parameters can be set independently for each channel. To toggle between Constant Current and Constant Power modes, from the Home screen, touch the window labelled either CH X Constant Current or CH X Constant Power. If the channel is in Constant Current Mode, you will be presented with the window seen in figure 18.
Fig. 18: Setting Maximum Current

If the channel is in Constant Power mode, you will be presented with the window seen in figure 19.

Fig. 19: Selecting Constant Power mode parameters

Touching the Window labeled Control Mode will allow you to toggle the channel back & forth between Constant Current and Constant Power modes as seen in figure 20.

Fig. 20

The user can set a maximum deliverable current so as not to exceed the rated maximum for their device. From the Home screen, touch the window labelled either CH X Constant Current or CH X Constant Power. Depending on the operation mode, you will be presented with either figure 18 or figure 19. Touch the Current Limit window and enter the maximum allowed current (in mA) as in figure 21.
Fig. 21: Set Current Maximum

In Constant Current mode a linear regulator minimizes current noise & fluctuations.

To set the current set point from the home screen, touch the Set point window for the desired channel. A long touch will cause a keypad to appear (figure 22). Enter desired value and touch the accept button.

A short touch will highlight the Setpoint window in yellow (figure 10). Use rotary knobs to select digit to edit (left knob) and value for digit (right knob).
Fig. 22: Keypad adjustment of Current set point for CH 1

To set the power set point in Constant Power Mode from the home screen, touch the window labelled Setpoint [mW] and enter the target power level (figure 23). If the window is labelled Set Point [mA], the device is in Constant Current mode and must first be switched to Constant Power mode.

It is possible to adjust the Power Setpoint when the system is either ON or in Standby mode.

Fig. 23: Setting the power set point in Constant Power mode

When the blue window labeled Enable reads OFF, the system is in standby mode and no current is delivered. Briefly touching this window will, after a 5 s pause during which a warning light will flash, cause current to begin to flow and the window will read ON.

On the rear panel of the SLICE-DCC is an input for servoing or modulating the current output. (figure 3, item 9). The transfer function for this input is 1 mA/V and the input range is ±10 V. Therefore the current can be modulated by ±10 mA. The 3-dB bandwidth of this modulation input is DC to 1 MHz.

	Although there is protection circuitry to avoid reverse biasing the diode, it is not advisable to modulate under conditions where the current would be driven in reverse polarity.
	Make sure that the modulation input cannot drive the current above the maximum rated current for your device by setting the Current Limit appropriately.

In Constant Power mode, the SLICE-DCC accepts a current input signal from the output of a photodiode (often internally mounted with the diode laser). This signal is conditioned by a trans-impedance amplifier and used as an error signal. It is further processed by a loop filter to provide a correction signal to the current to maintain constant power.

Warning. Make sure the Current Limit is set below the recommended maximum current for your laser diode and that the monitor photodiode is working and delivering a signal to the SLICE-DCC before engaging Constant Power mode. If a signal proportional to the laser power from the monitor diode is not delivered to the SLICE-DCC, the current may ramp to its maximum allowed value when Constant Power mode is engaged.

1. Connect the output of the monitor photodiode to the CH X Photodiode Input connector (labelled “10” in the back-panel image) on the back of the SLICE-DCC.
   
   In order for Constant Power mode to operate correctly, the user must set three control parameters: the responsivity of the monitor photodiode, the gain of the loop filter, and the polarity of the photodiode response. Before setting these control parameters. first set the SLICE-DCC in Constant Power mode and set the Power Setpoint. From the home screen, enter the CH X Settings screen by tapping the window labelled CH X: Constant Power. Enter values for Detector Response, Gain, and monitor photodiode Polarity.
   
   
2. Enter the value of the detector response supplied in the documentation that came with your monitor photodiode. (figure 24) Fig. 24: Setting the detector response for Constant Power mode
3. Turn the Gain all the way to 0 (zero). Turn the system ON to deliver current to the diode. Slowly turn up the Gain until the power begins to oscillate (figure 25). (Hint; It is easiest to adjust the gain for this step via the knobs as opposed to through the keypad.) Turn down the Gain until oscillation stops. Fig. 25: Setting the Gain for Constant Power
4. If more Gain moves the power away from the set point, switch the polarity from Positive to Negative (or vice versa).

The SLICE-DCC has two programmable inputs (labelled A & B) and two programmable outputs (labelled 1 and 3) on the front panel. It also has a rear panel trigger input and trigger output. Touching the I/O window on the control bar will open a screen similar to that seen in figure 26, From here, it is possible to assign control information input to the two inputs and system performance data to the two outputs,

Fig. 26: I/O programming window

These front-panel inputs and outputs are mainly intended for monitoring the performance of the SLICE-DCC and as such have slower, noisier components than the rear-panel connections.

From figure 26, if one touches either the A or B input window, the choices for input for that channel are presented (figure 27).

Fig. 27: Input choice for front-panel input

At present (Aug, 2019), the only input option is a modulation signal. The SLICE-DCC can respond to a modulation or control signal over a bandwidth of DC to 1 MHz.

From figure 26, if one touches either the 1 or 2 output window, the choices for output for that channel are presented (figure 28).

Fig. 28: Output choices for front-panel input

One can choose to monitor the current output and/or the optical power as measured at the photodiode input.

External control of the SLICE-DCC is accomplished via a TTL trigger.⁸⁾ 0 to 0.8 V TTL is low and 2 to V_CC is TTL high.

The Trigger Out on the back panel of the SLICE-DCC can be programmed to go high if an interlock (key or door) is opened. The screen shown in figure 29 will be reached by touching I/O > Trigger Out. Checking either box will cause the Trigger Out to go high if either the door interlock or the key interlock is opened. Fig. 29: Setting an output trigger

The input trigger can be used to turn on or off the current for either or both channels. From any screen, touch I/O > Trigger In. You will be presented with the window in figure 30. Select which channels you wish to control with the incoming trigger. In figure 31, current to CH 2 will be disabled if the Trigger In goes high.

Fig. 30: Programming the rear-panel trigger in

Fig. 31: CH 2 is controlled by input trigger

Touching the System Settings button on the Control Bar (figure 9) will open the System Settings screen as seen in figure 32. Fig. 32: User-programmable system settings

From this screen, adjustments to the brightness of the screen and the volume of the audio feedback can be made.

Change the input impedance of the two front-panel input ports. Select either 50 Ω or 1 MΩ.

Current firmware versions are reported here.

From time to time, Vescent will upgrade the firmware for controlling the SLICE-DCC. The procedure to upgrade the firmware is given here.

If accessed through a PC Host GUI, the Settings screen (figure 33) also has the ability to assign the COM port for the device. If viewed through the GUI, there are no brightness or volume controls as these should be set on the PC directly. Fig. 33: User-programmable system settings from host GUI

If either the key switch is deactivated or the interlock is opened while the system is operating, the SLICE-DCC will stop delivering current and the Enable window will flash red with INTERLOCK displayed (figure 34). In order to resume normal operation, interlocks must be restored to their operational state and the window must be touched to reset the tripped interlock.
Fig. 34: Interlock Open state

If the SLICE-DCC attempts to deliver current, but is unable to do so, it assumes an open circuit fault. The Enable window on the Home screen for that channel will flash red with the warning “Open Circuit/Over Voltage” (figure 35).

Fig. 35: Open Circuit detected

It is possible to control the SLICE-DCC from a Windows^®-based PC using the GUI written for this purpose. In order to use the GUI, you must first download the latest version, connect the PC to the SLICE-DCC, and assign a COM port to the SLICE-DCC. The following describes the steps involved.

1. Download and store the latest GUI executable from the Vescent FTP site (or request copy of executable GUI from sales [at] vescent [dot] com).
2. Connect the SLICE-DCC to the PC using a USB type B cable.
3. Turn on the SLICE-DCC.
4. On the PC, double click on the SLICE-DCC GUI to start the GUI.
5. On your PC, go to Start > Control Panel > Device Manager > Ports
   1. Identify which COM Port is labeled “STMicroelectronics Virtual COM Port (COMXX)” or similar. Note the value of XX.
6. On the SLICE-DCC GUI, click on the Settings icon to get to the window shown in figure 36. Fig. 36: Settings screen when viewed by GUI
7. Click on the OFF button below COM Port. You should see a menu similar to the one shown figure 37. NOTE: The COM port numbers may differ from those shown below. Fig. 37: COM port selection
8. Select the COM port identified in the step above (usually the last COM port in the list; COM11 in this example). The window in figure 38 should appear if the connection is successful. Fig. 38: Ready to upgrade

The GUI should now actively control the SLICE-DCC. You should only have to do the above steps once from a given PC. After assigning the COM port, the system will recognize the device in the future (unless you reassign the COM port to another device).

From time to time, Vescent will upgrade the firmware for controlling the SLICE-DCC. The procedure to upgrade the firmware is given here.

It is possible to control the SLICE-DCC through serial commands. Click here to access the SLICE-DCC API.

Please contact sales [at] vescent [dot] com for information.

There are no user-serviceable parts inside this instrument. Refer all repairs to the manufacturer. Work performed by persons not authorized by Vescent Photonics may void the warranty.