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THORLABS LDC 500, Instruction Manual

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THORLABS LDC 500 Instruction Manual Download Page 11

Doc 2136-D01 Rev E 1/24/02

 

2-4  

2-4

The current limit can also be adjusted with the output switched on. In any case, you should avoid an adjustment when 
the LED "LIM" (7) lights up.  
 
 
 
 

2.3.2   

Selecting the laser diode polarity 

With the LDC 500, all possible polarities of the laser diode and the monitor diode can be driven. The laser diode will 
always be driven with respect to ground. Compared with a floating driver stage, this operating mode has the 
advantages of higher security for the laser diode, better stability, and lower noise of the laser current by allowing the 
case of the laser diode to be grounded. 
 
Prior to switching on the laser current, the correct polarity of the laser diode must be selected. 

 

Procedure to select the laser polarity: 
 

•

 

Switch off the LDC 500. 

•

 

Select the designed polarity with the switch "LD POL" (6). 

 
When operating laser diodes with a built-in monitor diode, the common pin of the laser diode and the photodiode is 
the ground pin. 
 
The selected polarity of the output is indicated with the LED "LDA" (1) or "LDC" (2) LED to the left of the 4-1/2 
digit display . 
 
For safety reasons, there is a middle position of the switch "LD POL" (6) in which the laser is disabled. 

Note: 

If the middle position of the switch "LD POL" (6) is selected, neither the LED (1) nor (2) lights up. The laser 
current cannot be switched on. 

If the laser diode is connected correctly (refer to chapter 2.3.3), but the polarity of the laser diode selected incorrectly 
via switch (6), the laser diode current cannot be switched on. 
 
If the position of the switch "LD POL" (6) is changed with the laser current switched on, the laser diode current is 
switched off automatically. 

Note: 

For safety reasons you should select the polarity for the laser diode only with the laser diode current output 
switched off. 

2.3.3   

Connecting laser diode and photodiode 

The LDC 500 can drive

 

all laser diodes up to a maximum current range of 0.5A. 

 
If laser mounts by 

Thorlabs

 are used, the input "LD INTF" of the laser mount is to be connected to the DB9 female 

jack labeled "LD OUTPUT" (5) with the cable LDC500-CAB.  
 
 

Summary of Contents for LDC 500

Page 1: ...LDC 500 Laser Diode Controller Instruction Manual Doc Number 2136 D01 Rev D 7 9 2000 Copyright 1997 Thorlabs Inc 435 Route 206N Newton NJ 07860 USA Phone 973 579 7227 FAX 973 300 3600 www thorlabs com ...

Page 2: ...the current limit ILIM 2 3 2 3 2 Selecting the laser diode polarity 2 4 2 3 3 Connecting laser diode and photodiode 2 4 2 3 4 Constant current mode CONST I 2 6 2 3 5 Constant power mode CONST P 2 7 2 3 6 Calibrating the optical power display 2 9 2 3 7 Analog modulation of the laser diode 2 9 2 3 8 Control Output Laser Current Monitor 2 10 3 Remote control 3 1 4 Service 4 1 4 1 Changing the line vo...

Page 3: ...he laser diode works as a stable optical transmitter The LDC 500 laser diode controller is well suited for Safe and simple operation of all laser diodes up to 0 5A Power stabilized light sources Wavelength tuning by controlling the current Wavelength modulation by current modulation To protect the laser diode against damage the LDC 500 provides the following protection circuitry Softstart function...

Page 4: ... the laser diode can be modulated via a modulation input at the rear of the unit If an error occurs or the limit for the laser current is reached the corresponding LED lights up and a beeper sounds a short warning signal The installed line filter and the transformer shielding provide low ripple output An internal fan provides cooling of the LDC 500 to protect the unit against overheating and high ...

Page 5: ...ower 1 µW 10 µW jumper Setting accuracy 2 µA Drift 1 µA Current limit Setting accuracy 1 5 mA Resolution 0 1 mA Analog Modulation Control Input Output Input impedance 10 kΩ Bandwidth current control DC 150 kHz Laser current modulation coefficient 50 mA V Control Output Laser Current Monitor 0 to 10V 50mA V Connectors Laser diode photodiode LD ON signal interlock DB9 Female Modulation input BNC Con...

Page 6: ... unit is grounded via the ground conductor To avoid electric shock hazard the plug of the line cord must be connected to a correctly grounded power outlet Grounding of the unit by the ground conductor of the line cord is necessary for safe operation An interrupt of the ground conductor may cause extreme danger and injuries to persons by electric shock To ensure safe operation of the unit always ke...

Page 7: ...horlabs does not warranty that the unit will work without errors and interruptions or that this manual is free of errors Thorlabs is not liable for consequential damages Limitation of warranty This warranty shall not apply to defects resulting from inadequate treatment interfacing modification misuse operation outside the environmental specifications or unauthorized maintenance No other warranty i...

Page 8: ...Indicates no laser diode connected 7 LED LIMIT Adjusted current limit reached 8 LED ENABLE Laser current is switched on 9 ENABLE Button Enables the laser current on or off 10 Knob for adjusting the set value 11 Line switch 12 LIM I Potentiometer for setting the current limit 13 CAL Potentiometer for calibrating the power display 14 LED PLD Displaying the optical output power 15 LED IPD Displaying ...

Page 9: ... setting the photodiode current range Fig 2 2 Operating elements on the rear panel 1 Modulation input analog control input MOD IN 2 Control Out Laser Current Monitor 3 Ventilation Fan 4 Connector for chassis ground 5 Connector LD OUT for laser diode photodiode interlock status LED DB9F 6 Switch LD POL for selecting the laser diode polarity 7 Serial number of the unit 8 Letterplate displaying the a...

Page 10: ...cy is reached however after a warming up time of approximately 10 minutes 2 3 Operating the LDC 500 2 3 1 Setting the current limit ILIM Before operating a laser diode always set the current limit to the maximum desired operating current for your laser Refer to the laser manufacturer s data to determine the safe operating current for the laser NOTE Many laser manufacturers supply generic data shee...

Page 11: ...todiode is the ground pin The selected polarity of the output is indicated with the LED LDA 1 or LDC 2 LED to the left of the 4 1 2 digit display For safety reasons there is a middle position of the switch LD POL 6 in which the laser is disabled Note If the middle position of the switch LD POL 6 is selected neither the LED 1 nor 2 lights up The laser current cannot be switched on If the laser diod...

Page 12: ...TPUT jack 5 are contacts to allow for an optional externally connected Interlock switch Open contacts on this switch will prevent the unit from operating or shut the unit down if it is already operating The unit can only be Enabled if the switch contacts are closed If no interlock switch is used this feature can be bypassed by connecting Pin 1 to Pin 5 with a wire as shown in Fig 2 4 Connecting th...

Page 13: ...ve terminal of the battery to pin 4 Note A wrong polarity of the battery may destroy the photodiode 2 3 4 Constant current mode CONST I Procedure to operate in constant current mode Switch on the LDC 500 refer to chapter 2 2 Select a suitable current limit ILIM refer to chapter 2 3 1 Select the appropriate laser polarity refer to chapter 2 3 2 Connect the laser diode refer to chapter 2 3 3 Select ...

Page 14: ...diode current is switched off automatically LED ENABLE 8 turns off LED OPEN CKT 6 lights up and a beeper sounds a short warning signal If the output is switched on while the interlock is closed and there is no laser diode connected at first the LED ENABLE 8 lights up and the output is switched on Immediately afterwards the LDC 500 recognizes the absence of the laser diode switches the output off t...

Page 15: ...LD increases to the set current limit ILIM If the laser current ILD is limited by the selected current limit ILIM ripple and noise no longer correspond to the specifications for normal operation refer to chapter 2 3 1 However the set maximum current ILIM cannot be exceeded If the connection to the laser diode is interrupted during operation the output is switched off automatically LED ENABLE 8 tur...

Page 16: ...ode CONST I With the adjustment knob 10 either set a laser current ILD or a monitor current IPD where the optical output power of the laser diode is known e g from the data sheet of the laser diode Alternatively the laser power can also be measured with an optical power meter Select the display PLD 5 with button 18 or 19 Calibrate the display PLD with potentiometer CAL PD 13 to the value of the ac...

Page 17: ...d to the value of the current limit ILIM If the laser current ILD is limited by the selected current limit ILIM ripple and noise no longer correspond to the specifications for normal operation refer to chapter 2 3 1 However the set maximum current ILIM cannot be exceeded 2 3 8 Control Output Laser Current Monitor A rear panle BNC labelled CTL OUT allows the laser current to be monitored with a vol...

Page 18: ...nterlock If a relay contact or an open collector transistor is switched in the interlock line refer to chapter 2 3 3 the output can be switched off automatically at any time However an automatic reactivation is not possible Setting a set value If the adjust knob 10 is set to the CCW stop the set value can be controlled with an analog voltage of 0 10 V thus a setting via a D A converter card is eas...

Page 19: ...over back onto the unit and fasten it with the 2 screws If necessary change the main fuse refer to chapter 4 2 4 2 Replacing the main fuse If the main fuse has blown due to line distortion incorrect line voltage or other causes it can be easily replaced from the rear without opening the unit Attention To avoid fire risk only the fuse designated for the line voltage must be used The recommended fus...

Page 20: ...ar the front of the PCB Install a shorting jumper across JP6 to set the display range to 0 200mW Remove any shorting jumper across JP6 to set the range to 0 20mW Replace the cover and secure with the 2 mounting screws 4 4 Maintenance and repair The LDC 500 does not need regular maintenance by the user The unit and the LCD display can be cleaned with a soft moist cloth and a mild detergent The LDC ...

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