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Specialists in Fluoresence Microscopy - DESIGN TO INTEGRATION

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Dual Opto

LED

Instruction Manual

Summary of Contents for Dual OptoLED

Page 1: ... co uk Free Phone 08453301267 UK only Tel 44 0 1795590140 Fax 44 0 1795594510 Specialists in Fluoresence Microscopy DESIGN TO INTEGRATION e Microscopy DESIGN TO INTEGRATION PRE1 PRE2 PRE3 Dual OptoLED Instruction Manual ...

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Page 3: ...escence This is especially important with ULTRAVIOLET LEDs which will not appear bright to the human eye but can cause permanent damage if not used with care 2 Our standard LED heads have built in protection to avoid damage however if in any doubt then please check with Cairn as to the rated power of the supplied heads and use accordingly 3 The OptoLED is typically supplied in conjunction with our...

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Page 5: ...n 1 2 Installation Guide 2 2 1 Front Panel 2 2 2 Rear Panel 4 3 Technical Summary 7 4 General Operating Notes 10 5 Specifications 14 6 Technical support 15 7 Appendix 16 7 1 LED Head Connections 16 7 2 Overload Protection 17 ...

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Page 7: ...levels for that type of LED In addition digital inputs are provided to switch each LED on and off independently with rise and fall times of less than 100 nanoseconds The OptoLED can be configured so that a single control signal can be used to switch between the two LEDs according to its logic level Each channel has a meter which can be switched to display either current in amps or power in watts B...

Page 8: ... on the rear of the unit 2 1 Front Panel OFF GATE ON Switch This switch allows the digital control signals to be overridden These signals are applied via the GATE input on the rear panel but in the OFF position the LED is always off and in the ON position the LED is on so long as a non zero internal or external drive level has been set The GATE position gives normal control of the LED by the gate ...

Page 9: ...l keep re triggering for as long as the power remains above these values For users who at their own risk of course wish to experiment with the overload parameters and or wish to make their own custom LED heads See Appendix CURRENT Controller This is a 10 turn calibrated control which sets the LED drive current when the ext level switch on the rear panel is in the OFF position otherwise control is ...

Page 10: ...witch is in the ON position the feedback loop uses the output of the photodiode amplifier instead so the control voltage now sets the optical output of the LED rather than the current through it Use of this facility is strongly encouraged for critical applications The only downside is that the optical response time for switching purposes is now rather longer although at around 10 micro seconds it ...

Page 11: ...ad time An alternative use of this dual gating is to allow an interlock where one of the inputs has to be actively driven high before the other input can be used A BNC link cable is included with the OptoLED in case only one control input is available MONITOR BNC This is an output signal from a photodiode and its associated amplifier in the LED head The gain of this amplifier is set by a preset re...

Page 12: ...ently being used but has been included to future proof the controller for further development REMOTE Connector This connector is for the optional remote control slider Please note in order to control the unit using the remote control the switch must be in the REMOTE position on the front panel of the unit Page 6 ...

Page 13: ...both jumpers disconnected 2A and 10A Of these 2A is likely to be the most useful alternative The 10A range is not officially specified since amongst other reasons the power supply cannot provide sufficient current except maybe for transients We included it in case LEDs that required such high currents became available but in practice it seems that manufacturers prefer to make more powerful LEDs by...

Page 14: ...high nearly all the time if advanced too far it will suddenly change to a square wave Note that this preset will be need to be readjusted to achieve this condition if PRE4 is adjusted to change the pulse frequency PRE3 This sets the 10V internal reference voltage The most convenient measurement point is the clockwise end front tag of the current control potentiometer PRE4 This sets the frequency o...

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Page 16: ...he basic characteristics of such devices i e they only pass current in one direction and the current rises very rapidly once the voltage in that direction exceeds a certain threshold Ordinary silicon diodes have a threshold voltage of about 0 65V but LEDs have significantly higher thresholds e g around 1 2V for a standard red indicator LED Devices designed for shorter wavelengths tend to have high...

Page 17: ...tentially capable of handling currents of up to 10A Although LEDs may become somewhat less efficient at higher currents their maximum output is ultimately limited not by optical saturation but by thermal dissipation Therefore it is perfectly permissible for an LED to be driven transiently at a higher current than the safe steady state limit The extent to which this can be done i e how much higher ...

Page 18: ...d of the pulse will be somewhat affected but even here the effect is only partial Although the feedback photodiode can in principle be positioned anywhere in the optical pathway the most convenient location is likely to be next to the LED itself The actual LED chip tends to radiate over a wide angular range and although the light may be focussed over a somewhat narrower range by a built in lens ge...

Page 19: ...purposes the more powerful types are clearly to be preferred However for microscope illumination the situation is rather different and in practice better results may be achieved from using a less powerful LED here The reason for this is as follows A high magnification microscope needs to use the condenser or objective in the case of epi illumination to focus the light onto a very small area This r...

Page 20: ...times via hold inputs on or off 100nsec Response time to change in external analogue input 10usec Response time of optical feedback circuit 10usec External analogue control voltage range 0 to 10V Digital inputs TTL level 0V or 5V nominal Overload detection parameters set by components in the LED heads cut out duration during overload 1 sec nominal auto reset Page 15 Page 14 ...

Page 21: ...echnical Support E mail tech cairn research co uk Web http www cairn research co uk Address Cairn Research Graveny Road Faversham Kent ME13 8UP Telephone 44 0 1795590140 Fax 44 0 1795594510 Page 16 Page 15 ...

Page 22: ...ive ground connection to the LED Pin 4 Array signalling connection If this pin is connected to a positive voltage source i e the positive supply voltage for the photodiode amplifier on pin 7 the array indicator on the controller will be illuminated and the power readings on the meter will be reduced by a factor of 10 to allow power levels of 20W or more to be displayed Otherwise this pin should be...

Page 23: ...on as the signal input at the comparator exceeds the reference input this cuts the power for about 1 second If the protection network is just a single resistor overload will be triggered as soon as the power exceeds the value set by this resistor In practice however LEDs can be transiently overdriven and this can be permitted by connecting a second resistor in partallel with the first but with a c...

Page 24: ... red ones The permissible transient power levels may well not be quoted so may need to be determined by trial and error if you want to exploit this possibility Transient levels of 2 4 times the steady state level with a decay time constant of around 10 20msec or possibly a little longer will probably be about as far as we can go For setting a higher transient power overload level another resistor ...

Page 25: ...mple may be helpful in order to give some idea of the typical size of C Let us assume we want a transient power level of 10W declining to a steady state level of 5W with a 10msec time constant From the table we select 68K for R to get 5W steady state power and then select Rp to give a resistance of 24K for R and Rp in parallel to get 10W transient power This requires Rp to be 37K for which the nea...

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