Sutter Instrument Lambda 421 User manual

One Digital Drive
Novato, CA 94949
Voice: 415-883-0128 Web: www.sutter.com
Fax: [phone] Email: [e-mail]
Lambda 421
Ultra-High-Speed Optical Beam Combined
4-Channel Wavelength Switching
LED Light Source System
(With Lambda DG-4 External
Control Compatibility)
Operation Manual
Rev. 1.00n ((20170623)

II
Copyright © 2017 Sutter Instrument Company. All Rights Reserved.

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LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
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DISCLAIMER
The Lambda 421 is a ultra-high-speed wavelength switching multi-LED-based beam
combined illumination or light source device. The purpose of the system is to be an
illuminator for microscopes. No other use is recommended.
This instrument is designed for use in a laboratory environment. It is not intended, nor
should it be used in human experimentation or applied to humans in any way. This is not a
medical device.
Unless otherwise indicated in this manual or by Sutter Instrument Technical Support for
reconfiguration, do not open or attempt to repair the instrument.
Do not allow unauthorized and/or untrained operative to use this device.
Any misuse will be the sole responsibility of the user/owner and Sutter Instrument Company
assumes no implied or inferred liability for direct or consequential damages from this
instrument if it is operated or used in any way other than for which it is designed.
SAFETY WARNINGS AND PRECAUTIONS
Electrical
Operate the Lambda 421 using 110 – 240 VAC., 50-60 Hz line voltage. This instrument is
designed for use in a laboratory environment that has low electrical noise and mechanical
vibration. Surge suppression is recommended at all times.
Fuse Replacement: Replace only with the same type and rating:
4 Amp, 125V, 5 x 20mm, Time Delay fuse (EIC 60127-2)
(Example: Bussmann GMC-4A)
A spare fuse is located in the power input module.
Avoiding Electrical Shock and Fire-related Injury
Always use the grounded power supply cord set provided to connect the system’s
power adapter to a grounded/earthed outlet (3-prong). This is required to protect you
from injury in the event that an electrical hazard occurs.
Do not disassemble the system. Refer servicing to qualified personnel.
To prevent fire or shock hazard do not expose the unit to rain or moisture.
Electromagnetic Interference
To comply with FDA and CE/EU electromagnetic immunity and interference standards; and
to reduce the electromagnetic coupling between this and other equipment in your lab always
use the type and length of interconnect cables provided with the unit for the interconnection
of its components (see the Technical Specifications appendix for more details).
Operational
Failure to comply with any of the following precautions may damage this device.

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Operate only in a location where there is a free flow of fresh air on all sides.
NEVER ALLOW THE FREE FLOW OF AIR TO BE RESTRICTED.
This instrument is designed for operation in a laboratory environment (Pollution Degree
I) that is free from mechanical vibrations, electrical noise and transients.
DO NOT CONNECT OR DISCONNECT THE LQUID LIGHT GUIDE BETWEEN
THE LAMBDA 421 AND MICROSCOPE ADAPTER (OR THE ADAPTER FROM THE
MICROSCOPE) WHILE POWER IS ON.
Operate this instrument only according to the instructions included in this manual.
Do not operate if there is any obvious damage to any part of the instrument.
Do not operate this instrument near flammable materials. The use of any hazardous
materials with this instrument is not recommended and, if undertaken, is done so at the
users’ own risk.
Do not operate if there is any obvious damage to any part of the instrument.
Avoiding Physical Injury while Powered up and Emitting Light
INFRARED AND ULTRAVIOLET RADIATION: Possible infrared and ultraviolet
radiation generated by this lamp can cause significant skin burns and eye damage.
Other
Retain the original packaging for future transport of the instrument.
Sutter Instrument reserves the right to change specifications without prior notice.
This device is intended only for research purposes.
WARNING
DO NOT LOOK DIRECTLY INTO THE OUTPUT OF THE LIGHT
APERTURE OF THE OPTICAL BEAM COMBINER MOUNTED
ON THE CONTROLLER, THE CONNECTED LIQUID LIGHT
GUIDE, OR THE ATTACHED MICROSCOPE ADAPTER! Always
direct the output of the light aperture into the microscope using the
appropriate adapters, directed away from anyone’s eyes, and not
directed toward any reflective surface.

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
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TABLE OF CONTENTS
DISCLAIMER .........................................................................................................................................iii
SAFETY WARNINGS AND PRECAUTIONS ....................................................................................iii
Electrical .................................................................................................................................................iii
Avoiding Electrical Shock and Fire-related Injury.............................................................................iii
Electromagnetic Interference ...............................................................................................................iii
Operational .............................................................................................................................................iii
Avoiding Physical Injury while Powered up and Emitting Light .....................................................iv
Other .......................................................................................................................................................iv
1. INTRODUCTION ...............................................................................................................................1
1.1 Introduction.......................................................................................................................................1
1.1.1 How to Use this Manual............................................................................................................ 1
1.1.2 Technical Support ......................................................................................................................1
1.2 General Description..........................................................................................................................2
2. INSTALLATION .................................................................................................................................5
2.1 Unpacking..........................................................................................................................................5
2.2 Installation Instructions ..................................................................................................................5
3. OPERATIONS.....................................................................................................................................7
3.1 Controls..............................................................................................................................................7
3.1.1 Power Switch ..............................................................................................................................7
3.1.2 Light Source Channel Control Switch (ON/OFF/TTL) .........................................................7
3.1.3 Internal/External Control Switch (INT. / EXT.) ....................................................................7
3.1.4 Dimness/Intensity Control Knob (0-11) ..................................................................................7
3.2 Indicators ...........................................................................................................................................8
3.2.1 Power Light ................................................................................................................................8
3.3 Connectors .........................................................................................................................................8
3.3.1 Light Beam Combiner Output..................................................................................................8
3.3.2 STROBE BNC Connector .........................................................................................................8
3.3.3 DAC BNC Connector .................................................................................................................8
3.3.4 SHUTTER BNC Connector......................................................................................................8
3.3.5 USB Device Interface Connector..............................................................................................8
3.3.6 SERIAL Interface Connector....................................................................................................8
3.3.7 PARALLEL Interface Connector .............................................................................................8
3.4 Operation ...........................................................................................................................................8
3.5 Understanding the Basic Operation of the Lambda 421..............................................................9
3.6 Manual control ..................................................................................................................................9
3.7 Control via the DG-4 Interface......................................................................................................10
4. MAINTENANCE...............................................................................................................................13
4.1 Routine Maintenance .....................................................................................................................13
5. CHANGING LED MODULES .........................................................................................................15
5.1 Making Maximum Current Adjustments Based on LED Module Power Specification..........15
5.2 Adjustment Procedure for Switching between a 5A LED to 1A or 2A: ....................................16
5.3 Adjustment Procedure for Switching between a 1A or 2A to 5A: .............................................17

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APPENDIX A. LIMITED WARRANTY..............................................................................................19
APPENDIX B. FUSE REPLACEMENT.............................................................................................21
APPENDIX C. TECHNICAL SPECIFICATIONS .............................................................................23
APPENDIX D. EXTERNAL-CONTROL COMMAND REFERENCE.............................................25
INDEX ....................................................................................................................................................33
TABLE OF FIGURES
Figure 1-1. Lambda 421 indicators, controls, and connectors............................................................... 2
Figure 1-2. Stages of pass-through and reflection from each input light source................................. 3
Figure 1-3. Lambda 421 combined output based on the pass-through and reflection of each input
light source. ............................................................................................................................... 3
Figure 3-1. Locations of individual indicators, controls, and connectors on the Lambda 421
controller.................................................................................................................................... 7
Figure 3-2. Rear panel of the Lambda 421............................................................................................. 11
Figure 5-1. Power entry module and fuse location on the rear panel of the Lambda 421 controller.21

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1. INTRODUCTION
1.1 Introduction
The Lambda 421 is an illumination system designed for the rapid change of wavelength
derived from up to four light sources of different wavelengths combined into a single beam.
The system comprises of three subsystems: controller, Optical Beam Combiner (ODC), up to
four LED light sources, and power supply. All four subsystems are conveniently housed in
and on one cabinet. For the most part, this manual is organized around those subsystems to
provide you with ready access to information, as you need it.
1.1.1 How to Use this Manual
This manual is organized in a manner that is best suited for the typical manner in which the
reader would learn about the system, and then install, operate, and maintain it. Prior to the
table of contents of this manual is a disclaimer and a series of cautionary and warning notes
– it is important that these be read first. This first chapter provides an overall description of
the system, leaving more in-depth technical information towards the end of the chapter. The
next chapter describes how to install the system, followed by one or more chapters that
provide operation instructions, and ending with a chapter on maintenance. Following the
final chapter are several appendices that provide supplemental information. The installation
chapter covers everything related to installation, from unpacking the equipment as received,
through to ensuring correct installation and operation. The operation chapters cover the two
basic types of user interaction with the system: Manual (local) control and external computer
control. Please take the time to read these instructions to assure the safe and proper use of
this instrument.
1.1.2 Technical Support
Sutter Instrument Company at no charge provides unlimited technical support to our
customers. Our technical support staff is available between the hours of 8:00 AM and 5:00
PM (Pacific Time) at [phone]. You may also e-mail your queries to [e-mail].
Furthermore, as this manual is currently under construction, if there are any areas that you
feel should be covered in detail we would like to hear from you.

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1.2 General Description
CAPABLE OF COMBINING ANY LIGHT SOURCE
ANY SUITABLE WAVELENGTH (LED OR EXTERNAL FILTERED LIGHT SOURCE)
CAN BE PLACED IN ANY OF 4 POSITIONS WITHOUT CONCERN FOR THE ORDER
SELECTION AND BEAM REFLECTION USING SEMROCK-STR FILTERS
Figure 1-1. Lambda 421 indicators, controls, and connectors.
The Lambda 421 beam combiner is a new, patented, concept for combining separate light
sources with different spectra into a single common output beam. Each separate light source
is collimated before entering the optical path through a bandpass filter. The filters for each
light source also function as mirrors that reflect the collimated beams from the previous light
sources. In the diagram below the optical paths are outlined for each position including the
reflections that occur:
Traditionally, combining more than two light sources required the use of a dichroic ladder.
Dichroic mirrors, which switch from transmission to reflection at one point in the spectrum,
allow the combining of separate light sources, provided that those sources do not have
overlapping wavelengths. The downside of this approach is that light sources cannot be easily
changed.
Dichroic ladders also demand careful attention to the order in which the light sources are
introduced into the optical path, to avoid having the light blocked by the next dichroic in line.
Typically, additional bandpass filters must be added in front of each light source before the
dichroic, to select the desired range of wavelengths for each source. Each filter and dichroic
used in the ladder decreases the total light output of the system.

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
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Figure 1-2. Stages of pass-through and reflection from each input light source.
The Lambda 421 was designed to keep the size of the beam combiner small, and the optical
path short and efficient. Thin-film bandpass filters, such as Semrock’s STR, reflect greater
than 90% of out-of-band light. If the band pass of each light source does not overlap, it is
possible to use the filters for both attenuation and reflection the light from the other sources.
By arranging the filters and sources into a pentagon, we were able to combine four light
sources, in a compact design, with lower losses than previously achievable. As an added
benefit, the last position in the optical train does not require any filter, since no other input
reflects from that position. This input can be used with any sort of light source as long as you
are aware of the possible losses if there are filters in use that overlap this light source. The
fifth side of the pentagon becomes the output for the combined sources.
The filters are easily exchangeable and are installed on small sliders inside the core of the
pentagon. Filters and associated light sources can be arranged in any order around the
pentagon.
In the diagram below the position number of each light source is labeled based on the
number of total reflections.
Figure 1-3. Lambda 421 combined output based on the pass-through and reflection of each input light source.

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Notes:
The light from position #0 goes directly to the device output without being reflected. This
position might be preferred for the source with the greatest desired output.
The filter for the fourth light source is not used as a reflective surface and could be
omitted if a broad-band source were desired.
In configurations with fewer than 4 light sources, sources should be filled from lowest to
highest number of reflections to ensure the greatest light output.
The optical path for each input is tilted by 18 degrees relative to the filter for that port.
This will cause a small shift in the band pass toward shorter wavelengths. While it would
be ideal to have a coating optimized for this application, we have found that stock -STR
filters can be used if you correct for the shift in the band pass when selecting the filters.
This lends itself to combining narrow-band sources such as LEDs and lasers with a
broad-band sources such as an arc lamps or white light LEDs. In the case of LEDs,
wavelengths can be shuttered at the speed of the individual source. Sutter Instrument
Lambda 421, HPX, and TLED products can switch in 10-25 microseconds respectively,
making the Lambda 421 one the fastest wavelength switcher on the market.
The Lambda Optical Beam Combiner is designed for flexibility and expandability. Should
your illumination need change over time a simple configuration change, and possibly
additional filters can produce an entirely different output.

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2. INSTALLATION
2.1 Unpacking
The Lambda 421 and associated hardware comes packed in a single carton. The following is a
list of the components found there. If you believe that any of these components are missing
or show obvious signs of damage from shipping, please contact the factory.
Lambda 421 cabinet containing factory-installed power supply, control electronics, four
light source drivers, Optical Beam Combiner (OBC) mounted with up to four different
wavelength LED light sources, front-panel controls, and rear-panel external-control
connectors
The OBC’s four light source inputs has installed an LED module for the following
wavelength (nanometers): 340, 365, 380, 385, 410, 440, 460, 480, 506, 530, 561, 590, 630,
660, 740, 850, 940, or white light. Each channel’s optics (mirror & filter) are especially
installed and aligned according to the LED’s wavelength chosen.
Power Cord
Liquid Light Guide
Liquid Light Guide dovetail with C-mount extension
Small Zeiss female dovetail
USB Interface Cable
9-pin Serial Interface Cable
25-pin Parallel Interface Cable
Manual
One or more additional LED Assemblies containing different wavelength LEDs (if
ordered)
Microscope adapters (if ordered)
2.2 Installation Instructions
1. Turn power switch to OFF (“0”) position.
2. Plug power cable into the mains outlet.
3. Connect the optical output directly to the microscope via the appropriate adapter or to a
liquid light guide, as appropriate.
4. Make sure that all of up to four light sources (LEDs or external) are connected to the
Optical Beam Combiner (OBC) inputs.
5. Ensure that that the right side switch for each channel (Channel 0 through 3) is in the
OFF position.
6. Power up the Lambda 421 rocking the power switch (far right side of the front panel)
upwards in “1” position. A red LED immediately to the left of the power switch will
illuminate when power is on.
7. Refer to the Operations chapter for instructions on turning on the Lambda 421 and
operating the controls on the front panel and making connections to the rear panel.

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WARNING: DO NOT LOOK DIRECTLY INTO THE
LIGHT GUIDE! The output of the light or the light guide should be
directed into the microscope using the appropriate adapters, directed
away from anyone’s eyes, and not directed toward any reflective
surface.

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
7
3. OPERATIONS
This chapter describes the operation of the Lambda 421. The locations of the individual
indicators, controls, and connectors are indicated in the following figure.
Figure 3-1. Locations of individual indicators, controls, and connectors on the Lambda 421 controller.
3.1 Controls
3.1.1 Power Switch
Main power switch turns unit off/on.
3.1.2 Light Source Channel Control Switch (ON/OFF/TTL)
This is a three-position toggle switch that is used to manually turn the LED on, off, or
activate TTL switching through the STROBE BNC connector.
ON: Manually turns on the channel for manual control.
OFF: Turns off internally generated light source and control for the channel. Does not affect
externally supplied light source.
TTL: Internally supplied LED light source on/off state is controlled by TTL triggering (via
STROBE).
3.1.3 Internal/External Control Switch (INT. / EXT.)
This two-position toggle switch is used to determine whether the internal light source for the
channel is controlled manually (front panel) or externally (via an interface to a computer)
turn the LED on, off, or activate TTL switching through the STROBE BNC connector.
3.1.4 Dimness/Intensity Control Knob (0-11)
This rotary knob dims or intensifies the light source for a given channel by adjusting the
current delivered to the internally-powered LED. Current control may cause color shift in the
LED’s spectral output. However, current-controlled dimming may be preferable in situations
involving the use of ultra high-speed cameras. For the CURRENT knob to be effective, the
LED Control Switch must be set to ON or TTL.

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3.2 Indicators
3.2.1 Power Light
A power light is located to the left of the power switch on the front panel, and is illuminated
when the power is on.
3.3 Connectors
3.3.1 Light Beam Combiner Output
Provides the interface between the combined light source output to a microscope or liquid
light guide.
3.3.2 STROBE BNC Connector
3.3.3 DAC BNC Connector
3.3.4 SHUTTER BNC Connector
Inputs a triggering signal for opening and closing a SmartShutter (if installed), installed for
interference of the Lambda 421’s combined light output.
3.3.5 USB Device Interface Connector
Provides the interface for controlling the Lambda 421 by computer via USB connection.
3.3.6 SERIAL Interface Connector
Provides the interface for controlling the Lambda 421 by computer via 9-pin serial
connection.
Note that the USB interface is mutually exclusive with the SERIAL interface. The USB
interface is enabled at the factory when the Lambda 421 is shipped, unless the SERIAL
interface is specifically requested. When the USB interface is enabled, the SERIAL interface
cannot be used, and vice versa.
3.3.7 PARALLEL Interface Connector
Provides the interface for controlling the Lambda 421 by external means via 25-pin parallel
connection. External control via the parallel interface can be accomplished by TTL (8 lines)
or by connecting to the PARALLEL port of a computer using specialized software.
3.4 Operation
The Sutter Optical Beam Combiner (OBC) installed on the Lambda 421 allows for up to four
light sources with differing spectral output to be combined and delivered on a common
output light path. While OBC has many possible uses, the Lambda 421 provides a means by
which one can rapidly select any one of up to four different LEDs as the output. This sort of
rapid selection of wavelength is what another Sutter Instrument product, the Lambda DG-4,
was designed to do. The DG-4, a popular light source for imaging for many years, is widely

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
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supported by imaging software. The DG-4 circuit board was adapted to control the selection
of the active LED and the operating current for that LED.
The new Lambda 421 system combines four of our high power LEDs and their drivers, a
control circuit board from the new USB version of the DG-4 and the OBC to form a compact,
complete light source that functions like a DG-4 without any moving parts.
3.5 Understanding the Basic Operation of the Lambda 421
3.6 Manual control
The 421 has four LED controllers based on the Sutter Instrument Lambda TLED+
controllers. All of the basic controls of the TLED+ are maintained in the 421. First, there is a
system power switch located on the right of the cabinet face. Next to the switch is an
indicator lamp that shows red when the power supply is in operation. The controls for the
four LED drivers are arranged in four groups, each labeled CHANNEL 0 through CHANNEL
3. The channel number ties into the optical configuration in that it represents: The number
of reflects required to reach the common output port. The apparent incongruity of the 421’s
scheme vs. the DG-4’s Filter 0 is considered a shutter function and the 4 selectable optical
paths are numbered 1-4, is resolved by the arrangement of the 421’s front panel’s controls
and a somewhat altered set of external control commands.
Each channel has a two selector switches and a knob on the front panel. The right-most
switch in each group is labeled ON/OFF/TTL from top to bottom. Selecting the middle
position (OFF) turns the LED off. Setting the switch to the top position (ON), turns the on.
When selecting the lowest position (TTL), the channel is controlled by the DG-4 interface
circuit board. The switch to the left is labeled INT./EXT. In the upper position (INT.), the
internal current reference is selected. In the lower position (EXT.), the current level is under
the control of the DAC setting for whatever filter value is currently selected.
Selecting ON or OFF, and INT., the output is completely under manual control. Select TTL
and EXT., the unit is under control of the DG-4 interface. One can also use a combination of
manual and automatic switch setting if desired. For instance:
If selecting TTL and INT. for a particular channel, the LED turns on and off under
control of the DG-4 interface, but the DAC output setting for selected filters has no effect
on this channel.
If selecting EXT and either ON or OFF for a particular channel, the DG-4 interface will
not control the channel if the channel is gated on or off, but the current for the channel
will be controlled by the DAC setting for the currently selected filter.
The knob for each channel offers the ability to manually attenuate the current. The
attenuation is active no matter what mode or combination of modes is used so long as the
channel is turned on by the logic or the manual switch. If the EXT. mode is used and the DAC
values have reduced the current, the knob will further reduce the current proportionally, as
it would in any other mode.
The 421 was designed for LEDs that required 5 amps for maximum output. In some cases it
is desirable to use LEDs with a lower maximum current. Often certain desirable wavelengths
are not available in the more potent packages. The driver circuits can be turned down to
whatever reduced value of maximum current is required. The DAC input and the knob will

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
10
still further reduce the current proportionally so their operation will be appear to be the
same as the other channels even though the range of currents available has been reduced.
3.7 Control via the DG-4 Interface
In order to understand the Lambda 421 it is important to know the way the DG-4 functions.
The DG-4 selects one of 4 filter paths for the light source. The filter values, in the DG-4
context, are actually just memory locations for the settings assigned to a filter value for
positioning the two galvanometers in the optical system. These settings could be any value in
the range of 0 to 4095. There are 16 available filter values in the DG-4 command set. Filter
values can be any number from 0 to 15. Filter 0 is normally reserved as a shutter function
and may have 0 stored for both galvanometers. Filters 1, 2, 3, and 4 typically have settings
that deliver the light through one of the four physical optical filters to the output port at full
power. Filters 5-12 are typically programmed to select one of the four filter paths at reduced
power. The standard setup uses filters 5-8 to select the filters used in 1-4 at 50% output
power and 9-12 are 1-4 at 33% output power. Filters 13-15 are available but normally defined
at the factory.
We have produced the same sort of control for four LEDs using the new USB DG-4 board.
This approach produces an LED version of the DG-4 that will run with existing software that
supports the DG-4. Since the DG-4 only works with one filter active at a time this command
set does not allow computer selection of more than 1 LED at a time. We have added some
basic logic circuits that convert the value of the filter selected to a signal that activates a
specific LED driver. Each LED is gated by a logic level signal and all LEDs will have the
analog input connected to the common DAC output on the DG-4 circuit board.
Since only one LED is activated by the DG-4 control at a time we can use a single DAC to
supply the current-controlling analog voltage for all four LEDs. In the DG-4 this DAC is
normally used for setting a galvanometer command signal. The DAC value is automatically
set to a value associated with a given filter when that filter is selected. We simply connected
that DAC output to the analog current control inputs of all 4 LED drivers and we now have a
system that automatically sets the desired current for each LED as it is selected. The value
for the DAC can be stored and read back using simple software commands.
The logic level signals that active the correct LED for each filter value are derived from the 4
bit binary output normally logic level output used by the DG-4 to indicate the selected filter.
We have added logic that converts the binary filter value into four separate TTL level
outputs, one for each LED. The original binary output is also available as before. The logic
was designed so that filter values 1-4 select the corresponding LEDs, 1-4. Filter values 5-8
and 9-12 also select LEDs 1-4. Filter values 13-15 select LEDs 1-3. Filter value 0 turns off all
LEDs. Looking at this in another way:
LED 1 is activated by filter values 1, 5, 9 and 13.
LED 2 is activated by filter values 2, 6, 10 and 14.
LED 3 is activated by filter values 3, 7, 11 and 15.
LED 4 is activated by filter values 4, 8, 12
Filter 0 does not active any LED.
The DG-4 controller stores two DAC values for each of the 16 possible filter values. We have
connected the analog output of one of these two DACs to the analog current control input for

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
11
all of the LEDs. When you select a particular filter value you will therefore activate the LED
that corresponds to that filter value but you will also set the voltage for the current control
to the value that corresponds to the DAC setting set for that filter value. We will likely store
DAC values for each filter value according to a scheme similar to the DG-4, but this can
easily be changed. Thus, LEDs 1, 2, and 3 have four different programmable current levels
selected by calling the correct filter value. LED 4 only has three separate values and there is
only one value for OFF: Filter 0.
When operating the Lambda under full control of the DG-4 interface you would set each
channel to TTL control and EXT. current control using the front panel switches. The current
control knobs can be used to attenuate the output of any channel, if desired. The control of
the LEDs then is entirely from the DG-4 interface. The connections for the DG-4 interface
are all available on the back panel.
Figure 3-2. Rear panel of the Lambda 421.
The USB interface to a control computer is the default method of control. In most cases the
USB port will be used in the virtual com port mode which enables this port to support
software that was developed for use with serial port control. There is also a true RS232 serial
port, but this cannot be used at the same time as the USB port. Selecting which of the two
ports is active will be discussed elsewhere. The other option for full control is the parallel
port. While this input provides very short latency few systems offer the full 8 bits needed to
input all types of commands. This port is not fully bi-directional, so it does not allow reading
settings back to the computer. The most common use of the parallel port is for rapid selection
of the active channels via individual TTL signals, as will be discussed elsewhere.
FILTER VALUE OUTPUT RJ-45 Receptacle

LAMBDA 421 OPERATION MANUAL – REV. 1.00N (20170623)
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In addition to the computer interfaces, there is the Strobe input, which is used as a trigger in
the ring buffer mode. There is an analog output and a digital output that are both used to
indicate the currently selected filter. The analog output (DAC) produces a voltage of 0 to 6
volts in 16 steps. Each increment in the filter value adds 0.4 volts to the output voltage. The
digital output is a binary representation of the currently selected filter number.
Table 1. Selecting channel light source intensity via external-control filter value commands.
FILTER
VALUE
LED
SELECTED
SUGGESTED
CURRENT
0 NONE 0%
1 1 100%
2 2 100%
3 3 100%
4 4 100%
5 1 50%
6 2 50%
7 3 50%
8 4 50%
9 1 33%
10 2 33%
11 3 33%
12 4 33%
13 1 15%
14 2 15%
15 3 15%
The actual attenuation is determined by the DAC value associated with each filter value.
These are programmed as indicated in the previous table. However, each value can easily be
changed from external software.
The new Lambda 421 has a new series of trigger options for the ring buffer. Triggering on
the rising edge or the falling edge of the trigger signal can be selected. A special mode that
allows the level of the trigger signal to also control the shutter function is also available. This
allows a typical shutter control signal to advance the filter selection in the ring buffer while
also controlling the on/off state of the light.