Plexon HELIOS Quick start guide
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HELIOS®Technical Guide
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HELIOS®Technical Guide
Contents
3 Introduction
3 Components
3 Overview
4 Charging the HELIOS device
5 Connecting the Transmitter
6 Pattern Generation
8 Setting the Power Output
9 Pulse Parameters
10 Advertised Maxium Power
10 Battery Life
11 Transmission Latency
11 Transmission and Receive Angles
12 Transmission Range and Interference
Documentation History
Date Version Notes
December 2107 OPTMN0002a Document Created
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Introduction
This document will provide a description of the HELIOS (Head-mounted Extra Light Infrared Optogenetic
Stimulation) Wireless System components and instructions for proper usage. The HELIOS system contains
the HELIOS Infrared-Controlled Head Mounted LED (IR-Controlled HMLED), the Infrared (IR)
Transmitter, a charging kit and ceramic sleeves. These items can be purchased as a kit or separately.
This guide will discuss components of the system, battery life, transmission range, and setting pulse
parameters.
Components
The HELIOS® Kit is for using an infrared-controlled head-mounted LED and consists of the (1) HELIOS IR-Controlled
HMLED, (1) IR Transmitter, (1) charging kit, and ceramic sleeves.
Overview
Fiber Stub Implants purchased
separately
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Charging the HELIOS Device
The IR-controlled HMLED has a rechargeable Lithium Polymer battery. When the battery voltage drops
below 3.3V, a red LED on the top of the HMLED will start to
ash, indicating that the battery will need to be recharged
shortly. However, the battery voltage can also droop during high
output pulses, which may make the low battery indicator blink
prematurely.
Note: You do not necessarily need to stop your experiment immediately as soon as the red light begins to
ash. The amount of time that you can continue to run your experiment will depend on the pulse width,
amplitude, and duty cycle.
To charge the HMLED:
1. Slide the HMLED power switch to the green position.
CAUTION: Proceeding without ensuring the power switch is in the green position can cause
irreparable damage to the charger.
2. Attach cables to the charger by plugging the micro-USB cable connector (a) into one side of the
charger (b) and the two wire connector of the charging cable (c) into the other side.
3. Plug the 3 pin connector on the charging cable (c) into the plug on the
HMLED. Make certain that all three pins are connected.
CAUTION: Proceeding without ensuring all three pins are connected
will cause irreparable damage to the charger. The polarity of the 3 pin
connector is not important.
4. Plug the other end of the USB cable (a) into a standard (type A) USB port.
5. Slide the power switch on the HMLED in the red position for charging.
*A red light on the charger (b) indicates that the battery is charging. It will go o when charging is
complete.*
Note: The battery will charge quickly at rst, and then slowly as it approaches full capacity. If you charge
an empty battery, the red light will be on solid (fast charging) for approximately 15 minutes. This will
charge the battery to approximately 70% of its full capacity. Charging an additional 45 minutes (total 1
hour) will charge the battery to approximately 90% of its full capacity, during which time the red LED will
blink regularly. Charging the remaining 10% capacity can take several hours, and is seen by the red LED
sporadically blinking. The red light will turn o when the charge is at 100%. It is not necessary to charge
the battery to exactly 100%, but it is recommended (for battery life).
6. Remove the USB cable from the USB port
7. Remove the three-pin connector from the HMLED. (Store the charging kit in a safe
place for future use.)
a
c
b
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Connecting the Transmitter
The IR-controlled HMLED is turned on by a signal from the Plexon IR transmitter, shown in the images
below.
In the above image, notice that there is a mark next to the letter“A”. The letters B, C, and D are reserved
for future use.
The transmitter is on whenever +5V is applied to its BNC connector. There are multiple ways apply the
+5V, but the easiest is to use the Plexon PlexBright 4 Channel Optogenetic Controller in voltage mode
and Radiant software to congure a pattern. The procedure below uses Channel 1 on the optogenetic
controller to apply a pulse through the HMLED.
CAUTION: You must NOT attempt to use the Transmitter with any current-based controller, such as
the Plexon PlexBright LD-1 Single Channel LED Driver. The only safe way to use the Transmitter is with
a voltage-based driver that can be set to generate 0V or +5V. The Transmitter is on whenever +5V is
applied to the BNC connector.
1. Slide the power switch on HMLED to the green (on) position.
The LED is turned o in the red position.
2. Turn the white power level dial on the top of
the HMLED fully counterclockwise, which will be the minimum
output.
3. Connect the transmitter to Channel 1 on the Optogenetic Controller using a BNC cable or optional BNC
male-to-male adapter .
CAUTION: While any BNC cable can be used for stimulation, with each optogenetic controller,
Plexon provides insulated BNC cables that prevent the outer contacts from touching. We recommend that
you use one of these cables.
4. Position the Transmitter so that there is a direct line of site between the transmitter and the HMLED.
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Pattern Generation
These directions will result in a 10% duty cycle with a continous pulse pattern To calculate the duty cycle,
divide the “on” time by the period 10ms/100ms = 10%.
Note: For a complete description of the stimulation patterns that can be achieved with the Optogenetic
Controller, see the PlexBright® 4 Channel Optogenetic Controller with Radiant™ Software User Guide on
the Plexon website.
1. Verify that the digital input mode (DI Mode) is set to Single Function, and the DI Polarity to Positive.
(These are the default values.)
2. Set Channel 1 to LASER mode.
3. Set Output Mode to Voltage (mV).
4. In the Pattern Generator window, add a new pattern (+P). Set Pattern Units to Laser (mV) and set
Repetitions to Continuous.
CAUTION: In the Channel Settings, you MUST Set Output Device to LASER and set the Output Mode to
Voltage (mV). In the pattern Generator, you MUST set the Units to Laser (mV). Failure to do so can cause
excessive power levels in the HELIOS Transmitter, resulting in irreparable damage to the Transmitter
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5. Add a new Group (+G). Set the Period to 1000ms and Count to 1.
You can set these parameters to other values appropriate to your experiment.
6. Add a Primitive (Pulse).
7. Set Value to 5000mV and Pulse Width to 10ms. Ensure the period is set to 100ms. Then, set the
repetition number to 10 for the primitive to repeat 10 times.
You should always set the Value to 5000mV. You can set the Pulse Width to any value appropriate to your
experiment.
Note: The HMLED is intended to be used with short pulses of light. In fact, leaving the LED on for
extended periods will cause the LED to heat up and will drain the battery. Therefore, we recommend that
you limit the duty cycle (the percentage of time that the LED is illuminated) to 10%, if possible.
8. In Channel 1’s window, change Pattern Source to Pattern Generator and select Pattern 1 as the Pattern.
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Setting Power Output
Before starting your experiment, you will need to adjust the power output to your desired level. This can
be done using the Light Measurement Kit and Plexon Photodetector adapters. For a complete description
see the PlexBright Light Measurement Kit guide on the Plexon Website.
You will need to generate a pattern prior to setting your power output. The directions for setting the
power output will use the example from page 6 of this guide which generates a pattern with a 10ms pulse
and a period of 100ms, resulting in a 10% duty cycle.
1. Ensure that the power switch on the HMLED is on the green position.
2. Since the example pattern previously generated uses Channel 1, press the
Play button for Channel 1 to start stimulation.
3. Connect the appropriate photodetector adapter (LC or FC) to your light measurement kit and place the
tip of HMLED into the adapter
Note: Because the white power-level dial on the HMLED was turned fully counter-clockwise in the
“Connecting the Transmitter” section of this guide, the LED should not turn on yet.
4. Remove the HMLED from the adapter and slowly turn the white power-level dial on the HMLED
clockwise to increase the LED power.
5. Repeat these steps until the desired power level is reached. Use the lowest acceptable power to
improve battery life and reduce heating of the LED.
You can approximate the pulse power of the LED with the LCD display of the Light Measurement Kit. For
example, if the display says 4mW, the actual pulse will be approximately 40mW (for the 10% duty cycle
used in this example).
Note: If you have an oscilloscope available, connect it to analog output of the light
meter. The oscilloscope will be used to display the instantaneous light power output of
the HMLED and will allow you to accurately adjust the power dial on the HMLED. As the
LED pulses, you should see corresponding pulses on the oscilloscope. Adjust the dial
until the desired power level is reached.
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LED Pulse Parameters
The HMLED can use a large amount of current when delivering very intense pulses of light. Shorter pulses
with low duty cycles can deliver the most light. As you extend the pulses or increase their frequency, the
current driving circuitry in the HMLED will no longer be able to deliver “good” pulses. A good pulse has a
square shape and maintains the output for the duration of the pulse. An example of a good pulse as seen
on the light meter is shown below.
The example above is a blue 465nm LED pulse being delivered at 1Hz. When setting up the power
meter, you will see that the maximum power it can register is 140mW, which is displayed as 2V on the
oscilloscope. Since this pulse is 660mV, you can calculate light power as 140mW*0.660V/2V = 46.2mW.
The chart below shows the maximum pulse intensity that can be delivered as a function of pulse duration
and duty cycle. Note that above duty cycles of 10%, the maximum intensity begins to drop. Therefore,
Plexon recommends keeping the duty cycle below 10%. Referring to the chart below, the 10ms pulse from
above is graphed by the red line. Any point under that line should be a good pulse. 46.2mW at 1% duty
cycle is well below the red line and is a good pulse.
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Advertised Max Power
Below are minimum expected power outputs when using 1ms pulses with 1% duty cycle. In practice, many
pieces will have higher output power.
Blue (465nm): 55mW
Green (525nm): 15mW
Orange (620nm): 24mW
Lime (550nm): 22mW
Battery Life
The battery life is highly dependent on the intensity of the pulses being delivered and their duty cycle. To
maximize battery life, the lowest acceptable intensity and duty cycle should always be used. One way to
characterize the HMLED is in mWh (milliwatt hours). This is how many milliwatts of light can be delivered
continuously for an hour. Remember though that the HMLED is not meant to be operated continuously.
The approximate mWh for each color is shown below. These values are based on minimum power
outputs.
Blue (465nm): 2.3mWh
Green (525nm): 0.63mWh
Orange (620nm): 1.0mWh
Lime (550nm): 0.92mWh
To estimate how long a battery will last with a particular pulse pattern, you need to divide the mWh of the
module by the pulse amplitude multiplied by duty cycle.
As an example, if you are using a blue HMLED, delivering 15mW pulses with a 5% duty cycle, the battery
will last approximately 2.3/(15*0.05) = 3 hours. If you double the duty cycle, the battery will last half as
long. Again, this is only intended to be an estimate for battery life. This assumes that the pulses are
square and succesfully delivered.
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Transmission Latency
There is approximately 280us between when the Optogenetic Controller digital output goes high,
signifying that the transmitter is turned on, and the LED turning on. A similar delay is seen when turning
o the LED. This is shown in the screenshot below. The yellow trace is the light power from the meter.
Transmission and Receive Angles
The IR Transmitter emits the signal in a wide arc, but it is not omnidirectional. The infrared light is emitted
in the pink zone in the picture below. The HMLED must fall within this zone to receive the signal. In many
experimental setups, the transmitter can be mounted with the circuit board parallel to the top of the
enclosure and the entire area that the animal can enter will be illuminated. For particularly short or wide
enclosures, the transmitter can be mounted vertically as well.
In the plane of the circuit board, the board will block the infrared light, so it is only transmitted outward in
the direction shown below.
The HMLED will receive IR light from almost any angle above the plane of the circuit board. The battery
blocks a few degrees of reception, and it will actually receive light from slightly below the circuit board on
the opposite side.
About Plexon Inc
Plexon is a pioneer and leading innovator of custom, high-performance data acquisition, behavior and analysis solutions specically designed
for scientic research. We collaborate with and supply thousands of customers including the most prestigious neuroscience laboratories
around the globe driving new frontiers in areas including basic science, brain-machine interfaces (BMI), neurodegenerative diseases, addictive
behaviors and neuroprosthetics. Plexon oers integrated solutions for in vivo neurophysiology, optogenetics, and behavioral research – backed
by its industry-leading commitment to quality and customer support. For more information, please visit www.plexon.com.
Sales Support
For Sales Support, email info@plexon.com or call +1 (214) 369-4957.
Technical Support
If after reviewing this document, you would still like to access Plexon’s Technical Support, we are available via several communication channels.
You are invited to reach us through email or on the phone:
EMAIL PHONE
+1 (214) 369-4957
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PLEXON®, Plexon®, the ve-line symbol, CereStage™, CineCorder®, CineLAB®, CineLyzer®, CinePartner™, CinePlex®, CineTracker®,
CineTyper™, DigiAmp™, MiniDigi™, Oine Sorter™, OmniPlex®, PL2™, PlexBright®, PlexDrive™, PlexSort®, PlexStim™, Plextrode®,
Radiant™, RapidGrid™, TrackSort® and the Plexon logo are trademarks of Plexon Inc, Dallas, Texas, USA. Other product and company names
mentioned are trademarks of their respective owners.
OPTMN0002a
Transmission Range and Interference
The wireless transmission range is dependent on the angle that the light is hitting the receiver. As you
approach the dark green and dark red lines in the images above, the transmission range drops o. As a
general rule, the transmitter should be placed as close to the HMLED as possible. At a distance greater
than 2 feet, the receiving angle begins to signicantly narrow.
The range is limited by the amount of current that can be driven to the transmitter in voltage mode. If an
enclosure is particularly large, multiple transmitters could be placed around it to increase the coverage.
You would then use multiple channels on the Optogenetic Controller, congure them all for the same
pattern, and use the start all command to trigger them.
Some LCD computer monitors emit sucient IR light at 38kHz to trigger the HMLED to turn on. The
touchscreen inside the Bussey chamber also can turn on the HMLED, so at this point it will not work inside
the Bussey chamber.
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