Sphere lab technical info

Sphere lab

Sound booth

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Computer

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Electronics rack

upper half of electronics rack

zBus Monitor

The upper half of the electronics rack contains 10 TDT Zbus devices chassis, each containing two TDT series 3 devices. The lower half contains the Field coil amplifier and the Femto LockinAmplifier as part of the head tracking electronics.

The zBus Monitor program has control functions for the optical bus. It shows all the connected zBus chassis and the TDT devices that are installed in each chassis. It also shows the version number of the installed firmware on the devices.

The following table shows all the zBus chassis from top to bottom, with the installed devices.

Chassis	Front left	Front right	Back
Zbus	MS2 Monitor speaker	<empty>
Zbus	PA5 Attenuator	PA5 Attenuator	F05 optibit bus #1
Zbus	PA5 Attenuator	PA5 Attenuator	F05 optibit bus #2
Zbus	SA1 Speaker amplifier	SA1 Speaker amplifier
Zbus	RP2.1 Sound processor	RP2.1 Sound processor	F05 optibit bus #3
Zbus	PM2R Multiplexer	PM2R Multiplexer
Zbus	PM2R Multiplexer	PM2R Multiplexer
Zbus	PM2R Multiplexer	PM2R Multiplexer
Zbus	PM2R Multiplexer	PM2R Multiplexer
Zbus	RA16ba base station	RA8GA2 multi DAC	F05 optibit bus #4

The next list shows all other electronics in the lower half of the rack from top to bottom.

• PP16 Patch panel for Medusa Base Station (2x)
• Digital event recorder
• Junction box panel (connects to junction box in sound boot)
• Trigger distribution panel
• Femto Lockin amplifiers
• Tektronics Oscilloscope
• Field coil amplifier
• Rack main power switch
• Patch panel for XLR output to Tannoy speakers

Sound system

Connection schematics of the sound system

Speaker locations on the sphere

The sound system consists of two programmable DSP’s (TDT RP2.1’s) with each two DAC’s. An RP2.1 generates a sound signal that travels via a programmable attenuator (TDT PA5), a stereo amplifier (TDT SA1) and a multiplexer (TDT PM2R) to a patch panel inside the PLC cabinet in the boot and from there to a speaker. The multiplexing system consists of two sets of four multiplexers (TDT PM2relay). Each multiplexer has 16 channels. Only one channels per multiplexer can be opened at a time. The total number of channels is 128. Each RP2.1 controls four multiplexers. Since each RP2.1 has 2 DAC outputs, each output is connected to two multiplexers. It is therefore possible to play up to 4 different sounds at once over different speaker. Parts

• TDT RP2.1 (2x)
• TDT PA5 (4x)
• TDT SA1 (2x)
• TDT PM2relay Multiplexers (8x)
• Flat cables from RP2.1 to PM2relays (2x)
• Dsub25 cables from PM2relays to PLC cabinet in the boot (8x)

• Patch panel inside the PLC cabinet
• Speakers (116x)

Minx12 speaker system

Speaker (and LED) connection scheme

The Minx12 speakers are connected via 5 lead wires with a 5 pole binder connector at each end. Two leads are used for the speakers, three leads are used for the LED’s.

Tannoy speaker system

XLR patch panel connection scheme

LED system

PLC output scheme (only 2 outputs indicated)

The LED system consists of a cabinet inside the sound boot with a Panasonic FP2 series PLC system (programmable logic controller). The PLC can independently switch 256 channels. The channels connect to a two color LEDs (red and green) that are mounted on the speaker. The PLC cabinet has two test buttons that can light all LEDs at once. The PLC system consists of a PLC with several IO units and is can be programmed by via a special USB cable.

Parts

• Trigger from Medusa base station
• PLC cabinet (houses PLC system)
  • FP2 PLC system from Panasonic
  • Break-out panel with 5 pole Binder connectors (128x)
• Binder cables (120x)
• LED mounting frames (120x)
• Red/Green LED’s (120x)
• Trigger converter (5V → 24V) for input trigger
• Trigger converter (24V → 5V) for trigger echo

Specifications Panasonic FP2 series

• FP2C2LJ FP2SH PLC
  • 1 ms cycle time when <20.000 steps per cycle (120.000 steps max)
  • Measured cycle time 1.35 ms
• FP2Y64TJ output unit (4x)
  • 64 channels
  • 24V NPN output
  • Current 0.3A max
  • Response time <0.3 ms
• FP2PXYPJ multi I/O unit
  • PNP transistor
  • PWM output 30 kHz
  • Duty cycle 0-100% in steps of 1%
  • Max output 800 mA
• FP2X16D2J input unit
  • 16 channels
  • Current 8 mA @24V
  • Response time <0.2 ms

Specifications Red/Green LEDs

• Bivar 5BC-3-CA-F (Common Anode)
• Red 625nm (FWHM = 25 nm)
• Green 568 nm (FWHM = 30 nm)
• Nominal current 20 mA
• Voltage drop 2.1V
• 45 degree viewing angle
• Series resistor 1kOhm
• Actual current 10 mA @100% PWM

Trigger/Timing system

LED stimulus in standard modus (X=0)

LED stimulus in short pulse modus (X=1)

Description

The task of the trigger/timing system is to distribute trigger signals and record the timing of the triggers. In the standard situation when an experiment starts, the subject has to push a button to start a trial. The button push is registered by an arduino trigger bridge that outputs a trigger to the Medusa Base Station. The Medusa sends triggers to the RP2.1’s, the LED PLC and to the Event Recorder. The Event Recorder timestamps all the triggers and can be read out via ethernet. The arduino trigger bridge has a green LED that indicates that a trigger signal is generated and it has a test button that generates a trigger signal when pushed.

Parts

• Pushbutton
• Arduino trigger bridge
• Patch Panel PP16
• Medusa Base Station (TDT
• Event Recorder

Specification

The LED PLC in the LED controller cabinet can be programmed by Matlab. The PLC stores a list of LED configurations. One configuration tells the PLC which LEDs should be on or off. In the standard mode (X = 0) the current configuration is changed to the next configuration by an electrical trigger signal. A stimulus of a single LED consists of two configurations, one with only that LED on, followed by one with all the LEDs off. The timing and the length of the stimulus are controlled by trigger signals sent from the Medusa Base Station. The PLC cycle of 1.35 ms is the limiting factor for the shortness of a LED stimulus. In practice the pulselength can be as short as two or three PLC cycles (2.7 ms or 4.0 ms) in the standard modus (X=0). The number of cycles the stimulus lasts can vary by one cycle. In practice there is always 1.35 ms jitter on top of a 1.35 ms delay for the start (and end) of a LED stimulus (see figure). When more precise knowledge is needed over the timing or length of the stimulus, a timing signal (trigger echo) sent from the PLC can be recorded. The trigger echo signal is lined up with the rising or falling flanks of the LED and can measure the real stimulus with an accuracy down to 40 µs.

When using short stimuli the X parameter can be used to control the exact number of cycles. When X = n the length of the LED stimulus is exactly n PLC cycles.