OpenBCI · complete 16-channel setup

Gel Electrode Cap Manual

Follow the six stages in order to assemble the Cyton–Daisy system, map the cap, apply gel, verify all channels, record safely, and clean up correctly.

Portrait in the research lab beside a social robotRAP Lab · bench manual
MAIN BOARDCyton powers and controls the system; it supplies GUI channels 1–8.
EXPANSIONDaisy adds eight inputs, producing GUI channels 9–16.
REFERENCEBoth SRB pins share cap REF; Cyton BIAS alone connects to cap GND.

Start here: the complete setup path

Work from left to right. Finish each stage before moving to the next; the numbered sections below provide the exact checks and photographs.

01

Understand the system before touching the pins

The simplest mental model: Cyton is the computer and first eight channels; Daisy is an eight-channel extension. The cap supplies labeled scalp positions. HPTA leads adapt the cap’s touch-proof plugs to board header pins.

Cyton is primary

Battery socket, radio, processor, power switch, BIAS, SRB, and channels 1–8 live here.

Daisy adds channels

It stacks on Cyton and adds channels 9–16. It is not the main controller.

Bottom inputs only

Use the specified bottom N1P–N8P, SRB, and Cyton BIAS pins for this cap setup. The upper headers are not cap EEG inputs.

Before a human participantUse an approved study protocol, informed consent, and trained supervision. Power the system from its compatible battery while connected to a participant; never charge it on a participant and never wire mains power directly to the board.

What you need

RECORDINGCyton + Daisy stack, USB dongle, compatible inspected LiPo battery, laptop with OpenBCI GUI.
CAPCorrect-size 19-position gel electrode cap, electrode gel, blunt syringe/applicator.
WIRING16 channel HPTA leads, one HPTA for REF, one HPTA for GND, and the CytonDaisy Y-splitter.
CLEANINGWarm clean water, cotton balls, drying rack; deionized or distilled water if available.
HPTA leads. Wire color is only an identifier; it does not define a scalp location.
Cap leads. The printed labels—Fp1, F3, O1 and others—define scalp positions.
Y-splitter. Its two legs gang the SRB pins; its single end continues to REF.
HPTA adapter. The header end meets the board or Y-splitter; the touch-proof end meets the labeled cap lead.
Cap lead bundle. Separate and read each printed 10–20 label before assigning a channel.
Stack orientation. Daisy sits on top; Cyton underneath remains the powered main board.
02

Assemble and wire the boards

Do this with the Cyton switched OFF and the participant disconnected. Follow the three signal paths: reference, bias/ground, then 16 recording inputs.

The entire wiring logicCyton SRB + Daisy SRB → Y-splitter → cap REF
Cyton BIAS → cap GND
Cyton N1P–N8P → GUI 1–8 · Daisy N1P–N8P → GUI 9–16
Cyton · main board
SRBN1P…N8PBIASAGNDAVDD
SRBY-SPLITREF
Daisy · expansion
SRBN1P…N8PBIASAGNDAVDD

Stack Daisy on Cyton

Align and seat the Daisy squarely on the Cyton headers. Cyton remains the lower/main board; Daisy is the upper extension.

Join the bottom SRB pins

Put one Y-splitter leg on Cyton’s bottom SRB pin and the other on Daisy’s bottom SRB pin. Never put the Y-splitter on N1P.

Continue the single end to cap REF

Attach one HPTA lead to the Y-splitter’s single end. Connect its blue touch-proof end to the cap lead labeled REF.

Connect cap GND to Cyton BIAS

Use one HPTA between the cap’s GND lead and the Cyton’s bottom BIAS pin. Leave Daisy BIAS empty.

Connect the 16 channels

Place eight HPTA header ends on Cyton N1P–N8P and eight on Daisy N1P–N8P. Push straight down until each black housing is fully seated.

Leave non-signal pins alone

For this cap setup, AGND and AVDD on both boards stay empty. Daisy BIAS also stays empty. Do not place electrodes on board power rails.

Direction and seating. Connectors sit straight over individual header pins; trace each wire from pin to blue cap plug.
If a pin slips out. Power off. Reinsert until the small locking tab clicks. If the tab is flattened, gently lift it before reinserting; replace a broken terminal.
Daisy wiring. N1P–N8P carry GUI channels 9–16; SRB takes one Y-splitter leg.
Daisy pin direction. Seat each single-pin housing straight over its labeled bottom-row pin.
Bench stop-checkOn Daisy, N1P–N8P are channels, SRB is the Y-splitter branch, and BIAS / AGND / AVDD remain empty. On Cyton, only BIAS receives cap GND; AGND and AVDD remain empty.
03

Choose and document your 16 scalp positions

There is no required color-to-electrode pairing. Choose the cap locations your study needs, then record exactly where each one lands in the GUI.

How to match a cap plug to a board channel

Read the printed cap label, such as F3, Cz, or O1.

Trace one colored HPTA lead back to its board pin. Example: orange on Cyton N3P is GUI channel 3.

Join the blue HPTA end to the chosen black cap lead until snug.

Write it down: F3 → Cyton N3P → GUI 3. Color helps tracing only.

What does F3 mean?F = frontal region. Odd numbers = left side, even numbers = right side. z = midline. So F3 is a left-frontal cap location.
FP / FFrontopolar / frontal
C / TCentral / temporal
P / OParietal / occipital
ODD / EVEN / ZLeft / right / midline

Interactive channel plan

Pick one cap label per channel. This stays only in this open session; download a CSV if you need a durable record.

04

Fit the cap, reach the scalp, then add gel

The cap goes on before gel. Hair must be separated at every active site so the applicator reaches scalp rather than depositing gel on hair.

Choose the right cap size

It should sit firmly without painful pressure. Confirm the participant has no irritated or broken skin at planned electrode sites.

Orient and center the cap

Use your lab’s 10–20 positioning procedure. Keep left/right correct and prevent twisting as the cable bundle is arranged.

Connect only the positions you need

You have 16 recording channels. REF and GND are reserved. The remaining unused cap positions can stay unplugged.

Part the hair through each opening

Move strands aside with the blunt syringe/applicator so there is a clear path to the scalp.

Inject a small amount at scalp level

Guide the blunt tip through the opening and hair until it reaches the scalp gently, then add only enough gel to bridge scalp and electrode. Never scrape or use a sharp needle.

Route the cable bundle

Give it slack and support its weight. Cable tugging, jaw tension, blinking, facial movement, and head motion create artifacts much larger than EEG.

Dedicated REF. It connects through HPTA to the Y-splitter.
The opening. Part hair here and reach scalp before dispensing gel.
Applicator. Use a blunt tip and gentle pressure.
Conductive gel. Water-based gel improves electrode-to-scalp contact.
More gel is not betterExcess gel can spread between nearby electrodes and electrically bridge them. Start small. If a channel is poor, re-part the hair and check the connector before flooding the site.
05

Power, connect the GUI, and verify the signal

Power comes from the battery on Cyton. Communication comes through the USB dongle. The two physical switches must be in their normal recording positions.

Inspect and charge the battery off-board

Do not charge a swollen, punctured, leaking, or hot LiPo. Use a compatible single-cell LiPo charger and its documented indicator behavior. Keep the board and participant disconnected while charging.

Plug the battery into Cyton

Seat the white JST plug in Cyton’s battery socket without pulling the wires. The USB dongle does not power the board.

Set Cyton to PC

Move the board’s switch to PC—not OFF and not BLE—for USB-dongle communication.

Set the dongle to GPIO 6

Move the dongle’s small switch to GPIO 6, not RESET, then insert it into the laptop.

Open OpenBCI GUI

Select the Cyton workflow, the dongle serial port, and the Cyton + Daisy / 16-channel configuration. Start the session only after the board and dongle LEDs indicate power.

Confirm channel quality

Verify channels 1–16 are present. Use the GUI’s impedance/contact tools according to your protocol. Re-seat connections, re-part hair, or add a small amount of gel where needed.

Run a short functional check

Record eyes open, then eyes closed, then a deliberate blink. Confirm the traces respond and that your file naming, event timing, and channel map are correct.

Download OpenBCI GUISoftware options
Battery. Use the compatible JST plug; do not pull on the wires.
Cyton switch. Recording over the dongle requires PC.
Dongle. Set its switch to GPIO 6, then plug it into the laptop.
Charging station. Charge the LiPo off-board with a compatible single-cell charger; never charge on a participant.

Pre-recording gate

Readiness

0 of 10 checks complete

Not ready to record

What the system can actually measureWith scalp electrodes, it records EEG voltage over time—useful for oscillatory activity and event-related responses when the design and analysis support them. With suitable electrodes and protocol, Cyton channels can also record EMG or ECG. It does not directly read “attention,” “stress,” “trust,” or thoughts; those are constructs that require validated analysis and triangulation.
06

Save, power down, clean, and troubleshoot

Protect the data before disconnecting. Protect the cap by removing gel immediately. Protect the electronics by keeping every adapter and board dry.

Close-down sequence

Stop the stream and confirm the file exists. Note anomalies, channel mapping, filters, and event timing.

Switch Cyton to OFF, then disconnect the participant gently by connector bodies—not by pulling wires.

Immediately soak the cap for about 15 minutes in warm water so remaining gel dissolves. Use a cotton ball on residue if needed.

Rinse thoroughly in clean water; finish with deionized or distilled water if available.

Hang the cap away from sunlight until completely dry. Store only when dry.

Disinfection after cleaningThe supplied guide allows up to 30 minutes in about 100 ppm sodium hypochlorite. With 5.25% household bleach, that is a 1:500 dilution. Rinse thoroughly, finish with deionized/distilled water if available, and dry completely. Follow your institution’s approved infection-control procedure if it differs.
Keep dryTouch-proof plug ends, HPTA connectors, Cyton, Daisy, dongle, battery, and charger. Handle the electrode-to-wire joint gently. Do not leave gel on electrodes or wire.

Troubleshooting

All channels are noisy
Check the shared reference first: both bottom SRB pins must be joined by the Y-splitter and its single end must reach cap REF. Confirm cap GND reaches Cyton BIAS. Reduce participant, cable, chair, jaw, eye, and head movement. Keep mains adapters away from leads.
Only one or two channels are noisy
Trace the affected GUI channel to its board pin and cap label. Re-seat both ends, separate the hair again, and add a small amount of gel. Do not flood the site.
Channels 9–16 are missing
Confirm Daisy is squarely stacked and seated, the GUI is configured for Cyton + Daisy / 16 channels, and Daisy N1P–N8P are connected.
The GUI cannot connect
Check Cyton is on PC, the dongle is on GPIO 6, both LEDs are lit, and the correct serial port is selected. Reinsert the dongle if necessary.
A channel is flat
Check that channel’s header connector, touch-proof cap connection, GUI enable/gain setting, and electrode contact. A flat line is often a disconnected or disabled channel.
A crimp terminal slips from its housing
Power off. Push the metal terminal into the black housing until the locking tab catches. If the tab is flattened, gently lift it; if broken, replace the lead. Do not operate with loose bare conductors touching the board.
Can this be used for sleep or long recordings?
The source guide describes the gel cap as suitable for sleep work and notes that movement still creates artifacts. For an overnight recording, battery capacity, participant comfort, event annotation, and an approved safety protocol must be planned. A high-capacity 2500 mAh battery is cited as an overnight option, but verify runtime for your exact system before a participant session.
Can I record EOG, EMG, or ECG too?
Yes, with suitable electrodes, placement, channel gain, filters, and protocol. Mixed signal types can occupy different CytonDaisy channels. Do not treat cap scalp channels as automatically valid for non-EEG signals.
What files and integrations are available?
The GUI can visualize, filter, stream, and save OpenBCI data; the supplied guide mentions CSV or BDF output and streaming via UDP, OSC, LSL, and Serial to tools such as MATLAB, Python/BrainFlow, and other compatible software. Confirm the current GUI options in the official documentation.

Bench reference

CAP REFHPTA → Y-splitter single end → both bottom SRB pins
CAP GNDHPTA → Cyton bottom BIAS only
GUI 1–8Cyton bottom N1P–N8P → eight chosen cap electrodes
GUI 9–16Daisy bottom N1P–N8P → eight chosen cap electrodes
UNUSEDAGND and AVDD on both boards; Daisy BIAS
CYTON SWITCHPC for dongle communication
DONGLE SWITCHGPIO 6, not RESET
POWERCompatible inspected LiPo connected to Cyton; never charge on participant
Official Daisy getting-started guideOpenBCI downloadsSoftware documentation

This guide combines the supplied OpenBCI instructions with the photographed bench setup and the wiring corrections made during assembly. It is a research setup aid, not a diagnostic or clinical protocol.

Enlarged setup photograph