The information here describes the first generation StimTracker, which is now discontinued. Please see this blog post for information on the new and much improved StimTracker. Information on the new StimTracker will be available here on September 8.

Cedrus Light Sensor

The Cedrus Light Sensor is available in two colors: black and white. Notches are molded in on three sides to allow for easy positioning on the screen.



Response time (dark to light):

Release time (light to dark):

Spectral sensitivity:

0.05 milliseconds

4 milliseconds

360-970 nm (visible light)

The response and release times are dependent on the amount of light.

The Cedrus light sensor is small, measuring a mere 8mm (W) by 20mm (L) including the wire’s strain relief (8 by 14mm without it).


External Input Latencies

USB Port Latency

For best performance, none of the external input sources are routed via the microprocessor. The delays between input and output are:

Light sensors:

Less than 0.01 milliseconds

This is the latency due to StimTracker and does not include the light sensor’s response time.

Voice key:

Less than 0.05 milliseconds after voice level rises above threshold


Onset is less than 0.05 milliseconds after voice level rises above threshold; typical offset values are 50-100ms depending on threshold value

The latency for sending an event code depends on the baud rate selected through the driver. At the recommended 115,000 baud rate, the three byte command needed for sending an event marker takes 0.36 milliseconds to transfer.

Once received, StimTracker processes the command and produces the output in less than 0.1 milliseconds.

There may be additional latencies introduced by the host computer, operation system, application, or a combination of the above, over which StimTracker has no control.

Digital input:

Less than 0.01 milliseconds

Output Currents

The standard output currents are <1mA per-pin for Parallel Port connector (top DB25), and 5mA for the Extra Port connector (bottom DB25).

Pins 2, 14, or 15 on the Extra Port connector provide a 5V output that you can draw up to 250mA from.

On the StimTracker for Tobii TX300 model, the coax connector can source 160mA when it’s high and sink 200mA when it’s low.

On the StimTracker for SMI or ASL models, the mini-DIN connector can supply 5mA per pin.

What’s Inside

A StimTracker order ships with the following:

Product Dimensions:

StimTracker unit

One white light sensor

One black light sensor

A USB cable

An audio cable

A universal AC adapter (100-240V)

5 extra double-sided adhesives for the light sensors





17.8 cm (7 in)

5.6 cm (2.2 in)

13.4 cm (5.25 in)

0.52 kg (1.1 lb)


Related Products

Stay in Touch

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Stimulus Presentation

Response Pads for fMRI

Voice Key

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