The Archimedes project aims at developing a system for investigation of effort based decision making and dexterous motor skills in mice. Archimedes can be used to explore questions in either domain individually but has its strength in the potential for studying the interaction between fine motor skills learning and effort driven flexible decision strategies in mice.

Archimedes control (lever)

The Archimedes system uses a hall sensor to track the whole angular trajectory resulting from the force applied by an animal on a lever (with 14 bit precision and up to 1 KHz sampling rate) coupled to a small linear actuator which would slide a counter-weight beyond the fulcrum, on the hidden side of the lever parallel to its length (and therefore change the amount of force required to execute a press on a trial by trial basis). A single PCB houses both systems (sensor and actuator).

The Archimedes board continuously tracks the lever position and relays this information to a computer through a micro USB port or other boards through a UART connection, by using the Archimedes interface board [HDMI connection].

Key Features

  • Angular trajectory reading with dynamic counter-weight.
  • Angular reading sample rate up to 1 KHz
  • Trigger pre-configured counter-weight positions or LEDs
  • Can be used for Sync purposes
  • Reflects thresholds transitions
  • Output pulses for valves
  • 3x RGB LEDs with intensity regulation
  • 4x Pre-configured thresholds


  • 4x Digital inputs
  • 5x Digital outputs
  • 1x Analog input


  • Animal behavior with levers

Archimedes interface

Interface for the Archimedes control (lever) device. Connection is made using the HDMI port.

This board supports USB or Serial (UART) communication and can be used to control the Archimedes board or output data from it.


  • 1x clock sync input (CLKIN) [stereo jack]
  • 1x USB (for computer) [USB type B]
  • 1x 5V supply [barrel connector jack]
  • 1x HDMI
  • 1x serial port (UART) [RJ45]
  • 1x Gen port [RJ45]
  • 1x ADC [screw terminal]
  • 4x digital input: IN0 [BNC], IN1-IN3 [screw terminl]
  • 6x digital output: OUT0 [BNC], OUT1-OUT5 [screw terminal]

SW configuration options

  • Thresholds and sample rate
  • LEDs: 7 preset configurations - LED position and RGB values
  • Digital inputs and outputs: assign different actions, and define pulse interval (OUT4 and OUT5)
  • Attribute preset LED configurations to thresholds transitions
  • Attribute preset counter-weight positions (motor steps)
  • Event firing on: thresholds, lever angular position & analog input, inputs when a transition is detected, current position of the counter-weight

SW download and screenshots

Harp Archimedes

Thresholds & Sample Rate