This module was first described in the original ethoscope paper (Geissmann et al 2017) and used quite extensively after that. We do not recommend using this module for long term sleep deprivation experiments for two reasons:

• the stimulus it can provide is not strong enough to keep flies awake for long periods (>12-24h)
• the motors it uses are not meant to be used with such a high frequency and will eventually fail

Having said this, the module is very easy to build and can be used successfully for short term sleep deprivations or for arousal detection.

Testing the motors

Parts and building procedure

• Only two parts need to be 3D printed for the module. The external chassis (available on onshape here) and the pulley (here).
• You will also need 10 9g servo motors per module. We use this model (RB-Fit-03 from Robotshop). 9g is a common standard for DIY RC plane enthusiasts so you should be able to find these motors from many other sources. Just make sure you do not buy the version that allows for continuous rotation, as that would need different software and would not provide a stimulus that is strong enough.
• The motors can be piloted using a Lynxmotion servo board (RB-Lyn-850 on Robotshop). A bluetooth model exists too but make sure you buy the USB version.
• You will also need nitrile o-rings of 22mm x 1.5 mm to connect the pulleys to the tubes. We used this model but probably any model with the same specs will work.

<aside> ☝🏾 Buy more motors than what you think you need. They will fail quite frequently and you will have to replace them quite often.

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Start the assembly by fitting the pulley into the motor gear. A 9g motor would normally ship with a series of plastic adapters and three small screws. You will have no use of the plastic adapters for this module, but it is convenient to use the tiniest of those screws to secure the pulley to the motor. It is also a good idea to secure the two together with a drop of superglue too, obviously having care of not letting the glue interfere with the mechanism.

Use the remaining two screws to secure the motor in position in the chassis, as shown in the photo below. Note the orientation of the motors. The pulley should face the side where the ethoscope will sit on (i.e. not the fully open side). Optionally, you can use two cable sleeves or 2-3 short zip ties to bundle the 5 wires together and clean the cable mess a bit.

Once all the motors are secured, proceed to connect them to the board using the pairing illustrated with below. The 10 motors need to be connected (in order) to pins 0-9 on the board. The ground of the motors must be connected to the ground on the board (the pin closest to the edge of the board is the ground). The motors' cables have a colour code that indicates ground either in black or brown.