flyGym
Automated Exercise Device for Drosophila
The flyGym is a motorised 32-vial drum that exercises flies by turning their vials over. Each half rotation drops the flies to the bottom of the vial and they climb back up — negative geotaxis, on a schedule you program. Everything runs from a standalone controller with an OLED display and a knob, with protocols stored on an SD card. No computer required.
Key Features
32 vials at a time
Four 3D-printed shelves of eight standard Drosophila vials, held by printed tube locks on a drum that turns as one. The whole cohort gets exactly the same exercise.
Exercise by negative geotaxis
Every rotation is a half turn that inverts the vials. The flies drop to what is now the bottom and climb back up. No air puffs, no shaking, no handling.
Programs, stages and cycles
Build a protocol from up to ten stages. Each stage sets how many minutes the drum turns, how many minutes it rests, how many turns per minute, and how many turn/rest cycles to repeat — so ramps and interval training are straightforward.
Runs without a computer
The controller is a standalone unit with an OLED, a knob and a button. Programs, configuration and run state are stored on a micro SD card, and the display shows the stage, cycle, rotation count and estimated time remaining.
Closed-loop motion with homing
A closed-loop stepper with encoder feedback drives the drum through a GT2 belt, and an inductive sensor homes the drum to a repeatable start position at power-up and after any configuration change.
Resumable long runs
Training state is written to the SD card as the run proceeds, so an interrupted experiment comes back paused at the right point rather than starting over.
Fully documented design
Supplied with dimensioned engineering drawings, a complete bill of materials and a step-by-step assembly guide, so the instrument can be serviced, extended or rebuilt in your own workshop.
Optional infrared readout
The flyGym Tracker adds an 850 nm back-light and a single camera to score per-vial activity over hours to days, alongside a log of every rotation stimulus. It is in active development.
Technical Specifications
| Capacity | 32 standard Drosophila vials — 4 printed shelves of 8, on a rotating drum |
| Exercise mechanism | Each rotation is a half turn (180 deg), inverting the vials; flies fall and climb back up (negative geotaxis) |
| Drive | Closed-loop NEMA 17 stepper with encoder feedback, GT2 belt to an 80-tooth pulley on the drum axle (4:1 reduction) |
| Protocol structure | Up to 10 stored programs, each up to 10 stages; a stage sets turn time, rest time, turns per minute and number of cycles |
| Rotation rate | Up to 30 turns per minute (factory limit MAX_ROT_PER_MIN); up to 60 turn/rest cycles per stage (MAX_CYCLES) |
| Motion settings | Speed and acceleration adjustable on the device (defaults 15,000 steps/s and 25,000 steps/s2); saved to CONFIG.TXT on the SD card |
| Start position | Inductive homing sensor plus a two-stage homing cycle with fine adjust, so the drum starts from the same position every run |
| Control | Standalone controller: 1.12" 128x128 OLED, rotary encoder, button, micro SD card. No PC or software needed |
| Run length | Programs run and are timed in days, hours, minutes and seconds; state is written to the SD card so a run survives a power interruption |
| Structure | 2020 aluminium profile frame with brushed aluminium side panels, 8 mm stainless axle on 608 bearings, 3D-printed vial shelves with tube locks |
| Footprint | 415 x 235 mm, 272 mm high (505.4 mm overall including the motor) — fits on a bench |
| Power | 24 VDC, 60 W desktop supply |
| Optional readout | flyGym Tracker — infrared per-vial activity index (in active development) |
See the flyGym in Action
Recorded through the tracker's infrared camera during a running protocol.
The flyGym drum turning, seen by the tracker camera
Infrared silhouette view of one drum face — 16 of the 32 vials, in two rows of 8, each holding a group of flies. Two rotation events are visible in the clip: the drum flips the vials, the flies fall, and they climb again.
flyGym Tracker
Optional · in active developmentThe exercise device runs perfectly well on its own. The flyGym Tracker is the optional readout that turns it into a measurement instrument: the drum is back-lit at 850 nm behind a visible-cut filter and imaged by a single monochrome camera, so the flies appear as dark silhouettes against glowing vials — invisible to the flies, and equally usable in the dark phase of the light cycle.
The software measures a per-vial activity index: it detects when the drum is turning and when it is standing still, and only during the stationary dwells does it difference successive frames within each vial's region of interest and count the pixels that changed. That is the same approach used by pySolo-Video and ethoscope — it reports how much a group of flies is moving, rather than tracking individual animals.
Output is a tidy per-vial, per-time-bin table in CSV or Excel, plus an events log of every rotation, so exercise stimuli and activity sit on the same timeline. Runs are designed for hours to days; only the activity table and the event log are stored, not the video.
Related Applications
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