Rodent Operant Bucket

Photo of the ROBucketView full-sized image

The Rodent Operant Bucket (ROBucket), designed by Dr. Alexxai Kravitz and Kavya Devarakonda of the Eating and Addiction Section, Diabetes Endocrinology and Obesity Branch, NIDDK, is an inexpensive and easily assembled open-source operant chamber, based on the Arduino microcontroller platform, that can be used to train mice to response for a reward. The apparatus contains two nose pokes, a drinking well, and a solenoid-controlled sucrose delivery system. The chamber can easily run magazine training, fixed ratio and progressive ratio training schedules, and can be programmed to run more complicated behavioral paradigms.

The ROBucket chamber consists of a 4-quart square plastic container (6.5 in x 6.5 in x 8in) and a simple input-output circuit. The chamber is equipped with three photo interrupter sensors, which serve as nose pokes and a drinking well. When a mouse pokes its nose between the arms of the nose poke, a 5V TTL signal is sent to the Arduino. The Arduino then sends a 5V signal to trigger a solenoid valve through a relay module. The signal causes the solenoid to open for 200 msec, allowing approximately 60 μL of sucrose solution to be dispensed into the drinking well. As each behavioral event occurs, the Arduino logs and displays this information through the SD shield and LCD keypad shield, respectively.

What is an operant conditioning chamber?

Operant boxes reinforce or punish certain behaviors by pairing them with an outcome. For example, a chamber may reinforce nose-poking in mice by delivering sucrose solution each time they poke. More complicated operant paradigms can test reward learning and finer features of motivation, such as increased reinforcement of food directed behavior.

Photo of an operant conditioning chamberView full-sized image

Why make an operant chamber when there are commercially sold and validated options?

Commercially sold operant chambers can cost thousands of dollars per chamber, not including the cost of the corresponding software packages. This cost may prevent researchers from performing important behavioral experiments and makes high-throughput experiments (involving dozens or even hundreds of chambers) financially impractical in most environments.

Furthermore, ROBucket is extremely versatile. The Arduino “sketch”, or program, is easily modified to fit specific experimental needs, and there are an array of widely available Arduino-compatible sensors and shields that can be added on to the operant chamber.

What is Arduino?

Arduino is an open source electronics platform with a fairly simple programming language. The Arduino UNO R3 is a microcontroller board that can receive and transmit input and output signals through 14 digital pins and 6 analog pins. Users can create sketches with the Arduino integrated development environment (IDE) software and upload those sketches to the Arduino board through a USB connection.

To learn more about Arduino, visit

For more information about how Arduino boards can be used in the laboratory setting is available in the following publications:

D’Ausilio, A. (2012) Arduino: A low-cost multipurpose lab equipment. Behavior Research Methods, 44, 305-313. Doi:10.3758/s13428-011-0163-z

Pineño, O. (2013) ArduiPod Box: A low-cost and open-source Skinner box using an iPod Touch and an Arduino microcontroller. Behavior Research Methods. Doi: 10.3758/s13428-013-0367-5

How do you make ROBucket?

Making your own operant chamber is simple if you have a basic familiarity with electronic parts and tools. Our prototype combines the Arduino UNO R3 board with photo interrupter sensors, a secure digital (SD) card shield, a liquid crystal display (LCD) keypad shield, a 2-channel relay module, and a solenoid to build a simple operant conditioning chamber for less than $150.

The Arduino library, RTClib, can be found here:

Files for download

Step-by-step instructions on how to build ROBucket:

Adobe Illustrator ROBucket design files:

ROBucket code:

Adding 3D printing to ROBucket

In addition to the main hardware, a 3D printed plastic housing is combined with a stainless steel three-port Ethernet faceplate to enclose the nose poke and drinking well inside the bucket. The part was designed using the free online software, Tinkercad (Autodesk, Inc., San Rafael, CA), and printed using the Makerbot Replicator 2 Desktop 3D Printer (MakerBot Industries, Brooklyn, NY); any 3D printer may be used. Printing services were provided by the NIH Technology Sandbox.

Files for download

Design file: ROBucket nose poke housing (STL, 92.56 KB)

CAD model:

Photos of ROBucket nose poke housing 3D model and the liquid delivery tubeView full-sized image