Dog treat dispenser for assistance dog training
The charity ‘Dogs For Good’ asked us to design and build a bespoke and automated dog treat dispenser for a person living in Devon. The person was on the waiting list to receive an assistance dog, but to commence the training programme she needed to be able to give the dog frequent single ‘kibble’ treats to reinforce the right actions. This person is able to raise and lower one hand but has no grip or manual dexterity.
The Challenge
Our volunteer Paul took up this challenge and after meeting with the charity and the person, they agreed that what was needed was an automated dispenser: To dispense kibbles one by one. To hold 3 oz (85g). To dispense kibbles varying in weight from 0.6g to 2g each (140 to 42 number per 85g). To be sited on the floor or a desk. To be operable by a button on a wheelchair arm.
The solution
After experiment, I chose a round container, tapered at the bottom at 45º, from which a central lifter rises with a cup at the top of diameter suited to the kibble. At the top of the lift an arm rotates so as to flip the kibble down a shute, to the dog.
The lift is operated by a stepper motor (Nema 17) driving a toothed belt, on which is also mounted a projection to move a small nudger inside the container (to discourage the kibbles from forming a stable ring above the bottom of the funnel). At the bottom of the lift stroke is a microswitch to provide a reference position.
The flipper arm is operated by a smaller stepper motor (28BYJ-48), also with a reference position microswitch.
A laser diode shines a beam up through the lift to a light sensor mounted above the flipper arm to detect the presence of a kibble in the cup.
To control these components is an Arduino (compatible) Nano microcontroller, two stepper motor drivers, a 433 MHz radio receiver and a 12–5v buck converter on a bit of vero board.
Power is supplied by a 12v PSU The mechanism and controller are enclosed in a wooden box with a perspex top, on which is mounted a lid to access the container for re-filling, two indicator LEDs, a button switch, a power switch and an alternative diameter cup. The lid operates a microswitch when closed, and is held shut with a magnet.
In use, on being powered, the flipper arm is moved to the ready position, the lift moves first to the bottom, then to about 1/3 of the way up, when the presence of a kibble in the cup is sensed with the vertical light beam. If there is no kibble present, it tries again – if successful it rises to the top and awaits a signal from the remote button – when this is pressed the flipper pushes the kibble down the shute, and the whole routine is repeated.
If the lift fails to find a kibble 4 times in a row, it assumes it is empty, lowers the lift, stops, and the empty LED flashes. While in this state the Slow lift button can be pressed to bring the lift to the top to allow for a change of cup (if changing the size of kibble). Otherwise, the lid is opened for a refill, and on being closed it starts from the beginning. The circuit diagram and software script are available on request
The benefit
The process for life-changing assistance dog allocation can now begin. The charity are already aware of other people around the country who have applied for assistance dogs and would benefit from this device and they will be contacting REMAP about sharing the design and information with other panels. Paul is very happy to share his designs and process.
Paul has also designed and built a portable version for when out and about.
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