BitShifters – Prototype II Final Report: Shelf Assist

Introduction:

The apartments at the Cerebral Palsy Research Foundation (CPRF) provide shelves and cabinets that are not easily accessible to many of the residents, who are confined to wheelchairs. A device is needed to lower the items in these cabinets and shelves to a reachable distance for wheelchair occupants. Manual pull-down shelves already exist on the market, however they are not sufficient. With these pull-down shelves, the residents would still have to reach and pull down the shelf from their cabinets. Since many of the residents have limited use of their hands, an automated pull-down shelf is needed.

Prototype II extends upon Prototype I, which consisted of a manual pull-down shelf without any modifications. For the second prototype, the shelf is motorized using a linear actuator. An Arduino Uno is used to allow the user to control the linear actuator via a dual rocker switch.

The modified shelf consists of the following parts:

  • A generic manual pull-down shelf
  • A 24v linear actuator
  • Nuts, bolts, washers
  • Aluminum supports
  • A fabricated metal plate
  • An arduino uno with motor shield
  • Dual rocker switch
  • A 12v, 3Amp power adapter

Description:

The manual pull-down shelf we chose to modify was purchased from Menards.

http://www.menards.com/main/see-more/home-accessibility/kitchen-laundry-accessibility/cabinet-organization/24-wide-pull-down-shelf/p-1297699-c-9352.htm

Each of the two sides of the shelf consisted of a gas-assist mechanism and two springs. On one side of the shelf (we’ll call it the “motor side”) both springs and the gas-assist mechanism were removed. On the other side (the “stability side”) we kept the gas-assist mechanism and the bottom spring in place, but the top spring was removed.

“Stability side” view of shelf

The linear actuator, which we got from Tom, only extends 4 inches. However, it needed to fully lower the shelf, and it had to be positioned away from the pivot point of the shelf. To achieve this, we fabricated a metal plate that would raise the actuator above the arm and the pivot point of the shelf.

“Motor side” view of shelf

When weight was added to the shelf, we noticed that the actuator was bending the bolt instead of raising the shelf. So, we cut an aluminum support out of scrap metal to go around the bolt.

Aluminum Support

We used an Arduino Uno with a motor shield and a dual rocker switch. When one on the two buttons on the switch is pressed, the Arduino supplies a positive voltage to extend the actuator and lower the shelf. When the other button is pressed, the Arduino supplies a negative voltage which retracts the actuator and raises the shelf. Power is supplied by a 12V, 3Amp power adaptor.

Arduino

Arduino Code

Diagrams:

The diagram above shows the basics of how the shelf operates, how it is controlled, and how it is powered.

Reflection:

Overall, we achieved our goal for Prototype II. We were able to attach the actuator to the shelf, and the fabricated metal plate allows it to fully lower and raise the shelf. Also, we managed to setup the Arduino so that we could control the actuator with a switch. However, there are places that could be modified next semester. For instance, when weight is added to the shelf, it dramatically reduces the speed at which the actuator can lift the shelf. We need to find a way to supply more power to the actuator without frying the Arduino. Also for next semester, we ought to consider the utility of the shelf. How beneficial would our current shelf be for wheelchair occupants, and how can we make it more beneficial?