Software and Hardware to Reproduce and Extend our Work
PV-Tiles Toolkit
PV-Tiles is a novel material that closely couples photovoltaic energy harvesting and light-sensing materials with digital interface components.
The concept of PV-Tiles includes three layers - PV layer: organic photovoltaic (OPV) cells, interaction layer and control layer.
These tiles are composed of digital elements—such as displays, sensors and communication—and photovoltaic materials that can be aesthetically layered on the tile,
providing both beauty and the ability to harvest energy to power the digital components.
Here you will find a step-by-step process to reproduce and extend our work. You can download the PV fabrication process, hardware design, and software code to create prototypes such as the ones shown in this video:
Organic photovoltaic (OPV) cells fabrication:
The fabrication process includes cleaning, solution preparation, spin coating, electrodes, encapsulation, and electrode evaporation.
Our self-powered interface consists of an array of 4x4 OPV tiles overlaid on a 4 x 4 array of ultra –low power polymer network liquid crystal displays (LS013B7DH03 by Sharp).
The interface remains in energy harvesting mode when no movement detected by the ultra-low power PIR module.
In this mode the microcontroller is in low power mode, where its current consumption is less than 1 mA @ 3.3 V.
The output from the PIR module is connected to an interrupt enabled input pin on the microcontroller (MSP-EXP430F5529LP).
As soon as the PIR is activated by movement (e.g. a human hand in close proximity to the OPV array), the microcontroller switches to gesture sensing mode.
In this mode photocurrent generated by the OPV tiles is sent, via individual analog switches and two 8:1 analog multiplexers, to a resistor which converts the photocurrent to a voltage drop that can be measured by the microcontroller’s on-chip analog-to-digital converter.
Voltage variations are processed by custom algorithms on the microcontroller.
Text and images written to relevant displays. In order to write to individual displays, a shift register converts serial data from one of the microcontroller’s digital outputs to parallel data that is used to enable one or more displays for writing.
The displays are driven by a separate display driver module (BOOSTXL-SHARP128). A nano-power 1 Hz oscillator is used to switch the displays’ common electrodes in order to prevent charge accumulation and subsequent image ‘burn in’. Below you can download the hardware designs of PV-tiles.
When the PIR sensor detects movement near the device, it is automatically switched to interaction mode. We implemented two modes of PV-based
gesture sensing:
Hover-input with partial tile shadowing, and
Touch-input with full occlusion of the PV area
When the voltage drops below the lower threshold the system assumes a touch gesture has occurred. If
the voltage is below the upper threshold but above the lower, the system actions a hover gesture. As each of the tiles can
independently sense hover gestures, by monitoring dynamic changes across the full prototype we are able to implement
mid-air “swipes”: i.e., a hover gesture moving left, right, up or down across the prototype.
PV-Pix is a slum community co-design of self-powered deformable smart messaging materials for inter-home connections.
Each PV-Pix element consists of a deformable energy harvesting material that, when actuated by a person in one home, changes its physical state both there and in a connected home.
PV-Pix includes two forms of prototypes one uses rigid materials (TiltTile) and the other flexible ones (FabricOn).
By using the following step-by-step process you can build your own PV-Pix or you can reproduce our work. You can download the PV-Pix fabrication guide, electronics,
prototype designs, software code to create prototypes such as the ones shown in this video:
Dye Sensitised Solar Cell (DSSC) fabrication:
The fabrication process includes cleaning, solution preparation, spin coating, electrodes, encapsulation, and electrode evaporation.
Our self-powered interface consists of two hardware devices: TiltTile and FabricOn. Here you will find a step-by-step process of the hardware and electronic design and construction of these devices, and demonstrate their ability to provide self-powered remote
communication.
The TiltTile hardware uses an dye sensitised solar cell (DSSC), the fabricated custom DSSC cells in our laboratory is mounted inside an acrylic inner frame with mitre gears at the top and bearings at the bottom (see TiltTile state diagram (a)) and electrical pressure connectors on the sides, extended beside the
gears. This component fits into a larger frame (see TiltTile state diagram (b)) to create a single TiltTile module. A servo motor is used to rotate each
solar cell around its vertical axis (see TiltTile state diagram (c)), with an MPPT energy harvester/charger board, lithium-ion battery, microcontroller and
XBee wireless communication board for control and remote connection. A discreet, lab-made touch sensor is mounted on the frame to provide interactive input. We built two 2×2 configurations of these
modules to demonstrate the design’s ability to provide remote communication as explored in the low-fidelity prototype study. When an individual TiltTile is touched, it rotates from the closed to open state
(or vice-versa), shortly followed by its remote counterpart.
The FabricOn hardware uses an organic photovoltaic (OPV) cell, and is deformable, designed to be mounted over a curtain. In this demonstrator, then, a FabricOn module changes its state by rolling or unrolling a section of PV tape.
To achieve this we used commerciallyavailable flexible bidirectional solar cells of 110 mm × 160 mm which are mounted on a 3D-printed casing (see FabricOn state diagram (a). The
hollow casing was also used to hide an MPPT board, lithium-ion battery, servo motor, microcontroller and wireless communication board. As with the TiltTile modules, a discreet touch sensitive switch is also mounted on the casing to provide user input.
Below you can download the hardware designs of PV-Pix.
