Building Small Efficient and Econologic Resistors or rack of resistors in the range of a few Ohms to MegaOhms can easilly be done using ElecroFunctionnal Paper 1K or 100K.
Follow these Steps to know-how and build your first eco-friendly resistor.
1- Design the Force sensing Resistor
1.1- Design the Force sensing Area
PLK Fabrication Kits enable the production of any force sensitive shape that you can cut into the conductive paper sheets.
Draw you design onto the design cardboard and add (or include) a few mm borders area.
1.2- Design the Metal Circuit and connectors location
Small and simple designs such as round or square areas can be very quickly designed here: the goal is to o connect both paper electrodes using wires and/or metal tape and build a connection tail for this 2 poles component.
Larger and more complex designs such as large sensing tiles, long sensors or else sensors with complex shapes can profit finer circuits designs so as to provide more uniform responses along the surface.
Draw the location of your connectors or connecting tail aside from the sensitive surface.
2- Build up Electrodes and Barrier Sheets
2.1- Cut Resistive Barrier layer
PLK fabrication Kits provide high volume resistive sheets of the order of 100 kΩ/Sq to be used here as a piezoresistive barrier. It must be placed between electrodes sheets so as to prevent direct contact between the electrodes. It provides uniform response over the surface when used with electrodes sheet. For sensors of the size of the thumb or below, this layer can be replaced by an insulating spacer made of simple cardboard.
Use your design to cut a piece of resistive sheet of the size of the sensitive area.
2.2- Cut the Electrodes Layers
PLK fabrication Kits provide low volume resistive sheets of the order of 1kΩ/Sq to be used here as Electrodes layers when used with a high resistive barrier. It must sandwich the resistive barrier so as to prevent direct contact between each other.
Use your design to cut 2 pieces of Electrode sheets of the size of the sensitive area.
2.3- Design the metal circuits over the Electrodes Layers
PLK fabrication Kits provide tin-plated copper tape with conductive adhesive to generate connectors onto the electrodes sheet and generate thin internal circuits towards thee components connectors. The larger or complex the sensor the more refined metal connector will be required over the Electrodes. The tape has a width of 0.6 mm which is great for the pads locations. It can easily be narrowed int 2 or three bands of a few mm especially for small sensors.
Select the most appropriate circuit design from the examples provided here. and draw this design onto your cardboard model linking each electrodes papers to a connection pad. .
Cut one piece of the desired size of your sensors from a few mm to meters. A A5 sheet enables for instance to cut 3 * 4 pieces of 4.8 cm * 5.2 cm which corresponds roughly to An Interlink FSR406 or a Tekscan Flexiforce A502.
PLK fabrication Kits provide volume resistive sheets of the order of 100 kΩ/Sq to be used here as a piezoresistive barrier to build FSRs ranging from above 100kΩ down to a few kOhms depending on the size and the force applied. It must be placed between electrodes sheets so as to prevent direct contact between the electrodes. Cut one piece of the desired size of your sensors from a few mm to meters. A A5 sheet enables for instance to cut 3 * 4 pieces of 4.8 cm * 5.2 cm which corresponds roughly to An Interlink FSR406 or a Tekscan Flexiforce A502.
PLK Kits also provide volume resistive sheets of the order of 1 kΩ/Sq to be used here as a Sensing Electrodes. These twin pieces will define the size and shape of you sensitive area. The 2 A5 sheet enables for instance to cut twice 3 * 4 pieces of 4.6 cm * 5 cm, so as to collect 2 pieces for each of the 12 sensors. Note that these pieces are slightly smaller that the piece of resistive barrier to ensure no contact when assembled.
An insulating support and cover is not compulsory but can be useful for many reasons: - to enhance the sensor's rigidity and solidity to shear and small impacts. - to enhance the sensor's resistance range and maximise the default resistance value. - to adapt the influence of the surface contact and the load input sensity. - to provide a support extension for the connectors.
Small sensors of a few inches square such as the ones produced here may simply require a thin spacer made with a classic writing paper and a cutter. The bigger the sensor, the thicker should be the spacer with more refined designs.
Connectors can be made using the metal tape with conductive adhesive. The tape provided in the Kits is 0.6cm width and can easilly be cut into bands of 0.2 to 0.3 cm width especially for small sensors.