Test your productions

An Ohmmeter will help to produce and specify your sensors

New productions and prototyping can only be successful if you constantly test your materials, design and productions using appropriate tools and depending on your objectives.

Learn here how to quickly test you productions with a battery and a led but also more interestingly how to test them with a multimeter and how to use microcontroller to acquire related signals.

Circuit Test

When building resistors wand small circuit components with Papier Logik resources, a power source and a led may be enough to test shortcut and relative voltage outputs when resistance values are not too high (below the kOhms order).

This can already lead to a lot of fun and educational applications with little resources but when developing higher levels components such as more complex circuits or sensors, an Ohmmeter or equivalent digital tools should become you friends sooner or later. Here is a collection of good practices and useful information related to securely buildng, testing and specifying you sensors.

Testing with an Ohmmeter

A multimeter is the best tool for detecting shortcuts and measuring conductive materials and resistive sensors. Set as an ohmmeter,

Be aware that you will not read the same value for a component if you test it on the side or if you test it inside a powered circuit.

Testing with an Arduino

An Arduino is the best way to test and use resistive-based sensors, but also to build low-cost oscilloscopes to test materials and used them to build components.

With sufficient output range (e.g. 1k to 100kOms) a Voltage divider makes a simple electronic circuit to plug a resisitve-based sensors. but other techniques can also be of interest.

Then a development with a micro-controller that can be plugged to a computer or another peripheral like an arduino is a great start for building you first Human Interface Device with a variety of applications and efficiency.

Sensors Signals Aquisition

Papier Logik sensors are most often used with a development board such as an Arduino.

This powerful and low-cost electronics enables to easily connect your sensors and read related signal on a computer using simple components, serial USB communication (r other wireless systems and protocols) and open source programming and data display environments.

We have collected here basic information to connect and get relevant signals data feedback for each type of the sensors we can produce.

Startup Arduino Program

Arduino boards can quickly be programmed to acquire sensors signals and send data to a computer or another peripheral.

Arduino programs uses dedicated libraries based on C++. Most programs make use of at least a setup function that is launched at startup and a loop function that... loops as long as the board is powered.

Minimalist program to manage a sensor signal

So a minimalist program to declare a signal variable, read and store its value in real-time and display signal through serial will work on any Arduino or other board using the Arduino language and would look like this:

#define BAUDRATE 9600

int SensorValue;

void setup() {
  // initialize serial communication at 9600 bits per second:
  Serial.begin(BAUDRATE);
}

// the loop routine runs over and over again forever:
void loop() {
  SensorValue= analogRead(A0);    // read the input on analog pin 0:
  Serial.println(SensorValue);    // print out the value you read:
  delay(1);        // delay in between reads for stability
}

After optionally defining useful global constant and variables, the setup() function enables to setup the Serial communication. The Serial Library is directly available to enable to send data over Serial Communication protocols and ports. The Baudrate setup a size of bits that are (can be) sent per second. 9600 bps is enough for now.

Next. the loop() function is continuously running and it is used here to read and store the sensor value and then to send this value through Serial so that it ca be displayed.

Note: the last line is a delay() function that is good to set low but at least 1ms for better program stability and efficiency.

Voltage divider

The value read using the AnalogRead() function is a 10Bits Value corresponding to the real-time Voltage of the Read Pin (A0). While Papier Logik are variable resistors whose resistance varies significantly for touch sensors design, the sensor must be connected in combination with a fixed resistor between the Vin and Ground Pins so as to divides the voltage at the Analog Pin read.

The circuit and formula below describes how to connect a resistive force sensor so as to read an increasing value with the load applied.

Voltage Divider

The value of Rd depends on your sensor resistance range. Any Rd value in between this range will enable to output s signal, but the lineairty and resolution of this signal depnds on the choice of Rd. The illustration below provides a link to an excel sheet that enables to cLCULte an optimal Rd value.

Test your productions

Circuit Test

Testing with an Ohmmeter

Testing with an Arduino

Startup Arduino Program

Voltage divider

Sensor Type VS Connection to Boards

Connecting Force or Flexion sensors

Sensor Type VS Signal Aquisition, type and display

Display Modes: serial Monitor vs Serial Graph

Physical Calibration

PLK-Arduino Library

PLK-Processing GUI