Adding a single zone FSR (Force Sensitive Resistor) sensor is pretty simple thanks to the Snowboard's onboard force touch controller. This force touch controller is able to handle up to 160 single zone FSR sensors simultaneously with total scanning time less than 20 ms (120 us for each single sensor). This onboard controller always scan 160 sensing points when requested. However, in some case, you just want to use one or two FSRs and very fast response from them.
The easiest way to achieve this is to combine the Arduino and reference resistors in the Snowboard.
Let's first start with an example. Wire your FSR and the Snowboard as shown below.
It is convenient to use a small breadboard to implement the wiring above.
Then, upload the following code to the Snowboard.
Run Serial Monitor from Arduino IDE. Squeeze the FSR sensor. You can see that FSR reading is changed according the applied pressure. Speed of reading a single zone FSR sensor is at most 120 us which is quite fast enough for most applications (such as musical instrument).
Now we are in a position to know how it works. On the Snowboard, there are An pins which is part of Snowboard's connectors for force matrix sensors.
These pins are connected to 10 kOhm reference resistor as shown below.
According to the wiring above, an equivalent circuit is constructed as follows. D8 drives the whole circuit by applying 5V. Due to the serial connection of FSR and the 10 kOhm reference resistor, the applied +5V is divided across the two resistors, i.e. FSR and R1. The voltage acroos R1 is measured by A0 (analog input) pin of Snowboard whose value is
A0 (V) = 5 * R1 / (R_FSR + R1)
where R_FSR is the resistane of FSR sensor. It should be noted that this value is decresed according to the applied pressusre. When this voltage is measured by A0 (analog pin), this value is digitized between 0 and 1024. 0 and 1024 correspond to 0V and +5V, respectively.
Since there are six analog pins on the Snowboard, you can attach 6 FSR sensors with this approach. If you need to attach more FSR sensors, then use this method.
We had a question from our customers if the Snowboard can be used with a single zone FSR (force sensing resistor) sensor. An answer was given in our last blog post and today we will go further with this issue.
Shortly speaking, the Snowboard can work with upto 160 single zone FSR sensors. All you need to do is to connect two ends of a sensor to appropriate pins of the Snowboard - One end to D pin and the other to A pin. D pins and A pins are configured as shown in the picture below:
In this post, we will add 3 single zone FSR sensors to the Snowboard.
Add them, upload a firmware and run a visualization application according to this instruction. Press each sensor and you can see the visual response of each sensor.
When you touch all of these sensors, the Snowboard can measure their responses simultaneously.
Did we tell you that an FSR matrix array sensor is technically a large combination of single zone FSR sensors? Yes it's true as each cross point of a row and a column in a matrix array sensor is actually a single zone FSR.
So, what does it mean? The answer is that you can add a single zone FSR sensor to Snowboard! Just pick up any single zone FSR and connect two ends of the sensor to D6 and A0 pins of Snowboard.
Connect the sensor, upload snowforce firmware, and launch snowforce processing application. That's all.
This week we've added a handy sample program that checks the speed of force sensing module of Snowborad.
Here's how to do it.
First, download the latest Snowboard Arduino library and installs it by consulting this link.
Choose File-Examples-forcespeed to open the sample program.
Upload the program.
Choose Tools-Serial Monitor to open Arduino's embedded serial terminal.
The serial monitor will open. Snowboard continuously reads 100 frames and outputs speed information as shown below.
We are currently experimenting with different force matrix sensor arrays to improve the performance and usability of Snowboard. Here are our demo videos. Enjoy!