Products for USB Sensing and Control
Products for USB Sensing and Control
Need a user-friendly control panel for your Phidgets project? Look no further than the Touch Wheel Phidget. This user interface board uses capacitive touch technology, similar to the touchscreen on a smartphone. Capacitive touch sensors such as this can detect a touch through a piece of glass or plastic of up to 3mm thick, so you can hide this board inside an enclosure or behind a panel.
This board has four touch buttons and one fully-functional scroll wheel pad. Whenever a button or the scroll wheel is initially touched, an event is fired in software, allowing you to react immediately to the change. The scroll wheel also generates an event whenever your finger's position changes as you slide it across the wheel. You can also adjust the sensitivity of the board to avoid missed touches or unintentional touches.
| Sensor Properties | |
|---|---|
| Controlled By | VINT |
| Detecting Distance Max | 5 mm |
| Sampling Interval Min | 20 ms/sample |
| Sampling Interval Max | 250 ms/sample |
| Electrical Properties | |
| Current Consumption Min | 20 μA |
| Current Consumption Max | 2 mA |
| Physical Properties | |
| Operating Temperature Min | -40 °C |
| Operating Temperature Max | 85 °C |
| Sensitivity (0-1) | Application |
|---|---|
| 0.8 - 1.0 | Behind up to 3mm of glass |
| 0.2 | Inside default enclosure |
| Channel Name | API | Channel |
|---|---|---|
| Capacitive Touch Sensor | CapacitiveTouch | 0 - 3 |
| Capacitive Scroll Wheel | CapacitiveTouch | 4 |
| API | Language | OS | |
|---|---|---|---|
| CapacitiveTouch | C | Multiple | Download |
| CapacitiveTouch | C# | Windows | Download |
| CapacitiveTouch | Java | Multiple | Download |
| CapacitiveTouch | JavaScript | Any | Download |
| CapacitiveTouch | Objective-C | macOS | Download |
| CapacitiveTouch | Python | Multiple | Download |
| CapacitiveTouch | Visual Basic .NET | Windows | Download |
| Date | Board Revision | Device Version | Comment |
|---|---|---|---|
| August 2017 | 0 | 103 | Product Release |
Next, you will need to connect the pieces:
In order to demonstrate the functionality of the HIN1001, the Phidget Control Panel running on a Windows machine will be used.
The Phidget Control Panel is available for use on both macOS and Windows machines. If you would like to follow along, first take a look at the getting started guide for your operating system:
Linux users can follow the getting started with Linux guide and continue reading here for more information about the HIN1001.
After plugging the HIN1001 into your computer and opening the Phidget Control Panel, you will see something like this:
The Phidget Control Panel will list all connected Phidgets and associated objects, as well as the following information:
The Phidget Control Panel can also be used to test your device. Double-clicking on an object will open an example.
When you double click on a Capacitive Touch object, a window like the one pictured will open.
Unlike most other Phidgets, setting a data interval on the HIN1001 affects its initial response time, rather than an overall data rate. After the first touch has been detected, the device will stream data as fast as possible (up to every 16ms, as data becomes available). This means that if setting a data interval of 250ms, the first touch may need to be held up to 250ms to wake the device, after which subsequent touches on all channels will be detected much faster, until no touch is detected for a few seconds. Once the device has been left alone for a few seconds, it will resume its low-power state and wait for the next touch.
Since capacitive touch sensors rely on checking capacitance against a threshold to detect when they are touched, they need to keep a good baseline of the capacitance of their environment. The HIN1001 will re-calibrate its baseline levels if it detects a constant touch for more than 50 seconds, in order to prevent getting stuck in a touched state. Similarly, it will re-calibrate its baseline capacitance to adjust to falling capacitance (such as when it is moved away from a surface) in order to prevent getting stuck in a not-touched state. The latter adjustment happens as soon as the baseline is detected to have fallen.
Since the touch wheel is circular, calculating the change in position of a finger over the wheel can be more involved than simply subtracting one position from another. In cases where the value crosses the zero point, a simple subtraction would indicate a large movement in the opposite direction. For example a movement from 0.9 to 0.1 would appear as a movement of -0.8, when a movement of +0.2 is much more likely. As such, a change is position should be calculated taking this into account. Here is an example of how to do the calculation in C:
static void CCONV
onTouchHandler(PhidgetCapacitiveTouchHandle ch, void *ctx, double touchValue) {
double change = (touchValue - oldPos);
static double oldPos;
if (change > 0.5)
change -= 1;
else if (change < -0.5)
change += 1;
oldPos = touchValue;
...
}
This Phidget is a smart device that must be controlled by a VINT Hub. For more information about VINT, have a look at the VINT Primer. You can use a Phidget Cable to simply and easily connect the two devices. Here's a list of all of the different VINT Hubs currently available:
| Product | Board | ||
|---|---|---|---|
| Image | Part Number | Price | Number of VINT Ports |
 |
HUB0000_0 | $30.00 | 6 |
Use a Phidget cable to connect this device to the hub. You can solder multiple cables together in order to make even longer Phidget cables, but you should be aware of the effects of having long wires in your system.
