Privacy policy and cookies - INCBTech uses cookies and similar technologies to help deliver the best experience on our site. Our cookies are necessary for the operation of the website, monitoring site performance and to deliver relevant content. You can visit our Privacy Centre to learn more about your online settings.

Search

Rotation Detection Using the MSP430 from Texas Instruments (MIC009E)

Application Report SLAA222A, which can be accessed from the company website, describes the rotation detection with the MSP430 scanning interface. In this application an LC sensor is used for the Scanning Interface of the devices of the MSP430FW42x family. The download address for the document is www.ti.com/lit/zip/slaa222. In this article we summarize what is in this application thus giving an idea for the reader of what is possible to implement with this technology.

Note: Although the article is not current, it can be implemented with newer versions of MSP430.

 

The Operation principle

The idea is to use a non-contact sensing system through an LC circuit (coil and capacitor) as shown in Figure 1.

 

Figure 1 - The principle of the operation.
Figure 1 - The principle of the operation.

 

 

The same system can also be used in detecting the flow of fluids, such as meters of water flow, heat, etc.

In the case of a flow meter, the flow is converted into a rotational movement which can then be measured by the suggested technique.

We position the coil of an LC resonant circuit near a rotating plate, as shown in the figure. Half of the plate is covered with a metal plate such as copper, for example.

This way the damping factor of the resonant circuit will depend on the proximity of the coil to the plate. This damping factor is precisely the magnitude detected by the circuit that serves as a parameter for the measurement to be performed.

With the use of a second sensor it is also possible to detect the direction of the rotation.

In Figure 2 we show what occurs with the damping of the LC circuits during the movement of the rotor used in the sensing.

 

 

 

Figure 2 - As the damping factor is affected by the metallized part of the rotary sensor.
Figure 2 - As the damping factor is affected by the metallized part of the rotary sensor.

 

 

Once the signals from the two sensors are scanned, it is possible to perform the measurement. See in Figure 3 how these signals can be scanned.

 

 

 

Figure 3 - The digitized signals
Figure 3 - The digitized signals

 

 

The complete circuit of the system is then shown in Figure 4, using one of the microcontrollers from the MSP430 family by Texas Instruments.

 

Figure 4 - Complete circuit for rotation sensing with the MSP430.
Figure 4 - Complete circuit for rotation sensing with the MSP430.

 

 

In the Application Report of Texas Instruments, readers will find details about the values of the components used and the performance achieved for the circuit.

Information can also be obtained on Texas Instruments www.ti.com