Many appliances such as information personal digital assistants (PDAs) and instrumentation and control applications are use touch-screen interfaces. This is a application notes of using resistive touch screens for human/machine interface. This application notes describes about how to convert the analog inputs into usable digital data, the basics of how resistive touch screens work, resistive touch screens, resistive touch-screen controllers, and touch-screen acquisition flowchart.
This application note is divided into sections as follows :
-Introduction
-Resistive touch screens
-Resistive touch-screen controllers
-Single-ended configuration
-Differential configuration
-Touch-screen settling time
-Difference between single-ended and differential modes
-Touch-screen acquisition flowchart
-Data-averaging algorithm
Download/view the application note.
The signal-processing block of thermocouple is sensitive to EMI, just like other low-level circuitry. It’s wires are often exposed to EMI. It will increase undermines the accuracy of the acquired temperature data and uncertainty in the received signal. To solve this problem, usually we use special thermocouple cable but it will expensive and if we replace with another cable, the resulting situation will be difficult to diagnose. Therefor, we can use digital transmission to solve the problem. Here is the circuit :
The circuit will minimize noise by moving the controlling circuitry and adding a remote board with local intelligence near the sensing point. A local pulse-sequence generator (IC3 and IC2) drives the MAX6675/MAX6674′s SPI interface. Four characters per second: 1 stop bit, 1 start bit, and 11 data bits (13 data bits for the MAX6675) and a train of asynchronous serial characters at 4800 bauds are generated by the MAX6674/MAX6675 that is forced by IC2 and IC3.
The 11 data bits for the MAX6674 are 1 bit to warn of an open thermocouple and 10 straight-binary data bits for temperature (MSB first). 12 data bits and 1 bit are provided by the MAX6675 for the alarm. [Source: maxim-ic.com]
To protect the loud speaker from destructive signal, the most simple way is by placing a fast blown fuse between speaker and the amplifier output. This common solution is depicted in the figure 1 (a).
Figure 1. Fuse Placement to Preserve Good Bass Response
The fuse in the circuit has a significant resistance to generate heat, because without this the fuse couldn’t melt. The resistance affect the amplifier response in reacting to the speaker inductive load, but the worst is that this resistance varies with the temperature caused by the dynamic signal current. This resistance variation affect the linearity of the amplifier’s bass response. This situation can be solved by placing the fuse inside the amplifier’s feedback loop. Using this method, any nonlinear effect introduced by the fuse will be compensated by the amplifier via feedback mechanism. The resistor R3 is chosen to be much smaller compared to R2 but much higher compared speaker’s impedance. A value of 220? is suitable for most cases.
The idea that a half lie is much more dangerous than 100% lie is implemented in this design. Rather than showing off that our car is 100% protected by a sophisticated alarm and protection system, this anti burglar protection circuit prefer to lie that the car is not protected by any electronic alarm or any protection system. The circuit presented here is based on unusual method to protect car theft. Need not a long time to wait after the machine is started, some troubles will arise. Restarting the machine will produce a same trouble, even worst.
The circuit is very simple. A 555 timer provide a time delay about five seconds. A normally-closed relay is connected between ignition switch and the ignition coil. S1 switch that is used to activate this protection system should be placed in a hidden area. When the ignition switch is turned on to start the machine, the current will flow normally to the ignition system via the relay and the machine will start to work. After a time delay set by the 555 timer ( the time delay can be varied by selecting different value for R1 and C1) , the relay will be open, and the ignition coil will be disconnected, the machine will show something wrong by stop working. You’ll guess that the burglar will try for two or three more try before giving up.
