Timer Circuits

I had a Basic Stamp project that needed to measure a nominal 12 volt battery, and I wanted a simple solution. This is the simplest I could come up with. The 555 timer will put out positive pulses. The pulse width is inversely proportional to the difference in voltage between the voltage at "ANALOG IN" and the voltage of the 4.7uF capacitor(let`s say 2.5 volts). To calibrate this circuit, hook it up to a Basic Stamp measuring positive pulses, and give the circuit a known voltage...

This application note uses a timer IC (ICL7555), CMOS logic and discrete transistors to automatically control the conversion the MAX190 12-bit SAR analog-to-digital converter (ADC). The delay between conversions can be programed using a resistor. Logic circuits ensures proper startup when power is applied...

Most A/D-conversion techniques use dedicated hardware, usually a single-chip IC. The flexible conversion technique allows you to use successive-approximation, ramp-type, or other converters by writing the appropriate control software. The design in Figure 1 uses a PC`s parallel port for interface to a DAC and a special BIOS interrupt (INT 1CH) for the conversion process. The INT CH hardware interrupt is available in all PCs. It automatically occurs 18.2 times per second; the BIOS-timer interrupt invokes the interrupt after the interrupt updates the time-of-day count...

The position encoder in Figure 1 is a simple yet powerful circuit that converts the change in resistance of a potentiometer into a digital value without using an expensive A/D converter. The working principle is a resistance-to-PWM converter built around the common 555 timer IC. A change in the potentiometer`s resistance causes a proportional change in the duty cycle of the timer`s output, which essentially encodes the resistance values as a PWM signal...