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The uA2240 programmable timer/counter may be operated by an external clock as shown in Figure 7-44. The internal time-base oscillator is disabled by connecting the trigger input (pin 13) to ground through a 1 kΩ resistor. An external clock is applied to the time-base output (TBO), pin 14. For proper …

Two uA2240 timers may be cascaded to provide long time delays as shown in Figure 7-43. Each uA2240 counter consists of a time-base oscillator, an eight-bit counter, a control flip-flop, and a voltage regulator. The frequency of the time-base oscillator (TBO) is set by the time constant of an external …

The uA2240 may easily be connected to operate as a programmable voltage controlled frequency synthesizer as shown in Figure 7-41. The uA2240 consists of four basic circuit elements: (1) a time-base oscillator, (2) an eight-bit counter, (3) a control flip-flop, and (4) a voltage regulator. The basic frequency of the …

The uA2240 may easily be configured as a programmable voltage controlled timer with a minimum number of external components. The basic programmable timer circuit is shown in Figure 7-39, including the functional clock diagram of the uA2240. Counter outputs Q2 through Q6 are not shown in Figure 7-39. A useful …

This application is a useful addition for the bedroom telephone stand. When the telephone rings, or when the handset is lifted, the night light is turned on and remains on while the conversation takes place. When the handset is replaced in the cradle, the light remains on for about 11 …

The speed of a de motor is proportional to the applied voltage, but the torque diminishes at low voltages. Low speed performance is usually erratic when analog controllers are used, especially under changing load conditions. Pulse-width-modulated (PWM) controllers offer superior control and operate efficiently at low speeds. The PWM controller …

This circuit performs a function that is somewhat different than a frequency-to-voltage converter. The circuit can be more easily analyzed by examining the individual sections as shown in Figure 7-32. Timer U1 operates as a free-running oscillator at 60 Hz, providing trigger pulses to timer U2 which operates in the …

There are many different types of voltage controlled oscillator (VCO) circuits that can use an IC timer. VCO circuits are valuable for instrumentation, electronic music applications, and function generators. The output is a rectangular pulse stream whose frequency is related to the external control voltage. A VCO circuit using the …

The standard 555 ordinarily requires a negative-going trigger pulse to initialize operation; however, a positive-going triggger pulse may be used to start the timing cycle with the circuit shown in Figure 7-29. In this design the trigger input (pin 2) is biased to 6 V (1/2 VDD) by divider R1 …

It is often desirable to have two LEDs turn on and off alternately. Advertising signs frequently use this type of operation. Alternating LED action is easily accomplished using the circuit shown in Figure 7-28 with the TLC555 operating in the astable mode. The timing components are R1, R2, and Ct. …