Wednesday , September 18 2019

uA2240 Operation With External Clock Design

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 …

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Cascaded Timers For Long Time Delays

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 …

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Programmable Voltage Controlled Timer Design Using uA2240

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 …

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PWM Motor Controller Design Using TLC555

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 …

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Capacitance To Voltage Meter Design Using TLC271

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 …

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Voltage Controlled Oscillator Design Using TLC555

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 …

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Positive Triggered Monostable Using NE555

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 …

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Alternating Led Flasher Using TLC555

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. …

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