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35 Threads found on edaboard.com: Timer Comparator
First, you couple and limit the AC waveform (or replica) to a comparator that will flip when the input crosses zero. Then you count (or integrate-and-dump) time pulses until the next one. 1mS timer is going to be coarse even at 50/60Hz (20/17.7mS). Is 4-bit resolution good for anything? Then you do the 1/N math to get frequency from period (N).
Apparently a comparator with an adjustable threshold. The signal from uC could be some output configured as a timer/PWM.
You need to add a comparator IC that has a high input impedance to sense the capacitor voltage without loading it down. The output of the comparator can have 4mA as base current to turn on the transistor that drives a relay that needs up to 40mA. Or use a 555 timer IC to replace your entire circuit.
You can make use of comparator IC like LM339 for doing so. You can use 555 timer for 5 mins. If you need more help let us know
it C4, C5 or both which control the time delay to ON the transistor? Why R4 (3.9M)? thank you very much
if you are a newbie then start learning ne555 based timer. like astable m.v , led flasher. lm324 based comparator. transistor based amplifier. e.t.c look for some old junkie radio, & tv sets. try to understand the components .. study the datasheet & servicemanual
Hello, The HV9803 LED driver says that it avoids subharmonic oscillation. The datasheet says that subharmonic oscillation is avoided by inserting small time delays after the current sense comparator has tripped (as explained on page 5 under "Current sense comparator and timer circuits") But surely this is incorrect, the avoidance (...)
use 555 timer that can do that
now, i'm designing an ir receiver. i want to cut the burst pulse after comparator output, as the picture shows. VIN is the input here, the 24 burst pulse need be cut to 20 pulse, the following 12 burst pulse be cut to 10 pulse, i wonder how to realize this as simple as possible. i thought of timer and digital filter, but have no idea yet. someone t
Assuming the delay is long enough that we humans can observe it... Then I would hook up an LED (with safety resistor inline) to the output. Connect the other end to ground. (Or connect it to V+ if that's how the output terminal operates.) An led is obvious when it is on, and it doesn't need much current. Or, does the timer operate on main
See attached a very simple voltage trigger alarm using TL431. You may add a timer module using for example the CD4060 circuit, to trigger the alarm in short beeps, followed by an adjustable stop time period and circuit restarting automatically over a period of time to keep monitoring as a remainder for charging the batteries.
The resistors at B creates a voltage divider which determines the value that is compared to the output of the timer. So it sets the point at which the comparator changes states. The resistor at C limits the current going to the base of the transistor.
Basically the whole operation of the 555 timer revolves around the three resistors that form a voltage divider across the power supply, each resistor ~5k (for the bipolar version of the IC) so the comparator reference voltages are 1/3 and 2/3 of the supply voltage. The pin 5 identified as ''Control Voltage Input'' can directly affect this relat
yes. when you want to use countup , then the loaded value is (max.value-desired count). when count down , it is "countvalue" only. both are valid. but countdown method has easier remembering for the count to be loaded. some controllers , like 8051 use countup for their timers(timer0). the maxcount-desired value is loaded in that.
It depends on application type. For example you want to do load management for high power devices. you need timer, function blocks or may be comparators. What kinds of logic you implement, decide the use of comparator, timer, registers, flags, and function blocks.
I assume you have read he datasheet Idle Mode When the SM2..0 bits are written to 000, the SLEEP instruction makes the MCU enter Idle mode, stopping the CPU but allowing SPI, USART, Analog comparator, ADC, Two- wire Serial Interface, timer/Counters, Watchdog, and the interrupt system to continue operating. This sleep mode basi
Hi I am having a 600 Hz signal, I want to generate Square wave by using 555 timer IC and duty cycle to be 70 % How to go abt it Thanks
i asked the tutor he said its the delay of the 555timer and flip-flop. that caused the phase shift between flip-flop output and comparator output. Doesn't sound reasonable. 4027 and 555 have delays in < 1us range, even the comparator response time is much faster than the delays viewn in your waveform. The circuit must be different f
You're mixing three losely related points in your last post. Consequently there's no reasonable answer to it. Referring to your original question, the modulation input is varying the threshold of the comparator ending the output pulse. Insofern, the instantaneous value of AC voltage matters, it's like being sampled. Unfortunately, the modulaion
I have many example on PIC16F877A. It's is C Code using Hi-Tech compiler. I use Hi-Tech because it's already integrate with the MPLab software. My Lesson. The sample include LED, 7 segment, switch, keypad, LCD, comparator, ADC, PWM, timer, Interrupt, EEPROM, UART, SPI, I2C, RFID reader, GSM (AT Command)