Solve 555 Timer Problem - Get 100kHz & 95% Duty Cycle

In summary, the problem of designing a 555 timer on astable mode with an intended frequency of 100kHz and duty cycle of 95% has been solved. The necessary values were calculated, but the actual frequency achieved was 48kHz with a duty cycle of 93.5%. The max frequency for a 555 timer is 500kHz, so the issue was unclear. After testing with different capacitance values, it was found that using a 10nF or 100nF capacitor resulted in a frequency of 40kHz. However, after changing the IC and adjusting it in the lab, the desired frequency and duty cycle were achieved. It was also noted that the Multisim 555 design wizard was not correct
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[SOLVED] help 555 timer problem

hi all, i am designing a 555 on astable mode. it is designed to operate at 100kHz with a duty cycle of 95% ( and i get 48Khz and duty cycle 93.5%).

i calculated all the values necessary:

Ra = 12.987 kOhm
Rb = 721.5 Ohm
C = 1nF
F = 1.44/ ((Ra + 2Rb)*C)


i used thes formulas :

tH = 0.693*(Ra + Rb)*C
tL = 0.693*(Rb)*C

T = tH + tL


i searched everywhere and found out the max frequency is 500Khz so I am not sure where the problem is...i need the 100kHz because i am designing an infrared modulator and the central frequency for my filters is 100kHz


can anyone help me thanks.
 
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  • #2
1nF is a bit small, capacitors this small aren't very accurate and the effects of stray and gate capacitance start to matter, you might want to redesign it with at least 10nF.
 
  • #3
just tested with 10n and 100n ...got 40Khz this time...ive double checked everthing.


i just simulated it on multisim and i got 45.9kHz ...but by my calculations it should be 100kHz

any ideias? i think this is very odd
 
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  • #4
--SOLVED--

the multsim 555 design wizard is not correct. there is a problem with it... in the lab i changed the IC (it was a bit damaged) and i managed to adjust it to my desired frequency / dutycycle.

btw... thanks for trying to solve my problem
 

FAQ: Solve 555 Timer Problem - Get 100kHz & 95% Duty Cycle

How can I calculate the values needed to achieve 100kHz and 95% duty cycle with a 555 timer?

The formula for calculating the frequency of a 555 timer is F = 1.44/(R1+2R2)C, where R1 and R2 are the resistors and C is the capacitor. To achieve a 100kHz frequency, you will need to choose values for R1, R2, and C that satisfy this equation. Similarly, the duty cycle can be calculated using the formula D = (R1+R2)/(R1+2R2), and a value of 95% can be obtained by choosing appropriate values for R1 and R2.

What is the typical range of values for R1, R2, and C in a 555 timer circuit?

The typical values for R1 and R2 are in the range of 1kΩ to 100kΩ, while the typical range for C is between 1nF to 100nF. However, the specific values needed for your circuit will depend on the desired frequency and duty cycle.

How can I test the output frequency and duty cycle of my 555 timer circuit?

You can use an oscilloscope to measure the output frequency and duty cycle of your 555 timer circuit. Alternatively, you can also use a frequency meter to measure the frequency and a voltmeter to measure the duty cycle.

What are the main factors that can affect the accuracy of the frequency and duty cycle in a 555 timer circuit?

The accuracy of the frequency and duty cycle in a 555 timer circuit can be affected by factors such as the tolerance of the resistors and capacitors used, the supply voltage, and temperature changes. It is important to choose high-quality components and ensure stable operating conditions for the most accurate results.

Are there any alternative methods for achieving a 100kHz frequency and 95% duty cycle without using a 555 timer?

Yes, there are alternative methods for generating a signal with a 100kHz frequency and 95% duty cycle, such as using a microcontroller or a dedicated frequency generator IC. However, the 555 timer is a popular and cost-effective option for many applications, and mastering its use can be a valuable skill for a scientist or engineer.

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