555 Design Assistant

    Given the recent contest at Hackaday.com, as well as my recent use of the 555 timer on the Knight Rider Scanner, I decided to put together a simple program to ease in the design of 555 timer circuits. Version 1.0 contains probably the 3 most common uses: Astable, MonoStable, and modified Astable allowing for duty cycles of less than 50%.
    This program is free to use in the hopes that it helps others understand a little better the 555 timer. I have also included the formulas used in the program if you wish to see how it is calculated.


Download
Must rename extension from .ex_ to .exe

    The astable circuit allows for varying R1, R2, and C. The program then calculates Frequency, Time on (t1), Time off (t2), and the duty cycle. It also generates a theoretical waveform to visually see the shape of the output.










    The modified astable circuit is the same as the astable with the addition of a diode across R2. This allows for a <50% duty cycle. The capacitor charges through R1 and the diode, and discharges through R2.
    Because of this, the charge time to 2/3 Vcc is dependent on the voltage of Vc + Vd (capacitor voltage + diode voltage). Since the diode voltage is constant, it must be considered in the charge time.
For example: a 5V Vcc with a silicon diode(.7v) means a Vc of 2/3Vcc - .7 = .66 x 5 - .7 = 2.63V (3.33V no diode or 21%)
    with a 10V Vcc, 2/3Vcc x 10 -.7 = 5.97V (6.66V no diode or 10%)
Therefore, the smaller the Vcc, the greater the impact.











   
Finally, the monostable circuit takes a signal pulse in, and creates a pulse width output of R x C.


Must rename extension from .ex_ to .exe







Copyright © 2011 by 100RandomTasks. All rights reserved.

   
Comments