for astable operation of 555

[pleasure]

astable operation

Hello to all !!!!!!!!
I have designed the astable multivibrator using 555 which has been modified for variable frequency and variable duty cycle ranging from 30 to 80% using two diode but problem is with me is i am not getting the desired output of pulses when i am trying to get for 5 kHz freq. but the same circuit is giving me the proper output when i am using it for 500 Hz (just by changing the value of RC). I am getting the output like charging and discharging of the capacitor instead of pulses when i am using it for 5 KHz . i am not getting why does it is happening? anybody can please solve my problem?

Thanks!!!!!!!!!!! [/b]

 

[GSM Man]

555 operation

Can you show us a schematic of your circuit?

 

[pleasure]

555 astable operation

hello dear!!!!!!
i have attached the ckt. dia. pls. check that and reply.
i have alson checked the same circuit with simulation but in actual it is not giving the output. i have changed the ic also.

Thanks!!!!!!!!!!!

 

[srikanthsamaga]

operationof 555

Using small value capacitor for high frequencies may work.....

 

[FANT]

555 astable troubleshoot

The output is from pin 3.
It is a square wave, are you sure not to have connected a broken probe to the output, with a false contact on the tip ?
This is because sometimes happens to use a weky contatc and the capacity of the cable between board and oscilloscope creates a low pass filter, in this case it resembles a triangle wave.

Mandi

 

[pleasure]

astable opration

hello to all!!!!!!!!
it is giving me the saw tooth kind of f waveform.
my component values are-
capacitor C=0.01 uF (polyester),R1=3K,R2+R3=20K(variable),R4=5.6k, for 5 KHz freq.
is this value is not okay?, I have caluclated the timing and frequency by this equations.

Ton=0.693 (R1+R2) C and Toff= 0.693 (R3+R4)C,

for C=0.1 micro F and resistance value as above am getting the desire output.

Please try to solve my problem its urgent!!!!!!!!!!!!!!

Thanks!!!!!