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Create Time delay using 555 timer IC

Vignesh_V
Associate II

Hi, I have create one adjustable multi vibrator circuit using 555 timer IC my aim is to achieve two things 

1.Basically 555 timer IC output is Rectangular wave my aim is achieve ontime of one pulse 0-10us(Micro seconds) time delay 

2.Another one is one pulse to another pulse generating time 10ms(Milli seconds )

So, How to achieve  this I am tried changes in resistor and capacitor value but  did not get proper time delay. I also Attached the circuit in below in document format .

1 REPLY 1
Peter BENSCH
ST Employee

Have you actually taken a close look at how the 555 works?

If you want to set the pulse length from 0...10us, not only should your Rchmin have zero ohms, but your diode in the charging branch should also have zero volts forward voltage, and Rctadj should also be adjustable from actual zero ohms. In reality your 100k potentiometer will have about 100...500 ohms in the minimum position, which at 1uF is already about 70...350us pulse duration. Then there is Rctadj with 2.2k, which adds another 1.5ms. The 700mV of the diode also changes this.

Although your discharge branch is separate from it, it leads to a fixed pulse pause that is set in each case, which together with the pulse duration results in a variable period duration. However, you actually wanted to achieve a constant period duration of 10ms.

All in all, this approach is not feasible. Why don't you first explain what the circuit is supposed to do?

Regards
/Peter

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