Electronic – Does the Low State in NE555 go to GND

555hardware

Here is the first schematic that I created : Circuit for 6s High state and 3s Low State using NE555 IC.

The Vcc is at 5.1V and I a self made using the LM317, Works Fine.

When I checked the Output with the Multi-meter I use., I was getting a high state of around 3.9V(Which I guess was fair enough.), but the Low was was giving an out of 2.5 ~ 2.6V, which to me seems a concern because the NE555 datasheet shows low state going to 0V in one of the graphs that shows the waveform in the astable operation..

I even tried simulating the circuit afterwards and this is what it looks like in simulation and even in the hardware set up :
Same values.

And what am I supposed to make out of this?
Voltage Low Level

So now I am getting a High state of 3.6V(seems fine), but the low state is still around 2.6V.

How do I find out the root of the Issue and how should I debug it?

Schematic of the 5V Power Supply being used.

Best Answer

With that particular circuit yes the output should go close to ground.

If it is not, either

  1. the 555 is sick or
  2. you MUST be pulling current from somewhere else... or
  3. perhaps the oscillator is still oscillating at some higher frequency, or,
  4. Your 5V supply is not flat DC.

Using a scope would help a lot.

You could try lifting the output pin and see if it still does it and measure what the voltage is at the top of the LED to eliminate item 2.

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