Hi Everybody

I am very new to oscilloscopes and finding my way slowly.

Like many I have built my 555 timer circuit with 1k, 100k, 1uf cap and all working and went well. So it was time to use my oscilloscope and try and use a known state to understand how to start using it.

When I use my bench supply there appears to be ringing (pictured RHS), if I swap to using the USB output on the bench supply the ringing reduces but is still visible about 50% less (not pictured). But when I use USB from the PC (pictured LHS) it disappears.

I live in NZ (230V supply voltage and 50Hz) and my bench power supply is a WANPTEK APS3010H



Is my Power supply broken or Is it something else?

Thanks

 

That doesn’t look like ringing, it look like amplitude modulation.

Reduce the timebase by turning the HORIZONTAL SCALE knob until the waveform of the noise is expanded to be visible as the waveform on the display.

Use the VERTICAL POSITION knob as needed to center it, then use the HORIZONTAL POSITION knob as needed to get the wave form in proper view.

Use the VERTICAL SCALE know to increase the waveform size on the display. Pressing on this know will switch between coarse and fine adjustment to make it easier once you are close to the right size.

Take a photo of the resulting waveform—or better, insert a USB drive into the port on the front and press the green PRINT button to take a screenshot and save it to the drive.

 

Late here but will try tomorrow. I think what you are saying, apologies if not, if a square wave expand as wide as possible then set the time frame appropriately.

Had a stroke last year and determined to learn something new. Small steps and thanks for your patience as ever. Always useful to have terms so I can google and youtube.

 

Late here but will try tomorrow. I think what you are saying, apologies if not, if a square wave expand as wide as possible then set the time frame appropriately.

Had a stroke last year and determined to learn something new. Small steps and thanks for your patience as ever. Always useful to have terms so I can google and youtube.

Not quite. Not as wide as possible, as wide as needed to see the nature of the noise waveform.

 

An NE555 or LM555 are very old (designed 51 years ago in 1971) therefore use old TTL logic circuitry. Therefore they draw a current spike of 400mA each time the output switches that can overload your power supply wiring (simple breadboard?).
Adequate power supply bypassing is needed.

 

I have never observed a square wave signal looking like that.
It would appear that there is interference originating from another source and not from the 555-timer circuit.

 

I have never observed a square wave signal looking like that.
It would appear that there is interference originating from another source and not from the 555-timer circuit.

I think the interference is from the power supply that is being overloaded by the shoot-through current of the 555.

 

Not quite. Not as wide as possible, as wide as needed to see the nature of the noise waveform.

Hopefully what you suggested. On max width moves to the bottom.

 

Finally removing a much as I can from the bottom before the top becomes fuzzy (gosh need to learn terms) gives

 

You’ve going the wrong direction.

You need to expand the noise waveform by reducing the timebase. This is the HORIZONTAL SCALE knob. Try it this way:

First, adjust the VERTICAL POSITION knob until the top of the square wave is on the middle of the screen.
Next adjust the HORIZONTAL POSITION knob until one of the noise waveforms (top of the square wave) is centered on the screen.
Next adjust the HORIZONTAL SCALE until the noise waveform shows only one portion that is this part:

​

It will be stretched out, showing the detail but with a very low amplitude.

Finally, adjust the VERTICAL SCALE knob until the waveform is occupying about ⅔ of the screen, in the center which the flat part on the center line.

The result will be like a new waveform, and it will be the details of the noise.

 

I starting to remember school where I had a go, but failed to get the thing to do what the teacher said it would do.

Here is the top LHS of the square wave. I would turn the VERTICAL SCALE more but the signal races left to right if I do this.

In any case thanks for your patience.

 

With the 555 running from the 5V power supply, probe the 5V and show it here.