Coron 10 breadboard build - sound pulse?

[Hemmel]

Let me guess: A cheap microcontroller and a LED display. That'll be about it. The microcontroller reads the voltage using an ADC input at maybe 10or 12 bit accuracy if you're lucky, then outputs the reading by turning on the relevant LEDs. The rest is firmware.

The noise is digital hash caused by the microcontroller switching lots of LEDs on and off rapidly, I expect.

I'm trying to find where I bought those so I can provide a link but I'm betting you're right.
I noticed that the noise had a pulse that sync'd with the changes on the LED display.

[bluebunny]

Is it worth trying a couple of ferrite beads in the power lines (to block the HF crud), like they do in Eurorack land?

[Hemmel]

So I tried putting the tester in series with a 10µF cap and a resistor, and other components eventually.
It seems as if it won't capture the voltage if it's not directly on the 9V rail. Even in series with a tiny 1nF cap it couldn't read the voltage.

So, I'm abandoning the idea of having that voltage tester on my breadboard. Too bad.

[bluebunny]

Do you mean really in series?  I think it was intended for the resistor to be in series, but the cap to ground (i.e. a simple filter).

[GibsonGM]

I think there's misunderstanding Marc.  The meter will make 'clock noise' as it works, that's what it does. Like a low frequency oscillator (LFO) in a chorus pedal etc.

Our goal is to get rid of the little current spikes that happen as things like this operate.

Leaving the meter as it was (assuming it worked...), measuring PS voltage, you have a line delivering power to the breadboard.  Where it plugs in, try adding something like a 100 ohm resistor in series, followed by a cap to ground (try 100u, 10u, 22u, whatever for this).  Then you take power from that 'node' to your circuit.   See if the ticking is minimized or gone.  What you are doing is making the cap you add act like a reservoir, which will deliver its stored voltage to the following circuit when the meter pulls current do its measurement 3x a second or whatever the rate is. Like a tiny battery....the 'tick' is a spike where the voltage rapidly changes - we want to reduce those spikes, the cap does that.

You can't measure the voltage THRU a cap, no...caps allow AC voltage to pass, but a stead voltage (DC) just charges one plate and stays that way (italics) til something changes following it, and then it will discharge.

[GibsonGM]

Like this. Sorry for 4-yr old drawing, I broke my arm and am doing it left handed.  Watch that the cap's "minus" goes to ground.

[Hemmel]

I'll try this out tonight, thanks!

[antonis]

Woowww...!!!
Not only a professionl painter but a Cubist artist, also..

On the other hand, if "Plus" goes to circuit but "minus" ends up on cap we deal with an Abstract artist..

[GibsonGM]

This is not my work - I found it painted in a cave in France...

[Hemmel]

I'll try this out tonight, thanks!

Welp, just tried this and the pulse is still coming through in the circuit.

I'll simply abandon the idea of having the meter on my breadboard.
Or get another meter!

[GibsonGM]

In some circuits, you need to use a 100 ohm resistor and 1000u or higher cap...you can add more capacitance...

[Hemmel]

In some circuits, you need to use a 100 ohm resistor and 1000u or higher cap...you can add more capacitance...

I tried this but with a 470µF (largest cap I had) and ... it amplified the pulse!

I'll just abandon the voltage meter.

Maybe get back to it one day.

[GibsonGM]

I agree After some more DIY'ing and learning you may come back to it. it's hard to know exactly what you have at the moment...it should be do-able, but there may be a few factors we're not seeing here.   The idea of using an R-C filter like that to reduce spikes is something you can explore later on.  Remember it for builds you try out that might have similar symptoms....it's under the topic of 'power filtering'...good luck!