Question about new schematic- Metronome

[SparkyCal]

I am attempting to build this metronome on a breadboard.

https://www.thatraymond.com/2019/04/22/555-metronome

I have an initial question:

You will see a 100K and 18K component in the schematic. There is a line crossing out the initial values. I assume this means that the builder tweaked the initial design and used new values.

Is this your read as well? Also, the 100K and 18K components- are both of those potentiometers?

Thank-you.

P.S. Thanks Bertus for this link.

 

[bertus]

Hello,

The 18K is a fixed value that is determining the highest speed.
The 100K is a potentiometer to adjust the speed.

Bertus

 

[SparkyCal]

Thanks Bertrus. I breadboarded it and it is not working. The two LEDs light up, but there is no pulse. Rather, when I turn the pot, one of them brightens and dims with the turning of the pot, and the other does not seem to do much, but it is lit.

 

[SparkyCal]

Here is a pic

 

[bertus]

Hello,

Is the capacitor 22 uF as in the schematic?
When using a smaller capacitor, you will see the effect you see now.

bertus

 

[SparkyCal]

Hi Bertus- yes, the capacitor is the right value. However, I noticed errors in my wiring and that I had missed the second capacitor. When I re-wired it however, it still does not work . I have a purple and a green LED that have thre same ratings. Te purple one lights up and dims when I turn the pot. The green doesn't do much. The speaker makes no sound.

Also, my power supply has the attached read out- which may be an issue.

 

[bertus]

Hello,

You could enter the resistor and capacitor values in this online simulator to see how the bottom led would react:
https://visual555.tardate.com/

Bertus

 

[Audioguru]

Breadboards are a rats nest of wires all over the place. How can anybody see what connects to what?
Your power supply shows that something in the circuit (the 555 IC?) is heating with 0.73W which is almost smoking.

 

[SparkyCal]

@AG. I agree. Something is shorting. I may have to find another schematic because despite trying different cap values (Bertus- I just swapped out various values), the LEDs light but don't pulse. Perhaps an alternate schematic may be the next move.

 

[SparkyCal]

Going to try this one. It looks lien it is almost identical:
https://www.instructables.com/555-Timer-Metronome-Audio-Visual/

 

[Audioguru]

The schematic of the metronome schematic is very simple and is shown on many websites. Maybe the 555 is a fake or defective one from China (ebay, AliExpress, Banggood or Amazon)? Didn't you have an opamp from there that had the wrong part number on it?

The 22uF capacitor at pin 2 and pin 6 of the 555 is supposed to charge and discharge slowly through the pot and 18k resistor.
That is the capacitor that is not shown on your rats nest.

 

[SparkyCal]

Well, that one did not work as well. So either I'm defective, or thre circuit is- both are possible. lol

@AG...I am offended at the rat nest comment...lol- kidding.

I wired it twice since then, with all the components- and it does not work. Maybe the timer thing is the defect. But I'm sure I have used therein other circuits without issue.

On a more serious note, @AG- you may be right and perhaps it si the 555 timer that is defective (yes- came from China). Is there a test I can run to determine if the pins are working properly?

 

[bertus]

Hello,

Going to try this one. It looks lien it is almost identical:
https://www.instructables.com/555-Timer-Metronome-Audio-Visual/

The schematic looks the same. Only the series resistor with the potmeter is missing.
The series resistor should have a minimum value of 330 Ohms to protect the 555 and potmeter from burning out.

Bertus

 

[Audioguru]

In your circuit, a 555 should not draw a current higher than about 25mA but your power supply shows 81mA.
Is the power supply bad? Does it show 0mA without a load? Does it show 9mA when set to 9V and has a 1k load?
Maybe the 22uF capacitor to ground at pin 2 and pin 6 is 0uF, try another one.

I see a wiring error:

 

[SparkyCal]

Thanks AG and Bertus. I will try it again. The power supply is good, less than 4 months old.

 

[SparkyCal]

Well, the mystery si sort of solved. The 55 Timer is, in fact, flawed.

When I ran the wire to Pin 1 of the 555, rather than Pin 3, it worked. So, AG, it seems that you were right. The 555s I have are not normal.

Over and above that, the flashing and the audible ticks, are problematic. Usually, a metronome will have a one hit click that you can speed up or slow down. As in:

tick tick tick tick tick tick tick tick. and so on

However, this metronome delivers the ticks in pairs, as in:

tick/tick tick/tick tick/tick tick/tick....and so omn

Which makes it odd. Also, the LEDS follow the pattern, one LED trades going on and off with the other LED

It is useable, and I can get used to it, but it is not how I usually set up a metronome.

 

[SparkyCal]

The other issue is that it seems to start at 140BPM. A metronome should be able to start a lot slower and go upwards. I'd say 60bpm to 180BPM is a good range. But this starts at 140. Maybe the double click may be more workable at a slower bpm.

 

[SparkyCal]

I also noticed that if I remove one of the LEDs, it still works and it flashes just the one LED. I'm not sure if the designer of this circuit intentionally wanted the paired click, and perhaps that is why he had two LEDS. But I think a metronome is easier to work with if it had the one click that could be sped up or slowed.

 

[Audioguru]

Why is fake junk made in China and why does Amazon sell it?

The designer of the Metronome did not even try it.
Since the capacitor charges by the 1k resistor quickly but it discharges through the pot slowly, then the sound is click-click pause, click-click pause, click-click pause over and over. One LED lights for for a short duration then the other LED lights for much longer duration

The speed is slow when the pot is turned counter-clockwise if the slider terminal of the pot is connected to the correct end.

 

[SparkyCal]

@AG-I'm glad I tried it and we got it to work, but I've determined that this is not a good application for me. There are many ways to access a metronome, including free apps. I mainly wanted to see if we can get it going.