@#12

Thank you for your response, confirming my guess about why it doesn't work.

@GopherT

Sample-and-Hold circuit. Noted. I will look into this if I am ahead of schedule as I know people with spare 555s.

 

What I said, a precision rectifier with a capacitive time constant, is just another way to describe a sample-and-hold. (I don't think in the same terms as educated people because I am self-taught.) The leak-off rate of that circuit can be adjusted with a resistance in parallel with the holding capacitor to get a fade away effect, or you can do a long hold (with no resistor in parallel with the capacitor) which is defeated with a sudden dump of the charge (in the capacitor) with Gopher's idea. That will get you more of a bouncing dot effect. I can't imagine either of these circuits without a potentiometer to adjust the dump rate. Imagine the difference in rate from a slow song to a fast song. (Forgive me for being about 100 years old.) Moody Blues, Knights in White Satin at 56 counts per minute (MM56) compared to I'm Just a Singer in a Rock and Roll Band (MM135).

 

@#12

Before anything, being self-taught is great and that makes you educated as well (though you probably meant professionally taught/educated). It's awesome how seemingly knowledgeable (based on your replies to my thread) about electronics you are despite being a singer (not that it's a bad thing).

Back to the subject, I will experiment with the circuit and see what I can achieve! Your explanations greatly guided me to sketch some ideas out! I'll report back next week when I get my hands on the components. Hopefully I can get something out of it and make the Dot Mode work!

 

Read slower. I'm not a singer. That's a song title.

 

@#12
My mistake. No wonder the words were capitalized. Still doesn't change the face that you're self-taught *props*

 

@#12
My mistake. No wonder the words were capitalized. Still doesn't change the face that you're self-taught *props*

Here is a sample and hold circuit.
Your input signal is highlighted (from your LM324) amp - appears as a 400Hz signal source.



Sample-and-hold circuit




Reset circuit (the sample-and-hold circuit is reset). The 1M pot lets you select how often the peak is reset

 

@GopherT

In my circuit, I'll have add additional resistors and capacitors for the amplified gain (otherwise the signal wouldn't be strong enough) correct?

Also, what is that transistor-looking symbol? Reminds me of a MOSFET but it clearly isn't one...

 

@GopherT

In my circuit, I'll have add additional resistors and capacitors for the amplified gain (otherwise the signal wouldn't be strong enough) correct?

Also, what is that transistor-looking symbol? Reminds me of a MOSFET but it clearly isn't one...

You will use your whole Op amp circuit from way above (resistors and all) and feed that into the op amp (+) input.

There are two diodes in my drawing (one coming out of the op amp, one to the left of the 555 timer). You can use a 1N4001 - 1N4007 for those. Or, a 1N4148 or 1N914. Almost any smaller diode will be fine as long as it is not a Zener diode.

The outputs of the 555 goes to a 1k resistor and that 1k resistor is connected to a MOSFET. A small one is all that is needed. A 2N7000 would be good. You need it to turn on quickly at the 5v transistion of the 555 timer. If you have something else at hand, you can use that too. A mosfet will be best so it can nearly completely drain the capacitor down to ground. A BIpolar transistor will not drain the capacitor completely and you will always have a few segments lit on the ?LEDS FOR YOU LM3915.

 

@GopherT

So I tried my try at the circuit (which did no difference at all), then attempted to test out your version of the circuit.

Yours makes my Dot Mode work (yay!), but the 1M potentiometer makes no difference...As a matter of fact, I can remove half of these components and it'll behave the same (including the MOSFET). The rate at which the peak is held and reset is seemingly set at a defined point and cannot be changed with the pot.

In addition, the diode for the output of the comparator renders the circuit nonfunctional. With accidental experiment, a large resistor (1.5M) was put in parallel to the diode and the circuit now works. If I was to leave your circuit as it is, the LEDs would slowly climb their way to the top LED as if there was a capacitor charging somewhere.

P.S. I am running on a 12VDC supply which may make a difference + the LEDs lighting up one-by-one when using a diode happened before in my draft circuit designs.

I am happy with the results, but not with my understanding on what's happening to the circuit. I have wondered whether I connected something wrong (restarted 3 times) including the MOSFET (tried three different ones, flipped/unflipped assuming I might have connected ground to source).

 

The 100 nF is likely too big for the cap on bottom right (the hold capacitor).

Ok, you have created a filter. It is not a sample and hole, but a slow degradation of the signal. Easy and works. For a 1/10 second update, just set the cap and resistor values to values that, when multiplied together, they equal about what you want in update time.

For example, 100,0000 ohms x 0.0000001 farads = 0.1 seconds.

Note, 0.0000001 farads is 100 nano farads. capacitance in Farads.

 

@GopherT

Yes, a simple filter is what it is, though I have no idea why the sample-and-hold circuit is acting this way. I'll have to disregard this issue for now and keep on going.

The filter is working fine and DOT Mode is working better than ever!
Though the issue of the logarithmic scale on the LM3915 is still present (which cannot be fixed as it's part of the IC). My colleague recommended me to try with the LM3916 as its scale seems to be better for VU meters. I will try the IC tomorrow and see the difference.

In any case, my circuit is done and I will be working on the physical aspect of the project (which I will update time to time). Thank you guys for the great help!

P.S. I will post the final circuit and all once they've been finalized.

 

@GopherT

Yes, a simple filter is what it is, though I have no idea why the sample-and-hold circuit is acting this way. I'll have to disregard this issue for now and keep on going.

The filter is working fine and DOT Mode is working better than ever!
Though the issue of the logarithmic scale on the LM3915 is still present (which cannot be fixed as it's part of the IC). My colleague recommended me to try with the LM3916 as its scale seems to be better for VU meters. I will try the IC tomorrow and see the difference.

In any case, my circuit is done and I will be working on the physical aspect of the project (which I will update time to time). Thank you guys for the great help!

P.S. I will post the final circuit and all once they've been finalized.

Glad to hear all is working. The LM3916 part is better suited (see post 4 of this thread). I hope it works out for you.

Next, project. Make a 5-channel filter and VU meter for each frequency range