Someone told me this is where the smart people hang out. I am a rookie and this is my first post here after becoming frustrated with countless, fruitless web and forum searches.
I am looking for some help with setting up a series of NE555CP as audio-controlled pulse width modulators.
Here are the details of my project, followed by some questions, and a precursory schematic follows at the end of this post.
Supply is a 9V battery bypassed with a 100uF capacitor.
A low level audio input signal feeds a series of LM741 op amps which are separated within a voltage divider. When the input signal is low, the op amps' outputs are all high and the LED's are all off.
As the input level voltage increases, the op amps' outputs sequentially go low and the LED's light, as they do here, an LED "bar graph" driven by the audio signal's amplitude.
I have verified this works with white LED's on a breadboard, manually adjusting the input voltage on a DC power supply. I have not verified this with audio yet, but do not believe it will require much more than adjusting the values of the resistors in the voltage divider network to tweak in the levels. That is, unless there is an issue with the negative side of the sine wave. If all goes well, I will probably use potentiometers on the high and low ends of the divider to accomplish the necessary tweaks.
The next planning step I would like to take (but need assistance with) is moving to RGB LED's... specifically, I will break up the audio signal into 3 portions using bandpass filters. I would like to use each portion as a unique control to an NE555CP pulse width modulator, which will then feed pulsed voltage to one color of the RGB LED.
The effect I am looking for is that the bar graph goes up an down with signal amplitude and once PWM's are setup for R, G, and B, the color will shift or twinkle with sound frequency within each band.
Disclaimer: I have exactly zero experience with PWM or setting up a 555 timer in any mode other than astable.
So, a few questions:
1) Is my plan workable or are there obvious flaws?
2) How do I setup the timer with regard to the "Trigger" pin? I am using TI parts, but I am referencing Figure 9 of the Fairchild datasheet here. I am confused about how to use that "Trigger" pin (or if I even need to) and the formula for choosing the values of "RA" and "C". I would like to setup the frequency of the PWM to be above the audible range to avoid any crosstalk with the signal.
3) I recall seeing somewhere that I need a couple of diodes inserted into the circuit in order to increase the extents of the duty cycle on both the high and low ends? Where might these go?
Lastly, here is the schematic for the circuit so far. Notw that this includes only one of the colors and does not include any of the bandpass filtering I mentioned, but will rather serve as the basis for just one of the 3 colors.
Thanks vey much and in advance for any advice you may offer.
I am looking for some help with setting up a series of NE555CP as audio-controlled pulse width modulators.
Here are the details of my project, followed by some questions, and a precursory schematic follows at the end of this post.
Supply is a 9V battery bypassed with a 100uF capacitor.
A low level audio input signal feeds a series of LM741 op amps which are separated within a voltage divider. When the input signal is low, the op amps' outputs are all high and the LED's are all off.
As the input level voltage increases, the op amps' outputs sequentially go low and the LED's light, as they do here, an LED "bar graph" driven by the audio signal's amplitude.
I have verified this works with white LED's on a breadboard, manually adjusting the input voltage on a DC power supply. I have not verified this with audio yet, but do not believe it will require much more than adjusting the values of the resistors in the voltage divider network to tweak in the levels. That is, unless there is an issue with the negative side of the sine wave. If all goes well, I will probably use potentiometers on the high and low ends of the divider to accomplish the necessary tweaks.
The next planning step I would like to take (but need assistance with) is moving to RGB LED's... specifically, I will break up the audio signal into 3 portions using bandpass filters. I would like to use each portion as a unique control to an NE555CP pulse width modulator, which will then feed pulsed voltage to one color of the RGB LED.
The effect I am looking for is that the bar graph goes up an down with signal amplitude and once PWM's are setup for R, G, and B, the color will shift or twinkle with sound frequency within each band.
Disclaimer: I have exactly zero experience with PWM or setting up a 555 timer in any mode other than astable.
So, a few questions:
1) Is my plan workable or are there obvious flaws?
2) How do I setup the timer with regard to the "Trigger" pin? I am using TI parts, but I am referencing Figure 9 of the Fairchild datasheet here. I am confused about how to use that "Trigger" pin (or if I even need to) and the formula for choosing the values of "RA" and "C". I would like to setup the frequency of the PWM to be above the audible range to avoid any crosstalk with the signal.
3) I recall seeing somewhere that I need a couple of diodes inserted into the circuit in order to increase the extents of the duty cycle on both the high and low ends? Where might these go?
Lastly, here is the schematic for the circuit so far. Notw that this includes only one of the colors and does not include any of the bandpass filtering I mentioned, but will rather serve as the basis for just one of the 3 colors.
Thanks vey much and in advance for any advice you may offer.
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