I found a lot of vu meter wiring guide like this one
https://goo.gl/images/EMoFom
But I really don't know how to get them as a single channel combined.
Sorry, I don't have any electronic engineering background
The LM3915 is ok stand-alone (10 single LEDs), but if you want to use an Arduino to drive your lights, then an MSGEQ7 (7 channels) might be a better option.
Leo..
That are two very different chips with very different application. One is a VU meter (more outputs go HIGH as the signal strength i.e. the volume increases), the other is a spectrum analyser (gives a value for the strength of each frequency band in the signal). Can't replace one with the other.
Suggested schematic with the resistor based voltage divider on the output of the LM3915:
J1 are the output pins of the LM3915 (double check this with the data sheet before building).
J2 is an analog input of the ATtiny.
R11 is a protection resistor (may not be needed but won't hurt); R10 is the lower half of the voltage divider.
The values of the resistors are the calculated values; R24 standard values are a bit different. Use nearby values, or use two resistors at each pin to make them closer to these values (mind that changing the value of R9 changes the output voltages of all other channels, except of course pin 10, as well).
No signal: all pins are low, voltage at J2 is 0V.
Little signal: pin 10 goes HIGH, voltage at J2 goes to 0.5V: voltage divider R9 and R10. Analog reading about 102.
More signal: pin 11 goes HIGH, voltage at J2 goes to 1.0V: voltage divider between parallel resistors R9 and R4, and R10. Analog reading about 204.
And so on - every one pin increases the voltage by 0.5V and the reading by 102, until it reaches 5V (Vcc) when all are on.
I assume Vcc is 5V, if it's 3.3V all steps will be 0.33V but the analog readings should remain the same.
wvmarle:
That are two very different chips with very different application. One is a VU meter (more outputs go HIGH as the signal strength i.e. the volume increases), the other is a spectrum analyser (gives a value for the strength of each frequency band in the signal). Can't replace one with the other.
Yes, I understand. I think I started using the LM391x family about 40 years ago.
Never used the MSGEQ7, but it should be able to do the same in software as the LM391X.
With the option of splitting/adding the 7 bands into 3 bands for an RGB LED strip.
Leo..
Ah, now I get your idea.
Indeed, should work - and if you combine all seven into a single band (average the values?) you almost get back a VU meter.
It does look like you need three pins to properly read the chip (one to provide "strobe" - a clock, one for the reset, and one for the chip's output).
Yes, number of channels and averaging or using the one with the highest peak can all be done in software.
Leo..
Thank you very much. I should slowly start doing this project of mine while waiting for the parts to arrive. I ordered a digispark attiny85 and considering to use on this project too.
wvmarle:
That are two very different chips with very different application. One is a VU meter (more outputs go HIGH as the signal strength i.e. the volume increases), the other is a spectrum analyser (gives a value for the strength of each frequency band in the signal). Can't replace one with the other.Suggested schematic with the resistor based voltage divider on the output of the LM3915:
J1 are the output pins of the LM3915 (double check this with the data sheet before building).
J2 is an analog input of the ATtiny.
R11 is a protection resistor (may not be needed but won't hurt); R10 is the lower half of the voltage divider.The values of the resistors are the calculated values; R24 standard values are a bit different. Use nearby values, or use two resistors at each pin to make them closer to these values (mind that changing the value of R9 changes the output voltages of all other channels, except of course pin 10, as well).
No signal: all pins are low, voltage at J2 is 0V.
Little signal: pin 10 goes HIGH, voltage at J2 goes to 0.5V: voltage divider R9 and R10. Analog reading about 102.
More signal: pin 11 goes HIGH, voltage at J2 goes to 1.0V: voltage divider between parallel resistors R9 and R4, and R10. Analog reading about 204.
And so on - every one pin increases the voltage by 0.5V and the reading by 102, until it reaches 5V (Vcc) when all are on.
I assume Vcc is 5V, if it's 3.3V all steps will be 0.33V but the analog readings should remain the same.
This looks like the single channel output, can be used directly on to the mosfet. Can I?
No.
MOSFETS are best used as on/off switches.
They have a linear part where their resistance drops with voltage but it starts at Vgs(th) which is well above 0V and ends below 5V (for a logic level MOSFET). In the linear area a MOSFET produces a lot of heat.
This is really meant to be read by a microprocessor, then turned into a PWM signal.
That said, I think I would prefer the MSGEQ7 solution by @Wawa for a project like this. Much less components involved.
Ok, I kinda understand that why mostfet needs to be controlled via pwm instead of continuous current. Basically with continuous current, it keeps receiving energy and thus it will generate heat?
I saw this schematic
https://goo.gl/images/9ibrvD
Basically I just use the analog out, the pin 3, into the analog in of the attiny85 to map the input coming from the MSGEQ7. I gotta agree that it is quite simple just to get a single pin output from audio signal.
The circuits however, is it possible to just follow from the link above?
sarf2k4:
Ok, I kinda understand that why mostfet needs to be controlled via pwm instead of continuous current. Basically with continuous current, it keeps receiving energy and thus it will generate heat?
Transistors (of the BJT type) are current controlled, MOSFETs are voltage controlled.
When not fully open they have a significant resistance. This resistance with the current flowing through them causes heat. When fully open the resistance is usually <0.5 Ohm (see data sheet for details) so if you're switching a 20-30A current they'll still get pretty hot.
Basically I just use the analog out, the pin 3, into the analog in of the attiny85 to map the input coming from the MSGEQ7. I gotta agree that it is quite simple just to get a single pin output from audio signal.
You obviously didn't read (or understand) the data sheet.
Strobe connects to one of your digital out pins, reset to another, "analog out" goes to a digital or analog in - both will work - it's an analog signal but it has the info of seven channels in it, so you'll have to read them all, take the average, and you have the loudness level.
Hi, I'm sorry about the long delay for this reply. I've found what is similar over here
But I'm not sure about the mic sensor I was thinking that this person used the conventional arduino mic sensor pretty much similar to this one here https://goo.gl/images/fFYrei
I've found a link to divide the headphone jack but I'm not sure how can I interpret the schematics here Reading Audio Singals from a Headphone Jack - Syntax & Programs - Arduino Forum