Hi, I saw this project for powering up and turning off an amplifier, I realized the project but I'm with a problem.
I wanted to use this code to turn on and turn off a subwoofer that unfortunately does not have this feature, but if i connect the subwoofer output signal of my av receiver, arduino does not detect anything, I expect the circuit to work because if connected to the pre output it reads the signal without problems.
I do not understand if it is because the subwoofer output only sends low frequencies, or if the signal is too low and therefore needs to be amplified. Do you have any idea about it? If you could help me I would be grateful.
Thanks
Hi, I saw this project
No good! The Arduino can be damaged by the negative half of the AC audio signal, and depending on the signal level the audio can also be "damaged" (distorted).
You need to [u]bias[/u] the Arduino input (two equal-value resistors and a capacitor... the 47nF cap is optional).
With the input biased the Analog Read Serial program should read about 512 with silence and with a signal the readings should jump-around "randomly" above & below that. From those readings you can determine the threshold to use in your software.
but if i connect the subwoofer output signal of my av receiver, arduino does not detect anything, I expect the circuit to work because if connected to the pre output it reads the signal without problems.
If you've got sound coming out of the subwoofer, obviously there's a signal. Your receiver's "bass management" does have to be configured if you want "normal bass" out of the sub. Otherwise you might only get the "point one" low frequency effects channel from DVDs & Blu-Rays and no subwoofer output with regular stereo music.
Or, what's wrong with using the pre-out signal? I assume you want the sub on anytime there's sound.
DVDdoug:
No good! The Arduino can be damaged by the negative half of the AC audio signal, and depending on the signal level the audio can also be "damaged" (distorted).
You need to [u]bias[/u] the Arduino input (two equal-value resistors and a capacitor... the 47nF cap is optional).
With the input biased the Analog Read Serial[/u]** program should read about 512 with silence and with a signal the readings should jump-around "randomly" above & below that. From those readings you can determine the threshold to use in your software.
I'm aware of this, I found it by reading a topic here only today, in fact I was already thinking about modifying my code to do this
DVDdoug:
If you've got sound coming out of the subwoofer, obviously there's a signal. Your receiver's "bass management" does have to be configured if you want "normal bass" out of the sub. Otherwise you might only get the "point one" low frequency effects channel from DVDs & Blu-Rays and no subwoofer output with regular stereo music.
The subwoofer receives a signal and output sound because it has been configured so.
So there is a signal, I do not understand why an analogread of the subwoofer output does not produce any result when that of a pre out does.
DVDdoug:
Or, what's wrong with using the pre-out signal? I assume you want the sub on anytime there's sound.
In my receiver the only preout I have is for zone 2, which can not output digital sources but only analog, so totally useless for me because I only have digital inputs.
So there is a signal, I do not understand why an analogread of the subwoofer output does not produce any result when that of a pre out does.
The only logical explanation is that the sub-out signal is lower than the pre-out signal, and too low to trigger your original software/circuit. Run Analog Read Serial and compare the levels.
The preamp-output should be about the same as sub-out, depending on the program material and the bass/sub/EQ settings. A "tape output" will generally be a LOT hotter because it's not volume-controlled.
No good! The Arduino can be damaged by the negative half of the AC audio signal, and depending on the signal level the audio can also be "damaged" (distorted).
So you are:-
I'm aware of this,
But you still insist in using yet another crappy Instructables. The people who write stuff like this one are electronic morons. It won't work and you are surprised! It is down to the grounding of the signal and the Arduino.
Bias the input with a 10K pull up and pull down and attach the audio through a capacitor ( 1uF or bigger ) then you stand a bit of a chance.
Grumpy_Mike:
I'm aware of this,
But you still insist in using yet another crappy Instructables. The people who write stuff like this one are electronic morons. It won't work and you are surprised! It is down to the grounding of the signal and the Arduino..
As I wrote I discovered this problem after finding that project on instructable and I was already working to fix it.
I bias the signal coming from the subwoofer output, with 2 100k resistors, so I have 512 as an analogue reading, when i connect the rca the reading drops drastically to something like 40 with the receiver off, while once turned on It's over 300.
It's not exactly the behavior I would have expected, I thought I had a reading of 512 even with the rca connected to the receiver turned off until it received a signal, at that time I thought I would receive readings both higher and lower than 512 depending on the audio signal.
I would like to understand this behavior if anyone could explain me
Grumpy_Mike:
Bias the input with a 10K pull up and pull down and attach the audio through a capacitor ( 1uF or bigger ) then you stand a bit of a chance.
What is the reason for adding a capacitor in series to the signal?
I bias the signal coming from the subwoofer output, with 2 100k resistors, so I have 512 as an analogue reading, when i connect the rca the reading drops drastically to something like 40 with the receiver off, while once turned on It's over 300.
It's not exactly the behavior I would have expected, I thought I had a reading of 512 even with the rca connected to the receiver turned off until it received a signal, at that time I thought I would receive readings both higher[/b] and lower than 512 depending on the audio signal.
Something's wrong with theseries capacitor... It might be installed backwards (if it's polarized), maybe it's defective, or maybe your wiring is wrong. ...Or maybe the capacitor is too big and you're not waiting long enough for it to charge-up.
What is the reason for adding a capacitor in series to the signal?
Without it, DC current may flow from the bias circuit into the amplifier's output. That will mess-up your 50/50 voltage divider and mess-up the bias.
And, it may place the bias on the audio signal going into your subwoofer amp (but probably not much with 100k resistors).
AWOL:
Blocking DC
Ok this makes sense, which condenser you suggest to use? Since it's the output of a subwoofer I would not want to filter low frequencies, at least this is a possible problem I think can happen but I might be completely wrong.
DVDdoug:
Something's wrong with theseries capacitor... It might be installed backwards (if it's polarized), maybe it's defective, or maybe your wiring is wrong. ...Or maybe the capacitor is too big and you're not waiting long enough for it to charge-up.
Without it, DC current may flow from the bias circuit into the amplifier's output. That will mess-up your 50/50 voltage divider and mess-up the bias.
And, it may place the bias on the audio signal going into your subwoofer amp (but probably not much with 100k resistors).
The capacitor had not yet been installed because the tests were made before your previous message.
I did not think an electrolytic capacitor would be fine though, apparently I was wrong
Ok this makes sense, which condenser you suggest to use?
I told you in reply #4, did you miss it?
Grumpy_Mike:
I told you in reply #4, did you miss it?
yes i'm sorry, toally missed it. 1uF or bigger, from the value i think you are talking electrolytic capacitor, isn't it better a non polarized like ceramic one? but i don't think that there is a ceramic one with that value, maybe tantallium or lower value?
It doesn't matter about the type, it just blocks the DC. The bigger it is the lower the frequency response. Polarised or not, it doesn't matter.
Grumpy_Mike:
It doesn't matter about the type, it just blocks the DC. The bigger it is the lower the frequency response. Polarised or not, it doesn't matter.
I have added the capacitor in series to the signal and the analogreads with both signal and no signal are always around the 512 and do not change when the subwoofer is playing so clearly something is wrong, I tried different values from 1uf up but nothing changed, I also tried to reverse the capacitor polarity but nothing happened.
So how have you wired it up? Is their a common ground between your Arduino and audio system?
Thanks that look OK as far as it goes but you have not answered
Is their a common ground between your Arduino and audio system?
Is that pin 2 a ground on the audio input? My guess that you are just connecting the two speaker wires to that connector which are push / pull. If so connect pin 2 to your audio ground leaving pin 1 to connect to one of the speaker wires.
taht is signal from the subwoofer out, it's an rca.
I connected the rca connector's center as signal to A0 (pin 1) and the outer collar to the arduino gnd (pin 2)
Rca is only the name of a physical connector type. Try connecting like I said in reply #15.
it's the subwoofer out of my av receiver, in theory in should be like line out but only for low frequency.
Directly connect the speaker output? It is not a much higher voltage than an analog pin can hold?
I am pretty sure it's much more than 2.5V (5V divided by 2, since the input bias is) but if i'm saying something wrong please correct me.
in theory in should be like line out but only for low frequency.
No, this is designed to be connected directly to a speaker, so it is in effect a differential input. If you are getting nothing then it is because you are not seeing any signal on the input. The A/D is working because you are seeing the 512 reference level so that only leaves the signal, it could be:-
- As I said in my last two replies
- Their is no signal coming out of the amplifier
- Things are not actually wired as you think and you showed.
