Lights when audio is triggered

[Paul Lockwood]

Hi

I'm new to the forum and fairly new to electronics.

To cover a bit of details I'm 45 and an IT engineer which covers all sorts from building / repairing computers, repairing phones if I can, support and some developing / programming.

It must be about 20+ years ago since I dabbled in electronics trying to make the odd thing on a breadboard. Think it may have been a timer.

Recently I've wanted to try and get into this more and been watching several YouTube videos, especially at https://www.youtube.com/user/mjlorton/playlists which has been most helpful on the basics.

I'm also about to order the Arduio UNO Starter kit as this looks quite interesting and the programming side will also be ideal for me too.

I would gladly welcome some comments on the Arduino side as I believe it is quite a big thing.

One project I do have in mind is as below which any help would me much appreciated.

For our phone system at work I've setup some laptops that produce live reports for the call centers so that they can see the calls coming in etc. I have some alerts on the report that basically can highlight a small part of the screen in a colour and also play a wav file to alert them of a problem.

What I would like to do is produce a more visual alert in the way of a flashing light which will light up over 6 desks (2 rows of 3 desks) so it needs to be reasonably bright but not blinding.

I had thought of somehow making a circuit to gather when the audio on the laptop plays a wav file, i.e.. plug into the 3.5mm jack on the laptop (will have to be a splitter so that the other half goes to some speakers to still play the audio). When the audio is triggered the circuit would then allow a light to be illuminated, the main issue here is that the sound being played is a short sharp boxing bell that rings once and I would like a light to either flash or just illuminate for a set time like 5 or 10 seconds.

I'm hoping I'm not asking too much or posting in the wrong area, but any assistance would be most appreciated. It would be nice to have an explanation as to what the circuit does rather than just be given a solution as I find that if you have a goal you learn better than just doing examples etc. that you can get that are not relevant to your needs.

Thanks in advance for any assistance.

Paul

 

[Arouse1973]

Hello. It might be as simple as a diode, capacitor and bleed resistor. So when the Bing Bong! sounds the capacitor charges through the diode and is bled off by the resistor. The bleed resistor ensures the Arduino has time to sense the voltage pulse and trigger the alarm.

A flashing strobe could be used to alert the people it needs to. Two things you need to be aware of is make sure the output level of the 3.5mm socket is below the maximum input of the Arduino port being used, if it isn't then you will need to attenuate the level with a potential divider.

Also if it's a weak signal, which I doubt, you may need to amplify the signal to the required level. Either way this is totally achievable.
Just an idea.
Adam

 

[Arouse1973]

Maybe something like this would do. The MOSFET would need to be a logic level type. I downloaded a bell WAV file and put this into the simulation. But you really need to see what the amplitude of the signal is first, you may need to adjust the component values but this is the easiest way I can think of doing it. VG1 is your speaker output connections and the 5 volt supply VS1 is from the Arduino
Adam

 

[Paul Lockwood]

Many Thanks Adam

This will certainly get me looking at something.
Is it easy / cheap to do a solution by not using the Arduino as this is a personal purchase for me to play around with and I was also looking for a long term solution to sit in the office.
We could use the USB port on the laptop for a 5v power supply but then I would guess that the lighting would be powered somehow else possibly 240v mains.

 

[Arouse1973]

The strobes I am on about run from 12 Volts (House Alarm Strobe) so you could power them from a wall-wart PSU and switch them from the Arduino using either a transistor, relay or opto-isolator etc. I thought you wanted to use an Arduino? You can do it without but will be more complex.
Adam

 

[KrisBlueNZ]

Hi Paul and welcome to Electronics Point

Thanks for your thorough and detailed project description. It's amazing how few questions we get with proper explanations like that.

I think you're onto something with your idea of splitting left and right channels and using one for user audio (I would use the left channel for that) and the other to control stuff.

If you want future expandability, you may want to consider using DTMF (telephone "touch tones") for your signalling on the second channel. You can generate DTMF audio easily with Audacity, and lay it down on the right channel of the WAV file you use as the alert. DTMF supports sixteen independent commands, which you can use individually to trigger an activation with an externally timed duration, or in pairs to turn something ON and OFF.

Dedicated DTMF receiver ICs are available (see http://www.digikey.com/product-detail/en/BU8872FS-E2/BU8872FS-E2CT-ND/3769142) but these tend to have limited lifespans. There is probably code available to run on an Arduino to receive and decode DTMF signals. You could even use other types of signals, such as modem audio using a dumb modem standard such as V.23 or similar (see http://www.digikey.com/product-detail/en/TDA5051AT/C1,518/568-10301-6-ND/4162493). Again, dumb modems don't have long product lifetimes and it would be better to use a software modem running inside an Arduino or Raspberry Pi for this.

If you just want to trigger one relay to close for a certain length of time, this can be done easily with a circuit with a couple of transistors. Adam's circuit in post #3 will work if the audio level from the headphone socket is high enough.

As for alarm annunciation, I guess you'll want to try things to see what works best. I can suggest one option I've seen, but I can't find it online. I guess I must be missing an important keyword. It's a cylindrical thing, several feet long, that's mounted vertically, and it is divided into segments, each surrounded by a cylinder of plastic of a different colour, with a light bulb inside each segment. Different alert priorites correspond to different colours, and the positions of the colours correspond to urgency. This makes it quick to see the highest priority alert level, and all the active alert levels.

 

[Paul Lockwood]

I've managed to test the Audio level on another laptop of the same model type and it's only reaching about 200mv which I would guess is not enough.
One thought I've had is (don't forget I'm totally new so may have the wrong idea and know how) if a transistor requires 0.6v to activate could that not be preloaded with 0.5v and then when the audio kicked in it would boost the level enough to trigger the transistor?

One way I had thought was if I use the Arduino it would be quite simple to program what to do if it received the signal.
On the second way if it was not used I could make the Audio file long enough for how long the action needed to be, this would play a high sound on the left channel which would be used to go through the circuit, the right channel could then just go off to a speaker to play the short sharp sound and the people around would be no wiser.

Looking at the diagram I guess that T1 is the MOSFET but what is VF1?

 

[Arouse1973]

Yes your right you could use an amplifier for this or my origional circuit using a comparator instead of the transistor. Or if you can program use the AtoD of the Arduino.
Adam