stu21t

i have this circuit board out of a light controller,
it has a microphone built into it so that it changes the colour of the lights to sound.
it is too sensitive at the mo, people talking in the same room set it off.
is there any way i can desensitise it?
theres nothing adjustable on it to turn down, and if i try and cover the mic with something it doesnt really work.
could i add a resistor inline with the mic or something?

foreigneRS

what's that bloody great variable resistor type thing do then?

stu21t

lol
that controls how fast the lights change colour when not on audio mode lol

stu21t

up for the mornin crew

ECU Monitor Enthusiast

iTrader: (1)

Stu,
Its hard without seeing the board myself more closely but generally ...

Find the 2 outputs of the mic, cut a track to isolate one of the connections.
Put a 47k resistor between the cut track and the mic then put another 47k resistor from the cut track non mic side to the other connection on the mic.

This modification in effect halves the output of the mic.

Resistors are standard 47k 1/4 watt carbon or metal film with 5 to 10% tolerance.

If you want me to be more specific then can you provide a close up of the rear of the board near the mic.

However, I think you will be better/easier using some kind of foam material to reduce sound to the mic but ensure non of the foam touches any other component other than the mic itself.



.

stu21t

hi si, thanks for the reply.
heres a pic of the back.
i think i know what you mean but would you be able to show me just so im sure.

ive circled the mic outputs co you know which they are.

St3V3_C

Looks like you might have to take the mic off the board to do what Simon is suggesting.

ECU Monitor Enthusiast

iTrader: (1)

Yes, what Steve said above is right as the tracks are hidden on the PCB top under the mic !

But I still reckon the best easiest way is to use some kind of foam to mute the sound

stu21t

i tried to cover it with foam but it didnt do it enough, it was still going off toooo much.


the dodgiest paintshop ever, lol


is that what you mean?
if not, lol
ive got a spare controller that im not using.
how do you fancy doing it for me si?
lol

ECU Monitor Enthusiast

iTrader: (1)

Yes thats right...

The chances are that the foam method although blocking the sound, is picking up vibrations from the board.

stu21t

I'm surprised I connect both legs together but if u say so lol.

If I do that with 47k resistor and it's still too sensitive do I put a 94k one instead? On 1 side or both?
Any resistor? Or does it need to be specific?

ECU Monitor Enthusiast

iTrader: (1)

You do but via a resistor.

This provides a load for the signal output to work agaisnt whilst the other resistor limits the voltage through and thus lowers its sensitivity.

This is called a potential divider.

To decrease the sensitity, increase the number of the vertical resistor in your drawing and to increase the level, make it a smaller value.

Use preferred values as these are cheapest... 22k, 47k, 100k, 220 k ... etc..

If you buy loads of 47k resistors.... you could use 2 in series to make 94 k or more by adding more !

Its trial and error I am afraid as there is probably an auto gain control input stage on that board that you are fighting against !

Also, consider that the software on the board may actually make the lights flash fast anyway on a single audio pulse so you may be on a loser to start with !

stu21t

Cheers mate,
If I fuck it up it doesn't matter cos I've got 2 boards and only need 1.

And it doesn't make them flash, it changes the colour from red-green-blue but at the moment it happens so fast that it just looks like it's a White flashing strobe effect.

So do I put the 47k on the horizontal and then change the vertical 1 up or down to change it, leavin the horizontal 1 alone.
If so I'll buy a pair of 47s and a 22&100 and have a play.

I'll give it a go and let u know how I get on

ECU Monitor Enthusiast

iTrader: (1)

Yes Stu thats spot on

Good luck

stu21t

Cool
Nice 1.
Thanks.

You'll laugh when you see where/what the lights are for lol.

stu21t

Can I use these?
http://mobile.maplin.co.uk/module.aspx?moduleno=5729
The 1s at the bottom of the page?

Hobomassiv

You could get a micro pot (the one you need a flathead to adjust) and stick it in there to have it fine tunable surely?

St3V3_C

Link fail lol.

What part codes?

stu21t

Works fine on my phone lol
Maybe take the mobile. Off if on a Pc?

http://maplin.co.uk/module.aspx?moduleno=5729

vaughant

iTrader: (1)

+1,variable pot should be fine,get one that goes up to say 1M ohm,plenty of play then.