newbie SPL meter harware hacking

Hello Jame,

if you are still working on this I might be able to help. Due to E14's slightly odd way of hiding things I only blundered into you post today.

I'm sorry to say that you've picked a difficult device to hack into - was it cheap - it's surprsingly complex.

The LCD connects though the plastic to the row of pads on the pcb  - the magic is that the plastic contains conducting threads which run from top to bottom but not sideways and are insulated from each other. The threads are much smaller than the pcb pads so if you just sandwich the plastic between two rows of pads which are roughly alligned they end up connected. The LCD will have a row of pads which might be very hard to see.

You could pick up signals from the LCD driver chip (on the row of pads) but they will be very hard to decode and may not be simply digital (there aren't many pads so the LCD drive will probably be multiplexed which involves multiple voltage levels).

It might be easier just to build a sound level front end for the Arduino.

MK

Hello michaelkellett,

Very cool info about LCD. I never knew that.

And after some time of probing using meter, I could get some readings from of the the outputs in one of the op amps. And now, as you recommended I thinking to buid an stand alone SPL meter to hook it up to an arduino (if I succeed).

Thanks for reply.

Hello michaelkellett,

Very cool info about LCD. I never knew that.

And after some time of probing using meter, I could get some readings from of the the outputs in one of the op amps. And now, as you recommended I thinking to buid an stand alone SPL meter to hook it up to an arduino (if I succeed).

Thanks for reply.

I'm not sure how experienced you are at building circuits but you might find the Analog devices AD8307 is a good part to use. You can make a wide range sound level meter with one chip using this part. It is a bit expensive (about £11).

Look at fig. 44 on the datasheet.

I doubt if this part will work on breadboard so you would need to make or perhaps buy a pcb.

http://www.analog.com/en/rfif-components/detectors/ad8307/products/product.html

Ask again if you fancy trying this part and need some more info.

MK

Jamie

Is it possible to get a clear picture 3 (under the rubber band).

The markings on the board tend to suggest the pins may be common to other types.

You will still have to decipher the code sent, and in the end it may be easier as others have said to measure it.

I'm curious about the contacts in lower left of picture 2 (level +, Level -, FS, AC).

The HobbyKing picture doesn't show any pushbuttons.

It appears they go straight into the uP, so may be digital data.

mark

edit to replace the missing bits ....