Adding Volume LCD display ...

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.

skappy

Member
2004-01-20 12:38 pm
France
Hi everybody,
i'm just about to build amplifier based on the LM3886.
It should be a 5.1 type .
I would like to add to the basic amplier a general volume command and (this is where the thing come difficult) i would like to add a lcd which display the sound level (in Db for exemple).
I can think that it will require analogic to numeric conversion and binary to decimal conversion but i can't go further ...

Do you know where i can find help please ?

Thank you very much
 
Are you referring to a volume (sound pressure level) display or a output voltage (level) display?


If you want a SPL meter, you could hide an electret element somewhere in the room (perhaps even in the amplifier case) and calibrate it's output voltage with a good SPL meter. The output voltage can be fed into a A/D converter and treated accordingly.

You could also amplify the signal appropriately (from the electret element) and feed it into a LM3915 (log LED display driver).

If you just want a level output, the LM3915 is the easiest way to go.
 
Hi-
I'm actually doing/have done something similar. I have an amp that's got a bitmap LCD and is all digitally controlled. When you adjust the volume, a little bar increases/decreases and tells you dB level. Given that I had an LCD, I already had a microcontroller (8051 in my case)...The LCD connected via SPI to the micro. The audio did indeed come to the micro via A/D converter. Then you just have to write a basic algorithm to convert that binary number to dB. Pretty easy to do if you know a micro decently well. Anyway, that would be my solution, just use a microcontroller to do it.

Doovieman
 

skappy

Member
2004-01-20 12:38 pm
France
hi,
i have well understand your answer...
I agree that a micro controler can do the job but my big problem is that i don't master at all this kind of technology...
i can imagine how thing should be employ but i can't built the circuit..

do you know where i could find a kind of frame or examples in order to start in project ?

Thank you very much
 

owen

Member
2004-03-17 9:43 am
Shilton
Hiya,
I'd approach it in a slightly different way, but still using a micro - I'd use a digital volume control that can be controlled by the PIC (take a look at PiCAXe) and go from there...

It's easy to find rotary encoders that you can use for other functions too, to control the volume control...

Just a slightly different path - as you then know which volume setting you have (as well as balance etc) stored in the PIC.. much easier to output to a display!

Have fun

Owen
 
National Semi has a chip, the LM3915, which will will read out in 3dB increments, another of their chips will read out in VU. The LM3915 is intended to drive LED Bargraphs -- but you can translate the output (with a little "software in silicon") into numeric values for display on an LCD. without a microcontroller, however, getting the data onto the LCD display is a lot of work. as METAL points out you need to run the data serially -- this necessitates using a microcontroller (from any numer of sources). it is possible but a waste of time to do all the interfacing without a microcontroller.

you can quickly learn to program the Basic Stamp II -- and the company has a bulletin board with hundreds of members to help you out. unfortunately the Stamp doesn't have built in floating point math so you have to do a couple twists and turns to generate logarithms and exponentials. the URL is www.parallax.com

the BasicX BX24 from NetMedia www.basicx.com costs as much as a stamp but has the floating point math you need -- can be programmed over a serial cable like the stamp -- and has the benefit of 8 10-bit ADC's. The group of users is smaller, the programming language is a little more difficult, but the chip is very useful.

the folks from Netmedia and Parallax also sell LCD's, relay and servo drivers
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.