Controlling a piezo buzzer and a LED with a push-button.

quotidian

Aloha,
·
I’m a newbie. I searched the old posts but couldn’t find an answer to my question.
·
I want to control an LED and a Piezo buzzer simultaneously with a push-button. For example, when the button is pressed, the LED lights up and the buzzer makes a sound; when the user lets up on the button, the LED goes off and the buzzer is silent.
·
Here is the code I've been using:
·
DO
·IF (IN8 = 1) THEN 'If the button in Input8 is pressed then . . .
··· HIGH 7 'the LED in Input7 will light up
··· FREQOUT 12, 1000, 2000 'the speaker in Input12 will sound for 1 second (tone 2000)
·
· ELSE
··· LOW 7· 'the LED turns off
·
· ENDIF
·
LOOP
·
As expected, the buzzer sounds for 1 second and then turns off; the LED does the same. I reduced the FREQOUT duration to 100 milliseconds. Although this made the buzzer more responsive to letting up on the push-button, the sound was not adequate.
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Is there a way to “trick” the buzzer into “following” the commands of the push-button, without it losing its sound quality from the aforementioned code?
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Any suggestions, sample code, moral support, etc. is greatly appreciated.
·
Thanks in advance.
·
Dean

Chris Savage

Dean,

·· You probably won't get that kind of responsiveness without using an external buzzer of tone generator triggered by the I/O pin the same way the LED is.· The FREQOUT command requires a duration parameter.· You can't force it off by letting go of the button.· Sorry.· You could pull something like this off using an SX and SX/B though.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

FlyingFishFinger

Do you mean to light the LED and sound the buzzer for as long as the button is pressed ?
Rafael

quotidian

Thanks, Chris.

Rafael, yes that's what I mean.

Jon Williams

There will always be a bit of a pop between iterations of FREQOUT because it takes time to load instructions -- you'll never get a nice smooth tone.· You might try something like this:

Spkr······· PIN··· 12
StartBtn··· PIN··· 8
Led········ PIN··· 7

Setup:
· LOW Spkr
· LOW Led

Main:
· DO
··· Spkr = Spkr·^ StartBtn & StartBtn
··· Led = StartBtn
· LOOP

The first line toggles the speaker output -- but only when the start button is pressed (1).· The next line causes the LED to follow the start button; when start is pressed the LED will be on.

If the tone is too high you can insert short a short delay to extend the loop timing.

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Jon Williams
Applications Engineer, Parallax

FlyingFishFinger

You could put the IF statement in a loop with the freqout and use a short period ~100ms maybe, that would be the minimum tone length you can get (Each loop it checks the INx and activates the sound for the short time if IN=1, then loops). I wrote a test program and it kind of works
Rafael

quotidian

Thanks, Jon! That works exactly the way I wanted it to. One more question regarding tone control:

"If the tone is too high you can insert short a short delay to extend the loop timing." How would I do that?

Thanks, Rafael. Can you post the code for your test program?

Jon Williams

The simplest way is with PAUSE -- but bit numbers will make the frequency go low in a hurry.· Try this first:

Main:
· DO
··· Spkr = Spkr·^ StartBtn & StartBtn
··· Led = StartBtn
··· PAUSE 0
· LOOP

The PAUSE 0 line delays about 150 uSecs or so; this will reduce the tone but shouldn't reduce it too much.· Just understand that you probably can't get an exact pitch with an interpreted language -- you'd need the SX to do that.

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Jon Williams
Applications Engineer, Parallax

Paul Baker

Jon Williams (Parallax) said...


Main:
· DO
··· Spkr = Spkr·^ StartBtn & StartBtn
··· Led = StartBtn
··· PAUSE 0
· LOOP

Neat trick, always cool to see an out of the box approach.

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·1+1=10

Jon Williams

That one comes from our pal Dr. Tracy Allen

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Jon Williams
Applications Engineer, Parallax

FlyingFishFinger

Hello! My code works if you're not critical about minimum tone time and the slight skipping every so many seconds/miliseconds(time delay in freqout) that appears each time you loop.

Here:

' {$STAMP BS2p}
' {$PBASIC 2.5}
main:
IF IN1=1 THEN
FREQOUT 0,100,100
GOTO main
ELSE
GOTO main
ENDIF

Rafael

FlyingFishFinger

And you can insert the high/low statement for your LED: HIGH(pin) between "IF IN1=1"... and "FREQOUT...", the LOW(pin) between "FREQOUT..." and "GOTO main"

Rafael

P.S: The exact output frequency is dependant on the time delay and the given frequency value, so you'll have to play around a bit to find the desired frequency and an acceptable skip.

Chris Savage

Hello,

·· The frequency will also vary slightly depending on what else is running in a loop.· As you add other commands into the loop that will change the frequency some.· Right now the loop is simple.· Just something to keep in mind.

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Chris Savage
Parallax Tech Support
csavage@parallax.com