Boe-Bot beeper volume is pretty low

Les · 2013-08-02 06:28

I hope this is the proper place for this.
How loud is the piezo beeper supplied with the Boe-Bot supposed to be? I admit that I have poor hearing, but I didn't think it was that bad. Hooking it up per the "program start/reset notification" example in the Boe-Bot book, I can only hear it if I put it right up to my ear.
Wife says she can hear it from across the room (show off), but that it is pretty soft.
I have used similar beepers in other projects in the past which seemed pretty loud to me. I just wondered if maybe I got a weak one or maybe it isn't supposed to be very loud in the first place. I realize that this is a plain "element only" piezo unit, not one with the built in driver, so maybe it is inherently soft.
Or maybe my hearing has gotten worse. Last time I had it checked it rolled off at about 8khz, 3khz shouldn't be a problem.
I am using an LED (with appropriate dropping resistor) instead for now.

Duane Degn · 2013-08-02 10:09

How is the piezo wired and what code are you using to control it?

I know with the Prop, I usually use a transistor to drive the piezo. I'm not sure if a transistor is needed when using the piezo speaker with the Basic Stamp or not.

erco · 2013-08-02 10:57

IIRC a piezo will be significantly louder at its resonant frequency, pretty high. oMaybe 10khz r 20khz. Try a frequency sweep and see what works best for you.

Genetix · 2013-08-02 12:01

According to the datasheet the resonant frequency is 4000 +/- 500 Hz.

http://forums.parallax.com/showthread.php/140150-What-are-the-specs-for-the-piezo-speaker-in-Activity-Kit

erco · 2013-08-02 14:51

IFTRC

(I failed to recall correctly)

Thanks for the followup, Genetix!

Les · 2013-08-02 16:05

Thanks for the replies.
I tried varying the frequency up and down in 500hz steps with no improvement. No point going past 6khz since my hearing rolls off at about 8khz anyway.
Per the book, the piezo is connected between P4 and ground, the code is simply:

FREQOUT 4, 2000, 3000

I'm sure the BS2 isn't driving the piezo very hard, I was just surprised that it was so quiet, wondering if my hearing had gotten that much worse without me realizing it.

tonyp12 · 2013-08-02 16:35

>connected between P4 and ground
Try P4 and P5 with complimented outputs.
e.g. 10 and then 01 as a AC signal will make a speaker louder.

Duane Degn · 2013-08-02 16:38

Here's a thread about increasing the volume of a piezo speaker.

I use a different schematic. The one I use has a transistor. I'll try to find the schematic and post it here.

Duane Degn · 2013-08-02 16:39

tonyp12 wrote: »

>connected between P4 and ground
Try P4 and P5 with complimented outputs.
e.g. 10 and then 01 as a AC signal will make a speaker louder.

Can you do this with a BS2? I thought this was a Propeller only trick.

Les · 2013-08-02 17:13

That's ok Duane, I know how to add the transistor. I was just wondering if maybe I got a weak piezo.

Duane Degn · 2013-08-02 17:27

Les wrote: »

That's ok Duane, I know how to add the transistor. I was just wondering if maybe I got a weak piezo.

Here's the schematic I have.




                       Vin(+5.0V)
                          &#61463; 
                          &#9474;   1K&#937;
                          &#9500;&#9472;&#9472;&#9472;&#61629;&#61630;&#9472;&#9472;&#9488;
                          &#9474; &#9484;&#9472;&#9472;&#9472;&#9488; &#9474;                               
                          &#9492;&#9472;&#9532;&#61620;&#8227;&#61615;&#9532;&#9472;&#9508;Piezo Speaker     
                            &#9492;&#9472;&#9472;&#9472;&#9496; &#9474;                          
   Microcontroller Pin &#61615;&#9472;&#9472;&#9472;&#9472;&#9472;&#9472;&#61629;&#61630;&#9472;&#61468;&#61470; 2N3904              
                             10K&#937; &#9474;
                                  &#9474;
                                  &#61464;
                                 Vss

The piezo speaker is the box under the 1K resistor. (I didn't have a good piezo symbol to use.) The 1K resistor connects connects across the piezo leads.

I think that's the circuit I use.

Do you have a different transistor piezo circuit in mind?

I doubt your piezo is weaker than normal. I've seen several others comment on how soft the sound from the piezo can be.

Les · 2013-08-02 20:54

Duane, your schematic is a little unclear, but yes, that's the general idea.
I'm perfectly happy using the LED instead of the piezo, so I'm good.

Duane Degn · 2013-08-02 21:33

Les wrote: »

Duane, your schematic is a little unclear, but yes, that's the general idea.
I'm perfectly happy using the LED instead of the piezo, so I'm good.

LEDs are great too.

I did try to clarify the schematic a bit in case anyone else is interested.

Genetix · 2013-08-02 21:48

Bit Rot - Time to replace the core memory, Erco :P

You can also try the circuit Beau Schwabe suggests in Post #4.

http://forums.parallax.com/showthread.php/62310-Amplifying-piezo-speaker?p=464410&viewfull=1#post464410

There is also this link where people suggest different fixes.

http://forums.parallax.com/showthread.php/107689-BS2-amp-Piezo-Speaker

Here's one using an Op-Amp but you need a dual polarity power supply.

http://forums.parallax.com/showthread.php/75707-How-to-Amplifying-a-Piezo-Speaker-and-Volume-Control?p=517152#post517152

Les · 2013-08-03 06:49

I'll probably add one of the amplifier circuits later when I get the Boe-Bot wondering about the house.
Thanks for all the input.

erco · 2013-08-03 07:47

Get a "hamburger speaker" off ebay for $4 and you will hear everything. Self contained amplified speaker, USB rechargeable.

http://www.ebay.com/sch/i.html?_sop=15&_sacat=0&_from=R40&_nkw=hamburger+speaker&LH_BIN=1

Whit · 2013-08-03 13:29

Just to cover all bases - is the cleaning sticker removed?

Les · 2013-08-03 15:09

Good point Whit, but yeah, did that first thing.

Whit · 2013-08-04 17:13

I only asked cause I've done it! Doh!

Boe-Bot beeper volume is pretty low

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