Piezo Speaker Driver - Page 1
Forum section: electronics / beginners

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 11:58:20 am
content: Hi,i search a good way to get a piezo speaker as loud as possible with 7.4V and a 5V PWM/Sound signal 4kHz.At the moment this is my schematic, C1 is the Piezo.

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2015, 12:36:22 pm
content: Remove the diode.See link below:http://www.ryston.cz/pdf/avx/piezo.pdf

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 12:49:05 pm
content: Wow nice PDF.So i think i use this config:

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2015, 12:53:59 pm
content: Yes.Where are you getting the 4kHz from? Is this just a fixed frequency or variable? The transducer will be loudest, when driven at its resonant frequency.

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 12:57:06 pm
content: I've read that the human can hear this frequency the best.

author: AndyC_772
author_rank: Super Contributor
timestamp: April 17, 2015, 01:02:21 pm
content: Maybe, but that's irrelevant. A piezo transducer is a strongly resonant device, and only works effectively at its own resonant frequency.

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 01:03:42 pm
content: The piezo is rated to 30V so i think its ok with this config.

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 17, 2015, 05:12:13 pm
content: Depending on the task, 4Khz might not that good, that is allready a fairly high pitched sound.People do tend to register (not hear) lower frequencys better.

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 05:14:12 pm
content: I also think piezos are in the 4kHz range the most efficent (datasheed)

author: Seekonk
author_rank: Super Contributor
timestamp: April 17, 2015, 06:01:43 pm
content: The transducer will be loudest, when driven at its resonant frequency.We had a product we drove the piezo differentiallyl and had a pot to adjust freq for maximum volume. A year and a half later they were all coming back. With my microscope it was clear to see the wires attaching the crystal all had fatigue break.

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 06:04:26 pm
content: And what do you do against this fail?Can you show me your driver circuit?

author: eneuro
author_rank: Super Contributor
timestamp: April 17, 2015, 06:21:51 pm
content: I used last time magnetic transducer described in this threadhttps://www.eevblog.com/forum/projects/bestar-electronics-bmt1212h09-magnetic-transducer-polarity/and drive it using something like low current H-bridge on two pins of AVR ATTiny85, but it is not a piezo buzzer

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 06:25:40 pm
content: I have a ready to use case with included piezo, only the pcb is our work, so no chance to change this

author: Refrigerator
author_rank: Super Contributor
timestamp: April 17, 2015, 06:44:54 pm
content: Why not use an active buzzer? from what i know sometimes they are even too loud.

author: Zero999
author_rank: Super Contributor
timestamp: April 17, 2015, 06:57:25 pm
content: Does it have a feedback lead? If so, use a couple of logic gates to make a self-oscillating push-pull driver.

author: ripper121
author_rank: Contributor
timestamp: April 17, 2015, 06:59:24 pm
content: No, there is no feedback lead

author: Zero999
author_rank: Super Contributor
timestamp: April 18, 2015, 06:26:26 pm
content: The simplest solution is to look at the datasheet for the piezo for the resonant frequency.If you're using a microcontroller anyway, you could determine the resonant frequency.http://www.edn.com/design/integrated-circuit-design/4325890/Piezoelectric-driver-finds-buzzer-s-resonant-frequency

author: Teledog
author_rank: Regular Contributor
timestamp: April 19, 2015, 04:49:30 am
content: Not an expert on piezo, but they are capacitive (aka: lower impedance with increased frequency)Your typical audio amp kinda fails at higher frequencies when directly connected to a piezo (hence the big fat crossover LC units in the speakers).If you're just looking to run a single frequency (no, not into annoying dogs, as I have one) a basic LC piezo output thing here;http://williamson-labs.com/sdi.htm