Does a piezzo buzzer needs a protection diode - Page 1
Forum section: electronics / projects

author: rggmiranda
author_rank: Newbie
timestamp: July 23, 2015, 12:15:31 am
content: The question is really simple, i need to drive some piezzo buzzers from a transistor, and i would like to know if they need to use a diode protection like if they where an inductive load, i know they are not, but, even tough i read about it, i am not sure if piezzos cannot generate the same issue, please clarify me on that. Thanks!

author: BennVenn
author_rank: Regular Contributor
timestamp: July 23, 2015, 12:20:31 am
content: Is it a buzzer (has the oscillator circuit built in) or just the piezzo element (disc)?

author: rggmiranda
author_rank: Newbie
timestamp: July 23, 2015, 12:26:12 am
content: Quote from: BennVenn on July 23, 2015, 12:20:31 amI belive it has the oscillator built in, i just connect it to 5v dc

author: BennVenn
author_rank: Regular Contributor
timestamp: July 23, 2015, 01:04:38 am
content: then don't bother with a protection diode

author: rggmiranda
author_rank: Newbie
timestamp: July 23, 2015, 01:13:00 am
content: Quote from: BennVenn on July 23, 2015, 01:04:38 amOk, thanks you a lot, anyway, just for further knowledge, in the other case in which i had the piezzo itself, what would happen?

author: BennVenn
author_rank: Regular Contributor
timestamp: July 23, 2015, 01:55:39 am
content: Well that is intersting, the piezzo would be capacitive not inductive so you wouldn't get the back EMF that you would with a coil however if you drove it to resonance who knows!! Would be interesting to see on a scope

author: rggmiranda
author_rank: Newbie
timestamp: July 23, 2015, 02:15:38 am
content: Quote from: BennVenn on July 23, 2015, 01:55:39 amFor now, as i need it with the driver i will just avoid the diode, further on i may open one and check it with the scope, who knows maybe it can be harmfull, i will tell you the result, if you do it first tell me!Thanks for the info

author: TheMG
author_rank: Frequent Contributor
timestamp: July 23, 2015, 04:59:51 am
content: I've used such buzzers in many projects and have even seen them used in many very expensive pieces of commercial equipment, no diodes on any of them, never been a problem.

author: zapta
author_rank: Super Contributor
timestamp: July 23, 2015, 06:20:24 am
content: You also need to consider what will happen to your circuit if you will hit the piezo and it will generate high voltage exceeding less say Vce. That is the piezo is also a voltage source, not just load.

author: Zero999
author_rank: Super Contributor
timestamp: July 23, 2015, 07:52:01 am
content: A piezo buzzer with built-in driver contains a transistor oscillator and a transducer with a feedback pin which makes building the oscillator easier - it's just an amplifier with the input connected to the transducer's feedback pin.The only time a piezo buzzer contains a coil is to boost the voltage to get more sound but still no diode is needed as the transducer absorbs the extra voltage.

author: zapta
author_rank: Super Contributor
timestamp: July 25, 2015, 06:20:50 am
content: From Murata:Quotehttp://www.murata.com/en-us/support/faqs/products/sound/sounder/char/sch0001

author: Zero999
author_rank: Super Contributor
timestamp: July 25, 2015, 09:36:10 am
content: Quote from: zapta on July 25, 2015, 06:20:50 amThat only applies to piezo transducers which don't include a built-in oscillator.

author: Psi
author_rank: Super Contributor
timestamp: July 26, 2015, 01:07:32 am
content: Here's a piezo being driven directly from a AtMega I/O pin at 3.5khzLooks like it will be touching the clamping diodes on switch-off, about -1V