Louder push-pull self-drive piezo buzzer driver with CMOS gates. - Page 1
Forum section: electronics / projects

author: Zero999
author_rank: Super Contributor
timestamp: September 28, 2014, 05:33:55 pm
content: I discovered a new way to make a piezo driver which is louder and more efficient than the typical transistor driver and doesn't require any inductors or transformers.It's very simple, just a couple of logic gates, a resistor and the buzzer.I used the 74HC04 but it should also work with the old 4000 series.

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2014, 05:44:04 pm
content: Works and drives the piezo at it's resonant frequency by using it as the frequency determining element. Ther advantage of a transistor and inductor is that you can get a very high voltage from the transducer, limited only by the resistance of the inductor and the breakdown voltage of the piezo or the transistor, whichever is lower. you can use that to drive a piezo till it disintegrates from the energy pumped in.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 28, 2014, 07:32:48 pm
content: Now, can you do one for two-terminal disks?Tim

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2014, 09:12:49 pm
content: 5 minutes with a dremel and a small ball grinder to machine in the 3rd contact.........

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 29, 2014, 12:12:37 am
content: Not one for a challenge?Tim

author: Rerouter
author_rank: Super Contributor
timestamp: September 29, 2014, 08:56:30 am
content: I would imagine you could use a circuit that abuses the height of the voltage spike being returned to form some form of V/F circuit, only thing would be a way for the feedback to tell it to decrease the frequency or increase it,

author: Mad ID
author_rank: Regular Contributor
timestamp: September 29, 2014, 09:18:28 am
content: I'm using a standard magnetic buzzer with a transistor switch and back EMF diode with 50% D.C. PWM and 5V which is maximum rated. Besides not being loud enough the sound is metallic, i.e. it contains higher harmonics.You guys have any idea o how to solve it? Capacitor in parallel doesn't help.

author: Rerouter
author_rank: Super Contributor
timestamp: September 29, 2014, 11:02:26 am
content: Add a large capacitance in series to AC couple your signal, the fact that the buzzer is only being pushed in one direction will make it sound flatter than if it is both pushed and pulled around its resting location, for the volume issue, you can always transform your pwm circuit into a crude boost switchmode, to get say 10 or 15V across the buzzer for a small duty cycle,

author: Zero999
author_rank: Super Contributor
timestamp: September 29, 2014, 09:08:38 pm
content: Quote from: T3sl4co1l on September 28, 2014, 07:32:48 pmIt should be possible. The feedback can be taken by looking at the current flowing through the transducer. I don't know if it can easily done with logic gates though.

author: Mad ID
author_rank: Regular Contributor
timestamp: September 29, 2014, 10:09:49 pm
content: Quote from: Rerouter on September 29, 2014, 11:02:26 amThanks! I will try it out!

author: Seekonk
author_rank: Super Contributor
timestamp: September 30, 2014, 07:16:31 pm
content: That reminds me of a product we built. Final test techs would adjust a pot so the frequency was at resonance and the loudest. A year later the boards started coming back, no sound. I opened up several of the piezo and and lookes with a nice AO microscope, the wires had broken off from fatigue. Sure enough when they dug out the data sheet, the peak to peak voltage was over the factory max spec.