Help Please - building a simple motion detector

Thread Starter

mRoy62

Joined Dec 31, 2020
12
I am starting to develop my knowledge of electronics and would like to build a simple standalone (no RPi or Arduino). I understand that to vary the volume of a buzzer the buzzer needs to be passive and fed a PWM signal. I tried building one with an active buzzer and 10k ohm potentiometer, but that does not work. (I subsequently read that basically, an active buzzer is either on or off). I have built one using a passive buzzer with my RPi. I would now like to create one on a perf board so I can practice my soldering. Could someone take me up bit of a learning curve? I'm assuming I need some kind of chip (or other device?) that sends out a PWM signal. I would like to be able to control the volume using a 10k ohm potentiometer. The electronic components I have came with a RPi kit, so, hopefully, I have what I need to be able to do this. If not, I'll order what I need.
 

MrChips

Joined Oct 2, 2009
23,861
Welcome to AAC!

There are two types of piezoelectric devices (buzzers), (1) passive and (2) active.

1) Passive piezoelectric device is a transducer. It requires an oscillating voltage in order to produce sound. A simple circuit to drive the transducer can be made using a 555-timer IC. You control the sound level by controlling the voltage level to the transducer.

A 10kΩ potentiometer may or may not be the right value in order to control the voltage.

2) Active piezoelectric buzzer is the transducer plus the oscillator circuit. It requires a fixed DC voltage in order to power the oscillator. These devices are designed to emit a given sound level at the specified voltage. You may be able to modify the sound level somewhat by changing the supply voltage. Only by experimentation can you determine this.

A 10kΩ potentiometer may or may not be the right value in order to control the voltage. Again, it will depend on how the potentiometer is applied.
 

Alec_t

Joined Sep 17, 2013
12,148
Welcome to AAC!
The title of your thread is misleading. What has controlling volume to do with motion detection?
 

Thread Starter

mRoy62

Joined Dec 31, 2020
12
Where did you get that idea? A PWM signal is not a way to change the volume of a buzzer.

Bob
I got this from watching YouTube and reading articles. Could you help me understand a bit more? Thinking about this, I suspect that a varying PWM signal changes the tone - is that correct?
 

Thread Starter

mRoy62

Joined Dec 31, 2020
12
Welcome to AAC!
The title of your thread is misleading. What has controlling volume to do with motion detection?
Yes, you are right. Sorry about that. I managed to build a circuit with a motion detector and when motion is detected an LED lights and an active buzzer sounds. However, the buzzer is too loud. For some reason I had thought that using a passive buzzer may allow better control over volume.

what I am looking to build (and this is just to learn) is a motion detector with a volume controllable buzzer.
 

Thread Starter

mRoy62

Joined Dec 31, 2020
12
Are you wanting to use a Piezo as a Sound sensor??
I want to be able to control the volume level of 5v buzzer that is activated when motion is detected by a HC-SR501. I was initially envisioning using a potentiometer, but that didn’t work. I’m an absolute beginner and so hoping to use this project to learn.
 

MrChips

Joined Oct 2, 2009
23,861
The first thing is to identify the type of buzzer you have. Show us a photo of the buzzer.
Does it required 5VDC to operate?
Does it emit a buzzing noise or a high frequency tone?
 

Thread Starter

mRoy62

Joined Dec 31, 2020
12
One way of reducing the sound level of that transducer is to cover the hole with a piece of masking tape.
Yes, that would be a vey practical thing to do... and I will do that as a termporary solution. However, I am looking to grow my electronics knowledge and just using this as a way to do that. Perhaps I shouldn’t be using that buzzer at all... ultimately, I just want to be able to adjust the volume of a sound that is produced when motion is detected.
 
Top