The post discusses a buzzer circuit with an incrementing beeping rate, which can be used in critical warning signalling applications. The idea was requested by Mr. Lee.
Buzzer with Progressive Beep Rate
- Could you help me with a circuit. I've been trying to find but so far had no luck! I need a pulsing piezo that will start with a short blip and then over a period of may be 2 minutes, progressively increase the frequency of blips to maybe then permanently on or just rapid blips, similar to a game type of timer where the blips get quicker as the seconds pass.
- I want to use it on a car(so 12volt) to indicate when an anti car jack type immobilizer is about to operate. I've got ideas for the main immobilser circuitry but i'm struggling with the rising pulse rate buzzer/piezo.
- To simplify it slightly i would just use a 12v piezo driven by the rising pulse circuit.from when power is connected the timing cycle can start and maybe a variable resistor to tweak the pulsing cycle?
- Any ideas would really really be appreciated-if you can help,
The Design
The requested design for a buzzer circuit with progressive or an incrementing beep rate can be basically implemented through a voltage to frequency converter circuit
Although you may find many variants of voltage to frequency converter circuits, these may not be entirely easy to build due to their fairly complex design or due to the inclusion of unpopular, obsolete IC in it.
An alternative easier way of achieving this function could be by modifying an existing IC 4060 astable circuit with a homemade LED/LDR optocoupler as shown above.
As can be seen in the diagram, the LED/LDR opto is triggered through a slow rising voltage across its LED leads, which in turn induces a correspondingly slow decreasing resistance on the attached LDR.
The slow decreasing resistance of the LDR causes the timing capacitor of the astable to charge at proportionately faster rate, which subsequently causes a proportionately progressing or augmenting frequency rate at the output of the IC 4060.
P1 is for fine tuning the timing delay between the progressive beeps, possibly this component could be completely eliminated.
C1 can be also tweaked for adjusting the delay period between the beeps in order to make them faster or slower as per the application requirement.
The indicated buzzer unit here may be procured readymade in the form of a piezo buzzer or this can be also built at home by following this simple buzzer circuit guide.
Update:
Another interesting way of implementing a progressive buzzer beeper circuit could be by using a IC 555 monostable circuit and apply a slow rising voltage at its pin#5 control input....will update the circuit soon here.
Hi Swagatam, I have tested what you told me for the “Buzzer with increased beep frequency” circuit by connecting a 100uF / 25V capacitor between pin # 5 and ground on the 555 but the frequency does not change..I just get a constant tone. Would you be so kind as to provide me with an electrical diagram?
Hi Nandu, you can replace the buzzer with an LED and check its blinking rate. You can try manually shorting the pin5 to ground and then remove the shorting, check the LED response in both the conditions, this will prove whether the pin5 response is effecting the output PWM or not. What the pin5 capacitor does is, short the pin5 to ground initially which reduces the pin3 output PWM, and as the capacitor charges, the PWM slowly broadens and gets wider and wider.
Thank you very much Swagatam..you are very kind to answer me … I understand that then we can dispense with the led-LDR optocoupler stage and the transistors, connected in normal astable configuration? Excuse me, my knowledge of electronics is basic .. I thought you had assembled and checked the circuit, that’s why I asked you .. Thank you very much.
You are welcome Nandu, yes you can use the LED/LDR concept with a transistorized astable circuit, or any other astable circuit.
Good afternoon Mr. Swagatam commented that you would upgrade the progressive buzzer circuit using a 555 monostable IC circuit. Have you done it yet? I have not been able to locate it among your projects .. I would be very interested in getting it .. Thank you very much
Hello Nandu, the IC 555 can be configured in the normal astable mode, and a buzzer connected across its pin#3 and ground. This will produce an intermittent beeping sound at a constant rate. However, if a 100uF/25V is connected between the pin#5 and ground, it will create a slow intermittent intervals when power is switched ON, and this intermittent rate will get faster and broader as the 100uF charges up. This is according to my assumptions
Hi Swagatam,
I was trying to use your “Buzzer with incrementing beep rate” circuit and I had problems with the CD4060. I tried several things, but was unable to make it oscillate(maybe it was oscillating too fast). I guess that would work correctly if pin 3 oscillates at a progressive rate. I just could not get it to work. I didn’t have a 10uF non polarized cap so I used two 10uF electrolytic back to back. It didn’t work, so I put seven 1uF ceramic caps in parallel, but it didn’t work. I noticed you suggested a 555 timer would work to do the same thing using a variable input to pin 5. I bread boarded it and decided to try varying the resistance between pin 6 and pin 7. It works great. I used a variable pot from pin 6 to the LDR and from the LDR to pin 7.
Hi Norman, a 4060 IC oscillator is very basic and straightforward design, if it didn’t work for you then there should be something not correct in your circuit connections or the IC may be duplicate. You should have first tried to build the basic oscillator design, then tried to move the pot up down manually to check if the the output varied progressively.
Hi Swagatam,
In the above circuit, you used a BC547 (NPN) transistor to power the LED optocoupler. What determines when you can use a NPN transistor to provide power and when you have to use a NPN/PNP combo pair to power a circuit?
Hi Norman, I have used NPN because the switching input is positive, so PNP won’t work, and the common-emitter mode of the BJT ensures that the emitter voltage varies in accordance with the rising falling waveform, producing an equivalent rising and falling illumination on the opto LED
Hi Swagatam,
I was looking at the above circuit and have a question. How does the LED in the LED/LDR opto coupler light when both sides of the LED are connected to the positive rail? Also would this circuit work with progressively driving a LED instead of driving a piezo?
Thank you Norman, it seems to be a drawing mistake, but never mind, I have added a correction message just under the image so that the viewers can take note of that.
olto interessante
Thank you!!
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