Pressure Cooker Whistle Counter Circuit

This circuit is designed to sense the whistles from a pressure cooker and count the number over a digital display. The system relieves the user from the stress of constantly monitoring the cooker and from manually counting the whistles.

The idea was requested by Mr. P.K. Bajpai

Design Concept

In many of the Asian countries rice is the staple food and to cook rice efficiently a pressure cooker is normally employed. We all know that a pressure cooker is preferred since it is able to cook food quickly through its high steam pressure inside. This saves energy and time both for the user.

Another advantage of this special cooking vessel is the facility to adjust the cooking degree or consistency of the food ingredient through an audible alarm in the form of whistles, also created by steam pressure.

The number of whistles allows the user to understand and optimize the texture and the efficiency of the food inside the cooker, and if this is not correctly estimated results in a bad quality food or sometimes even complete destruction of the food.

Electronic Counter for Counting Whistles

As per the request I have designed a simple and cheap whistle counter circuit that will relatively accurately respond to cooker whistles and trigger a digital counter for generating the data over the display.

Pressure Cooker whistle counter circuit

How the Circuit Works

Referring the image above, the design is basically built using two stages, a sound sensor circuit comprising T1, T2, T3, and a digital clock counter circuit using IC 4033.

The original circuit of the sound sensor was actually an ordinary MIC based amplifier designed to pick all sorts of sounds, and therefore the same design did not appear desirable for this particular project, since here I needed the device to sense only the high pitched whistles and not any other form of sound disturbances.

To modify the sound sensor into a customized whistle sensor I initially thought of applying LM 567 concept so that it filtered only the specific sound frequency.

However I did not want to make the design too complex, rather wanted to keep it simple and cheap, yet reasonably accurate.

This led me to think of an alternate solution using an opamp based high pass filter, but even this could have made the design complex, therefore ultimately I ended up designing a passive high pass filter using a capacitor and the resistor network for accomplishing the purpose.

You can see this inserted in the form C2/R7. This network makes sure that the only the high pitched, high frequency noise is able to pass through T2 and reach T3 for further amplification.

Other lower frequencies will be simply cut off and not allowed to cross the C2/R7 stage.

Before drawing the schematic I confirmed the result by imitating and  creating sharp verbal hissing sounds over the MIC, I was happy to see the connected LED effectively turned ON only to these noises, whereas the other normal loud sounds hardly succeeded to produce any effect. This confirmed the sound filter stage perfectly.

However the counter is not practically checked by me, but I can assure that it will work, since the design is a standard IC 4033 digital counter application design.

Parts List

R1 = 5k6,
R3 = 3M3,
R4, R8 = 33K,
R5 = 330 OHMS,
R6, R2 = 2K2,
R7 = 470K, R9 = 10K,
R10 = 1K,
R11 = 470 Ohms,
C1 = 0.1uF,
C2 = 330pF,
C3, C5 = 0.1uF ceramic
T1, T2 = BC547,
T3 = BC557,
IC1 = 4033
Mic = electret condenser MIC.
Display = 7 Segment Common Cathode Type,
Push Button = Push to ON type, Battery = 9V PP3 with switch

The Circuit was Successfully Tested and Built by Mr. Pradeep Bajpai.

The images of the built prototype can be witnessed below:

whistle counter prototype image

Video Clip:

The working proof of the above whistle sensor can be seen in the video which was also contributed by Mr. Pradeep Bajpai.

Need Help? Please send your queries through Comments for quick replies!


P K Bajpai said…
Hi Swagtamji ,saw pressure cooker whistle counter circuit designed by you as requsted by me yesterday. Thanks for such a quick response . I will assemble the same at the earliest ...P K Bajpai ,Lucknow.

Swag said…
You are welcome P.K. ji, let me know if you have any issues!
Pradeep Kumar Bajpai said…
Hi Swagtam ji , in the circuit 3 pins
of the IC are grounded but pin only 2 pin nos i.e. 8 & 14 are numbered but 3 rd pin no. has not been mentioned ( I think it is pin no. 2 )
Secondly C3 & C5 are 0.1 Mfd ceramic caps.Pl. let me know about C1 0.1Mfd if it also a ceramic cap. Thanking u again .....PKBajpai Lucknow.
Swag said…
Hi Pradeep ji, yes you are right, the missing pin number is pin#2. The 0.1uF capacitors can be ceramic type, or any other type, there are no restrictions for the components used.

Let me know if you have anymore problems.
brian johnson said…
How to make a electronic fishing float for night fishing..
Pradeep Kumar Bajpai said…
Swagtamji , value of R7 is not given under list of component . Cap C2 330pf and resistor R3 3M3 are not available can I use 470pf and 1M5×2=3M respectivily . Sorry for diturbing u again.
Swag said…
Pradeep ji, yes it seems I forgot to include R7 value, R7 can be 470k, or any close value will do. R3 is not critical, any value between 1M5 to 3M3 will do.

C2 is also not critical, 470pF will work

C2 and R7 determine the how well the circuit responds to cooker whistles specifically. Increasing R7, or decreasing C2 allows the circuit to become more responsive to shriller sounds
Swag said…
you can use a small SMD LED powered by a button cell and joule thief circuit, as explained here:

the above circuit will help the battery to last very very long.

the whole thing could be glued over a thremocole float.
Pradeep Kumar Bajpai said…
Swayam ji , IC 4033 B is not available can I use 4033 BE in place of it without any changes in the circuit ? Value of C4 has not been shown .Pl guide me .Thanking u.
Swag said…
Pradeep ji, all 4033 ICs will work,since all have similar working principle, so you can use any variant. C4 can be a 10uF/25V capacitor.

Please test the two stages separately and then join them together after confirmation, this will allow you to troubleshoot a possible fault quickly if any...
Pradeep Kumar Bajpai said…
Hi Swagatam ji ,finally I have assembled Pressure cooker whistle counter as per ur precious guidelines. I have made pcb by etching copper clad board by myself for easier assembling of components.I want to show u it's pics and a video. I opted a single MCB housing as it's cabinet . Provision to run on a 9v battery as well as 5v adopter has been made . LED indicators , to show that unit is running on battery or on adopter are also there. The max. range of operation is about 6- 7 ft .It works more efficiently when placed 2-3 ft distance. When it is moved beyond 2-3 ft it picksup surrounding noise and shows wrong counting of whistle . It also picksup sound of kitchen utensils or clicking of finger / clap . Can I send u video and pics on facebook?
Swag said…
That's great Pradeep ji, I am glad you could make it successfully.

Yes the response may not be extremely precise since we have not employed any special frequency detection stage. Nevertheless, you can adjust the response by suitably adjusting the values of C2/R7. Increasing R7 value or decreasing C2 value appropriately will help to reduce the unit's sensitivity for other noises.
Initially you can try replacing the existing R7 with a 1M resistor and check the response, and then accordingly fix the most favorable value through some trial and error.

You can definitely send the pics and even the video to my email, I would be glad to post them in the article for other viewers to see.

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