Building a Counting Circuit | Dane Peagler

[dpeagler]

Hello all,

I am in a circuits class now and we are doing our end of the year project. I have decided that I want to do some sort of circuit that counts things. For the actually counting portion of the circuit I am just busting open a cheap little calculator and connecting two leads to the = button so that if you type some numeral and operator before then you can just hit it and it increments this count.

In terms of what I want to count, I was thinking of adding some type of speaker to the circuit so that every time I clap, snap, yell, whatever it increments this circuit, but I have no idea how to do this. I am pretty sure that I will have to have some sort of transistor hooked up as an amplifier to the speaker so that it will create a large enough voltage to actually complete the circuit, but I have no idea besides that.

Thanks so much for any information at all.

Dane Peagler

 

[sparkey]

what kind of restrictions are on this project? is this on your bill or does your school have a decent size stock system?

is this a breadboard type project or a mount-all-your-junk-on-plywood type project?

 

[dpeagler]

Sorry, I guess I should have been more specific. The school is picking of the bill and has pretty much everything you can imagine. It is also on a bread board not a duct tape masterpiece.

 

[madmike159]

End of what year. Not sure quite what you want your circuit to do or how complex it needs to be.

 

[dpeagler]

This is just a project for the end of my circuits class. Nothing fancy just something the teacher gave out to try to stir up more interest into circuits.

I prefer it to not be complex at all. I would like for it to be as simple as it can be and still establish the task.

What I really wanted to do was to hook up some type of sound amplifier so that every time a noise of a certain amount of decibels the counter section of the circuit will increment by 1.

All I am going to do for the counter portion of the experiment is attach the 'equals' button on the calculator to the circuit so that when the circuit is completed or broken (not for sure which one has to happen) the count will increment. For example if you put '1' '+' and then '=' everytime you put '=' it will move the count up by 1.

So the main thing I'm confused about is how to tie the two together. Any suggestions?

 

[vk6kro]

The key switches on a calculator are part of a matrix of switches, so it is better to switch one button mechanically with an actual switch than to try to use a transistor to do it.

For this, you need a small relay.

The output of a microphone is very small. About 0.01 volts. So it will be necessary to amplify this small signal a lot until it is big enough to operate a relay.

Fortunately, this is a common thing that is done in radio transmitters.

It is called VOX. This type of circuit switches on a transmitter when someone talks into the microphone.

If you do a search on Google, you should find many circuits by searching for VOX.

An alternative if you just wanted to count something is to use a Hall Switch integrated circuit. These switch in the presence of a strong magnet.
So, you could have a magnet near one of these chips and it can be removed by someone opening a gate or a door. This causes a switching so that you can count how many times a door is opened.
A simpler amplifier would be required to do this than to use a microphone.

A calculator can probably only increment a count a few times a second, so applications like counting motor revolutions would probably not be possible as these rotate too fast.
I know you didn't ask this, but you should keep it in mind.