[Kosh]

I am currently in the design phase of building a circuit. Here is what it does. A keypad is connected to a circuit. The circuit is then connected to a speaker. If you push a number on the keypad, it makes its own sound. All of the numbers have their own sounds.


I heard that there was a kind of IC chip that I could use to do this. Of course it is possible that I need to use multiple ICs, this is acceptable. I do not know which ICs to use though, any ideas? Also keep in mind that these ICs need to be relatively common, since I don't have enough time to get one specially made.

[Grug]

- No freaking clue -

[Turnsky]

I am currently in the design phase of building a circuit. Here is what it does. A keypad is connected to a circuit. The circuit is then connected to a speaker. If you push a number on the keypad, it makes its own sound. All of the numbers have their own sounds.


I heard that there was a kind of IC chip that I could use to do this. Of course it is possible that I need to use multiple ICs, this is acceptable. I do not know which ICs to use though, any ideas? Also keep in mind that these ICs need to be relatively common, since I don't have enough time to get one specially made.

Flash Eproms i think are used in this case, Programmable IC chips, i've seen 'em around, and used them, that was years ago, however, and largely forgotten.

[Colonol Dekker]

Buy a cheapo keyboard, The office toy variety, palmsize and play around with it... see how it works

[Flipside]

If you were in the UK, I'd point you to Maplins....

www.maplin.co.uk

Theres just about anything the budding electronics guy could want in there

You might be able to at least get the component number from there

[Axem]

You could do it with a 555 timer and quite a few capacitors, or find an old phone and rip its DTMF stuff out

A quick search of DTMF Transmitter on Google turns up this: MT88L89. Its way more than you need, but it does have inputs for a keypad and output for your sounds. The only cavet with this guy is his odd voltage supply.

[Kosh]

I am trying to keep the circuit complexity down a bit, but also I need to be able to get this stuff off the shelf of an electronics store.


@ Flip: Maplins would be useful if I knew exactly what I needed (and if I lived in the UK), but I don't know what I will need nor do I live in the UK. Thanks anyway.

[Axem]

Well it sounds like you just need a DTMF transceiver, but I don't know if you can just pick it off the shelf. If you do find one on some electronics manufacturer's site, try to see if they give away free samples. I know a few companies do that, but shipping is usually pretty limited.

[Kosh]

Ok, so how do I use it? I've never heard of such a device......

[Axem]

Now that I think about it, it does get complicated. You'd need to get a crystal, turn the keypad's output into a 3 line input, and possibly amplify the transmitter's output.

Going back to my first idea, a 555 oscillator organ, this gives an idea on how to make one with different tones. All off the shelf stuff too.
http://www.design-technology.info/KS3/Y8/page9.htm

[Col. Fishguts]

Since I'm lazy, I would just use some cheap microcontroller. Hook your keypad buttons up to the inputs and connect an output to an amplifier. Then implement the functionality via programming the controller.

[Kosh]

So now I would need to totally re-learn assembly language too.........

[Bobboau]

I'd go the 555 route, you can get them at any local radioshack.

[Nuke]

transistors are your frirend

i remember when i was a kid i had one of those breadboards and some general components, it was a kit of sorts by which to learn the basics of electronics. there was this plan for a variable pitch buzzer which used a variable resistor to adjust the pitch. now it was simple, it used a transistor and a couple caps and the usual assortment of resistors. it was actually a very simple circuit. now you could use instead of a variable resistor, split the wires amongst all the keyswitches, and put different resistors at the other ind of each and re merge the wires. that way each time you hit a button, a different pathway is used with its own unique resistance.

[Descenterace]

It can be done with a hacked-up 4-bit DAC (resistors, plus transistors between keys and DAC inputs) and a comparator-based oscillator. I forget the details of the circuit, but the capacitor at the input of the comparator should have its ground connected to the DAC output. That'll adjust the oscillator period according to the DAC output.

[Kosh]

Since I'm lazy, I would just use some cheap microcontroller. Hook your keypad buttons up to the inputs and connect an output to an amplifier. Then implement the functionality via programming the controller.

I was thinking about doing this and it depends on if I can borrow the device to burn in the program. But I do have a question, how can the microcontroller output different sounds? I thought it could only output 1 or 0 (on the other hand it HAS been something like 4 years since I have worked with them).......

[Axem]

You could write a program that would cycle through 1 and 0 at the frequency you need, and hook the output pin to a speaker. And Viola, square wave generator.

[Colonol Dekker]

How complex did you wanna go with this build originally?

[Col. Fishguts]

I was thinking about doing this and it depends on if I can borrow the device to burn in the program. But I do have a question, how can the microcontroller output different sounds? I thought it could only output 1 or 0 (on the other hand it HAS been something like 4 years since I have worked with them).......

Well, yes, you can only output 0 and 1. So you could generate square waves, which you could smooth out by using some capacitors and resistors to form a lowpass.
On the other hand: In our last semester project, we used a MSP430 from Texas Instruments. Those controllers all have a digital part as well as an analogue part, with the appropriate A/D converters. While we didn't use the analogue part, I think you could use it to generate sine waves at your desired frequency. Btw, to program it, you only need the software kit (which has a 30 day free trial) and a cable to hook your boeard up to the serial port. Coding is done in simple C.

What are you doing, only a proof-of-concept prototype, or something for mass production ? Because the microcontroller approach surely is overkill regarding functionality and thus not fitting for mass production. But it's probably easier to implement.

[Kosh]

I'm just doing this because it has been far too long since I have done anything remotely like this. Like I said earlier, I haven't worked with micro-controllers in about 4 years or so. I also haven't touched anything related to circuitry in over a year. I want to do it to try and rebuild my severly rusted ECE skills.