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### Topic: Talkbox project, what kind of speaker should I use? (Read 696 times)previous topic - next topic

#### Jimbo735

##### Feb 12, 2020, 08:32 pmLast Edit: Feb 12, 2020, 08:45 pm by Jimbo735
Hi everyone,

I'm working on a project which involves a mini talkbox.
I want to send a square wave using the tone library to a transistor which will supply the speaker with 5V from an arduino nano, or I could connect it to a 9V battery which I'm guessing might be slightly less stable with current. Should I use a 1 watt or 0.5 watt 8 Ohm speaker, and does the resistance matter if the speaker connects straight to ground? Does it affect how much current is required to make noise or just the current exiting from the negative?

Thanks!

#### DVDdoug

#1
##### Feb 12, 2020, 10:32 pm
Quote
I'm working on a project which involves a mini talkbox.
I want to send a square wave using the tone library
I don't know what a talkbox is, but is a square wave OK?

Power is Voltage x Current.
Current is Voltage/Resistance or impedance (Ohm's Law).

From that you can derive Power = Voltage2/R.

A "regular DC" square wave is off half the time so that's half the power, so if you calculate 9V2/8 Ohms = 10W so that's 5W into the speaker.   (With regular audio AC sine waves you get even less power from a given voltage.)

#### Grumpy_Mike

#2
##### Feb 12, 2020, 11:46 pm
Quote
and does the resistance matter if the speaker connects straight to ground?
How would it not matter. Ohms law says that for a given voltage as the resistance decreases the current increases.

Do not connect anything to the  9V  battery other than to regulator input. It will not change the output voltage. I have found that using a 33R speaker into a 120R resistor you can connect it directly to the Arduino pin providing it is always supplying a tone. If you want to stop the tone then make sure the output pin is set to zero or add a series capacitor to the speaker. It is plenty loud enough.

The power rating if the speaker is only the maximum power it will take, so for the tiny amounts of power here it does not matter. You get less than 0.2 W with this method.

#### Jimbo735

#3
##### Feb 13, 2020, 12:35 am
Sorry I thought the resistance value might've only applied after current ran through the speaker.

So I'd still be good to go if I use the 5V pin for power. Assuming the current from the pin is 400 mA I'd get around 0.25W so pretty much what you're saying.

What I'm trying to do is fit the speaker into a small container which leads to some flexible polytube which goes in the mouth of the user to talk over the square wave, kinda like what you here on Daft Punk songs (this kinda shows the same idea: https://youtu.be/NxF6FQA0hQs)
Would that be loud enough to make noise when the audio exits the person's mouth, similar to the video?

#### Grumpy_Mike

#4
##### Feb 13, 2020, 10:09 am
Quote
Sorry I thought the resistance value might've only applied after current ran through the speaker.
Now the word "after" shows you have not quite got how electricity works. Current flows through all parts of a serial circuit at the same time. It is a common beginners mistake to think it flows through one component and then the next. That leads to all sorts of misunderstandings.

Quote
So I'd still be good to go if I use the 5V pin for power. Assuming the current from the pin is 400 mA I'd get around 0.25W
No the maximum current you can draw from an Arduino pin is about 30mA at 40mA you start getting damage done to the pin. What do you mean by "5V pin for power"? For powering what.

That idea is called a talk box, I know you said so at the start but you used the term out of context. Here is a link for other readers about what you are trying to make
https://en.m.wikipedia.org/wiki/Talk_box
sorry no idea what sort of volume you need to use to make it work.

#### DVDdoug

#5
##### Feb 13, 2020, 05:42 pm
Quote
What I'm trying to do is fit the speaker into a small container which leads to some flexible polytube which goes in the mouth of the user to talk over the square wave, kinda like what you here on Daft Punk songs (this kinda shows the same idea: https://youtu.be/NxF6FQA0hQs)
Would that be loud enough to make noise when the audio exits the person's mouth, similar to the video?
I can't watch the video because I'm at work right now...

OK I know what that is, but I've only seen it used with an analog guitar-amplifier output, not a (boring) generated square wave.    And as far as I know the ones made for guitar effects are analog, and I don't see any need/advantage to digitizing.

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