Is 36 inputs possible?

Using Arduino Project Guidance
#1

Can an Arduino handle 36 inputs?

I want to make a Learning (?) Board for my son that has 36 individual buttons (A-Z and 0-9) which will play unique and specific *.mp3 files (recordings of mom or dad saying each letter/number). Is this possible?

I would imagine that the easy answer is to use several Arduinos, but I'm also looking to use what I already have without the expense of buying more boards.

Thanks for any advice you can give!

#2

We don’t know what Arduino you have.

You can use i/o expansion I.C.s

You can use a Mega.

#3

For an Uno, you can use I2C exanders (MCP23008, MCP23017*, PCF8574) or parallel in-serial out shift registers (74HC165) get over 100 inputs.

*or the SPI MCP23s17.

#4

You can connect the buttons as a matrix, 6 lines by 6 rows. Usual technic for some keyboards.

#5

larryd:
We don’t know what Arduino you have.

True, thanks... I have the UNO. Circa 2011 (?) It's old.

#6

Hi,

Easiest and probably cheapest these days is an Arduino Mega which has 48 digital signal pins.

To make it not-as-insane to wire, get a Mega Sensor Shield (LINK)

1024×596 360 KB

and use ribbon cables to connect to your many switches. See THIS PAGE

Like these:

1024×368 71 KB

Then if needed cut of the ends and solder to you switches..

#7

Railroader:
You can connect the buttons as a matrix, 6 lines by 6 rows. Usual technic for some keyboards.

I thought about this, but (and please forgive the ignorance) wouldn't that matrix result in every line being grounded to itself?

#8

Here is a playground page on the basics of matrix keypads.

#9

Actually, don’t fart around with expansion chips.

Terry offers very reasonable boards.
Mega @ $18.00
Digital I/O Pins 54 (of which 14 provide PWM output)
Analog Input Pins 16

#10

@deafmike,

Where in the World are you?

If you promise to write your whole project up and include photos of The Kid using it so I can put it on https://ArduinoInfo.Info I'll send you a Mega and Sensor Shield...

I have 14 grandchildren and am a sucker for KidsFunStuff :slight_smile:

#11

The solution suggested by groundFungus needs 6 output and 6 inputs, a technicaly easy solution.

#12

Multiple buttons with resistor ladders on analogue inputs is another solution.
But a keypad matrix should be easier.
Leo..

#13