Keypad playing sounds - Recommendation for design

Thread Starter


Joined Aug 14, 2019
Hello everyone!
This is my first message in this forum and I really appreciate your help.

I want to design a gadget for my uncle who can not speak, just move her fingers. As I don't have an electronic profile (i am software developer), I am asking you for assistance in order to design the best cost-effective solution for this idea

Functionality: A keypad (colorful) that can play sounds associated with their own keys.

*Speaker - Q1. As the gadget probably will go on a wheelchair, it should be a rectangle (not too high). Where can I find it? Q2. What are the main characteristics of a speaker? What potency? Vats?. It has to be enough strong to let her communicate in the street. I do not know how to measure it.
*Mp3 player - Q3. Is it required? or maybe it has to be integrated with the PCB/microprocessor?
*Microproccesor/PCB - Q4. I know abut raspberry, elegoo and Arduino. However, I think these are overpowered for the simple functionallity to receive an order from the keyboard and play a sound. Maybe they consume more energy? What is your recommendation for this component?
*Keyboard - Q5 It has to be something like a matrix keypad but with color in the keys. I have not found anything on aliexpress related to a full matrix 3x3 or 4x4 with colors. I have found only normal keyboards with numbers. Maybe buy the keys separately and with their custom color?
*Battery. A thin battery. Q6. Will you design using standard batteries or use external battery than can be recharged with energy/power. Q7. What power is required for this design taking into account the gadget should be located on the arm of the wheelchair (it can not be so big).
*Case. Q8. Would you buy a standard box case and after receive it make some customization to place the keyboard and the battery connection charger? Q9. If it is a custom case, where will you get it? I will design it using SketchUp or some software in order to send it someplace.

Additional questions:
Q10. Is it my design correctly? Or will you recommend something else? A new better design idea?
Q11. Any cheap place to buy those components if I have to buy it for more people (to make between 30-50 gadgets for the nursing home)?
Q12. What is the cost per component you estimated?

Thank you a lot! Feel free to ask whatever you want.


Joined Mar 10, 2018
Are you trying to play stored speech ?

Some thoughts -

1) Keypad use CapSense and membrane overlay for colors.

2) Processor with DAC, OpAmps to power earbuds, and ability to interface with SDCARD (to store wavetable sound), a PSOC possibility.
It can also do the CapSense.

3) Speaker possibility to use

Board possibilities ( $ 4 to $10 in single units, use a 4M board since it will
debug, then final one of the $4 bootloader boards)

The above is a page for the PSOC 4M as well as PSOC 4 boards, latter being low cost bootloader

SDCARD projects

IDE and compiler free. PSOC Creator.

Regards, Dana.
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Joined Apr 11, 2010
With all the features that you want, I don’t think that an Arduino Uno R3 is overpowered.

Plus, take a look at this shield, SparkFun Music Maker MP3 player with Amplifier. It has a micro SD card slot. Thus, you can record specific words or phrases that you’d like played for a specific key/key combination.

The shield has a built in amplifier. SparkFun also sells compatible 4Ω speakers. (Speakers are rated in Watts and Ωs).

You are not limited to matrix keypads. I’d consider touch switches covered with thin vinyl for the colors. The wiring for a switch matrix is not impossible and in this manner your keypad can be anything you’d like. There are touch switch modules that will turn almost anything into a touch switch.

As far as power, I’d check out the model airplane RC market. I’d buy a lithium rechargeable pack and charger. You’ll need somewhere between 6V and 9V.

As far as the case, you’re right. You can use a standard case or 3D print a custom case. Search for “custom 3D printing”. I noted that UPS offers 3D printing at some of its stores. Note that the free version of SketchUp can’t produce files for 3D printing. You need a professional version. Or design it and get a friendly person with a pro or shop license to create the .STL files necessary for 3D printing.


Joined Oct 2, 2009
Welcome to AAC!

You certainly have posted many questions to which we can provide answers and suggestions.
Some are major (significant) and others are minor (cosmetic). Let's just tackle a few at a time.

1) What is the purpose of the device?
a) to play personal music?
b) to play recorded sounds such as speech and requests - as in communication assistive device?

We can discuss the speaker, battery, controller, case, design, etc., in more detail once we know the purpose of the device.

As for keyboard, it is not difficult to design your own 4x4 keypad with your own graphics overlay. You can use off-the-self matrix keypads and add your overlay. You can also build a keypad with dome contacts. You may also want to consider a touch sensitive LCD screen which will allow for total flexibility, multiple functions, and dynamic menu selection. It is worthwhile to think outside the box.


Joined Sep 17, 2013
Various sound record/playback modules are advertised online. Perhaps you could incorporate one or more of those in your project.