How to make a 7x7 interactive platform?

Our project is to drive a toy car over the platform. Platform is consists of 49 squares , 7 on the edge of the platform. 7x7. Each square is 14x14cm and 3mm thick. They are rougly a couple of grams. Our goal is to use these squares as interactive tiles. Each square(tile) has a neopixel underneath. We are numbering these tiles from 1 to 49. For example, systems selects a tile. It will be lit green. And then toy car try to go over that green lit tile. So we need to know if that car is above that tile. To know that we need to scan and name each tile individualy. We are struggling with the system that detects the car. We are now trying to use buttons under each tile. But buttons are so hard to push that car will not push it while going above the tile. So we need a system that will be easy for car to push it while going above the tile. Also it needs to be cost effective. We considered using LDRs and buttons. We need different ideas.

Edit: We need to use maximum 3-4 digital pins for it. System will include other accessories.

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One possibility would be to use an RFID sticker tag on each square and put a reader under the car.

You could try with LDR matrix. You should read this:

Maybe it could help you.

I saw it, thanks. I will try that but I also need other alternatives. In case it doesn't work.

Suppose the car holds the knowledge of its position. Could blinking those LEDs in a code like "ROW COL" make the car know, and tell the system? Only the LEDs close to the current position would need to be blinking...
An exercise in microcomputer science, 1970:es, was to make a robot/car find its position scanning 3 IR lighthouses around the board....

Well if you had a bigger touch screen you can do it easy, You could find it on Alixpress for a few Dollars. You could buy a resistive or a capacitive screen and it used to use only 4 pins on your Arduino.

I guess it will be really hard for us to make.

Our platform is 1 metersquare. I don't think we can afford that size of a screen :sweat_smile:

Let the car have a 360 degree radiating item, IR, any light source... and 2 servo controlled light sensors triangulate the car from outside the board?

Reflective opto sensors under each square seeing a reflective surface under the car?

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yes and it isn't cheaper too... I think you could make a bigger LDR MATRIZ screen with an Arduino nano which you control your screen and translate it to 4 bits. Then with other arduino you do all your control system... maybe it could help you.

Ldr is worth trying but it also has issues. Like other light sources.

Does your platform have walls?
If so an echo location sensor on a 360 servo would allow you to discern distance. Combine that with an IR lantern in one corner and you can determine position as accurately as you'll need. This solution requires only simple math.
You'll need to use a small tube for the IR lantern and the receiver as rudimentary waveguides.

49 reed switches (7X7 matrix), magnet under car.

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Yes you could do a noise filter into your program for each input. Also, if you know about electronic calcs and teory you could make an active filter between your arduino inputs and your Matrix.

Please watch this regarding how to use a magnet with the reed switch.

Mounting the switches end on might be best.

That's really good. Cheap and also easy for us to build. We already know how to use multiple buttons from a single pin. With that we will only need to change buttons to these switches. Thank you a lot.

If you use an array of LEDs and multiplex them suitable they can function as both photodiodes and LEDs, allowing them to sense if a car's on top too. However the multiplexing is fairly complicated as you need full control of each LED for sensing as well as driving.