Maximum number of supported leds?

In the middle of a Hackathon here guys and I want to convince my partner that the Particle Photon is the way to go here. I want to transmit a signal over the cloud to another Photon and have a servo turn on a coffee maker. I however would like to hook up 25 leds, yes 25. Can this be done or is this madness? Which type should we buy if it’s possible? The idea is to have a 5x5 matrix of lights that can be manipulated to create patterns using 7 outputs.

I don’t mind sourcing the power or whatever has to be done. I really think this would be cool.

Wish I didn’t see this :frowning:

If only I could pick it up at a store

The simple way to make a martix is to have one pin per row, and one pin per column.
A 5x5matrix then requires 10pins, you turn on 1 row at a time combined with the cols you want to show, by doing it fast enough it will look like they are turned on at the same time.

The downside is this requires some processing running all the time, but depending on what tasks the photon is otherwise doing that may be ok.

Or you can use a shift register (for example a 74HC595), these you clock a series of states into and then latch them, they can be daisy chained, so one 595 sends its data to the next 595.
That means you only need 3pins to control any number of LEDS, the downside being you dont get brightness control, its on or off.

Alternativly you can use smart LEDS, for example WS2812 / neopixels, these take a digital signal that defines color and brightness for each led, giving you full color control.

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@demented, you can also consider charlieplexing:

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Thanks for the ideas! Really appreciate the timely responses

Any reason for this? There are a plethora of online sellers which have some amazing things to play with. Worthile ordering some things. If you’ve got a small budget, China is always a great option :smile: Ebay often works too, although the cheapest things will still be from China.

I just wanted it by today for this hackathon haha. I am ordering some though!

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so consider making wiring and driving them easier with an I2C version… something like this.

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