camdavids
Posts: 1
Joined: Sun Oct 07, 2018 12:59 pm

Dimming 200 Leds

Sun Oct 07, 2018 1:06 pm

Hi,

I have 200 5V LEDs, which each use about 5mW. I would like to be able to control all of them individually using a Raspberry Pi. I understand that I would need to use an external power supply (which I have), but I have been unable to work out what kind of components I need to use. Demultiplexers and shift registers both seem to be options, but all the advice I have found refers to arranging LEDs in a matrix and then scanning through it, which is not an option in my case.

I would ideally like to be able to vary the brightness of these LEDs, either by varying the voltage or by PWM (preferably PWM).

I would be extremely grateful for any advice.

Thanks

stevend
Posts: 203
Joined: Fri Oct 11, 2013 12:28 pm

Re: Dimming 200 Leds

Sun Oct 07, 2018 8:48 pm

There are a number of ICs around which are designed to drive a number of individual LEDs, complete with brightness control. These have either an SPI or an I2C interface, both of which can be driven from the Pi. You'll need to use multiple ICs.
SPI is potentially faster to complete an update, and, with suitable buffers, can drive reliably over longer distances than I2C.
Maxim do a range of devices for this type of interfacing.
Typical examples are MAX6956 (I2C) and MAX6957 (SPI); each chip can drive up to 28 LEDs (https://www.maximintegrated.com/en/prod ... X6956.html).
Worth looking at other manufacturers; TI (Texas Instruments), for example.

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