Real-World Tests and fixed i2c communication

A project log for DIN Rail 10 channel LED PWM Dimmer

Use 10 channels of PWM dimming in an electric cabinet over Ethernet with the power of an ESP32

Patrik MayerPatrik Mayer 12/04/2019 at 16:152 Comments

Just wanted to give you guys a short update.

We've finally found an homer-like flaw (doh) in the i2c communication to the PCA9685. Some idiot (me) forgot to tie the address lines of the PCA to ground properly. So in some raw situations the chip decided to change it's I2C address while communicating, thus resulting in kernel panic's on the ESP32 side.

After fixing this, handling the ESP32 exceptions better, refining the I2C pull-up's and meassuring the i2c bus for stability, we could move on to our first real-world test. Currently we drive up to 40 channels with 24V LED's with four dimmers over UDP without any problem.

We've built a custom mqtt-adaptor to talk to the dimmer via node-red and get some status information back to display it on a dashboard.
This functionality will be integrated into the dimmer itself as soon as whe have time to implement it. All different communication path's (UDP, HTTP, MQTT) will be selectable from the dimmer's webinterface.

Currently the speed parameter is not working so well - next step here is to implement propper timing to be able to use miliseconds for this parameters.
The different dimming curves look stunning with smoth transitions, of course depending on the LED's.

For a test we've also built to run on the hardware - worked after getting the configuration right, as the output enable of the PCA9685 is wired to a GPIO.

I'll leave you guys with a photo :-)
Feel free comment in any way.



Emanuele Tessore wrote 01/08/2020 at 09:06 point

Hello Patrik, 

how many Amps\Watts?
With or without heatsinks on FETs?

+1 for the "hello there" silkscreen :)


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Patrik Mayer wrote 01/08/2020 at 10:06 point

We have planned the traces for 24V/8Amps per Channel. But this is too much regarding heat - also keep in mind, that the dimmers are typically mounted in a closed cabinet.
We've successfully had 6A on all 10 channels over night and went not over 45°C on the FET's. But this was an ohmic load, not a LED (capacitive). So I think 24V/5A shoulb be good... maybe don't exceed 24V/40A on all channels combined.

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