2 Channel Dimmer
The parts have arrived today to put together the first prototype of the 2 channel leading/trailing edge dimmer. The MCP4616A1T - SOT23-6 package IC from MicroChip is an I2C controlled 10 bit DAC. To have a diffferent address on the I2C network, you must order the appropriate model, so now I have address A0 and A1 DACS and can hopefully control 2 x FL5150 ICs from the same ESP8285 with the same control ciruit power supply. IFFF it does work then it should be possible to continue on with little trouble with a 4 channel dimmer as well.
These like the first model will be installed in a DIN mount enclosure.
See the video on an early prototype here:
This particular DAC can be used to control the FL5150, as the output of the DAC is an op-amp and can regulate the required voltage at the DIM control pin, which sources or supplies current. This means that the DIM control pin if connected to GND via a 200Kohm will essentially sit at 2.6V full brightness, but as the resistance is reduced the the voltage at the DIM Control pin reduces and so does the brightness. The OP-amp inside the DAC does the same job however we can set the voltage arbitarily with our ESP8285 to hgive us the required light level.
The FL5150 if you look at the datasheets, essentially in most of the examples is powered buy a bridge rectifier formed in part by the MOSFETS, and 1 or 2 additional diodes, a resistor to reduce current flow and a zener inside the IC. So basicly its a shunt power supply and it gets hot all the time. I can tell you from experience that it can not be powered by a a simple non-isolated power supply, I can't tell you why it doesn't work and have not yet found an explaination. But it will work with a isolated power supply.
I'm keen to see how to will operate with 2 DACs and 2 dimmers on the same 12v isolated supply. Lets find out...