General > General Technical Chat
29V Christmas lights: would like to mod with ESP32
<< < (3/3)
lezginka_kabardinka:
Done some reversing; what on earth is this biasing arrangement on the PNPs?

Edit:: oh, oh yeah of course, it’s setup so the bridge can be controlled with only two inputs from the MCU gpio:

When an input is high it turns on the NPN it’s attached to, and said NPN pulls the end of the 7k5 resistor connected to its collector to ground. therefore switching on the PNP on the opposite side of the bridge, thus both halves of that phase of the bridge (PNP & NPN) are fully on, and current flows from positive supply through the PNP, through the load, then through the NPN to ground.

Doh.
Zero999:
The NPN transistors turn on the PNP transistors.

Here's a simulation.

Note Q2 and Q4 mustn't be turned on simultaneously.
lezginka_kabardinka:

--- Quote from: Zero999 on December 24, 2023, 10:38:20 am ---The NPN transistors turn on the PNP transistors.

Here's a simulation.

Note Q2 and Q4 mustn't be turned on simultaneously.
[/quote

Gosh, thanks for knocking that up for me, brilliant! Happy Christmas, thanks for the help  :D
--- End quote ---
Navigation
Message Index
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod