Small project #3 — IR controlled MOSFET with PWM


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This little thing is a variation of a previous project, but now with a majority of the parts in SMD packages. Needles to say it is also a lot smaller. The 2nd biggest difference is the added logic-level MOSFET that can be used a plain low-side switch, but also supports PWM. When I made this board I was thinking about remote controlling 12V LED strips, not the addressable kind, but the simple mono-colour ones that run all the LEDs in parallel. Fortunately, most of the code can be reused.

As far as the electronic side is concerned, there’s really not much going on:


The parts I like most about this little project are the MCP1804 (50µA standby current) and the cute little DPAK MOSFET, which packs a lot of punch for its size. The ATtiny85 has pissed me off quite a bit by not having a 150mil wide body. One could argue that I goofed up the footprint, but I choose to think otherwise ;-) I made it fit by bending its legs.

The first version of this board, shown in the images above, still came with a 7805-type voltage regulator, which was replaced by the MCP1804 (see schematic) and allowed me to shrink the board’s height by 2mm. The new voltage regulator shaves off a couple of mA of current consumption. The 7805 on the other hand is / was quite greedy.

The 2nd revision works too. I wish I had one I/O more to have the LED separate from the soft-uart. Further improvements to make: move the LED to the left side of the board, so it can’t get covered when bending the IR sensor over. Use a smaller resonator (Muratas CSTCE-G instead of CSTCEE). Make the board a bit smaller ;-)


As usual you can have all design files and code. Search for “LED-strip_PWM_IR” and take a look inside the “ATtiny_projects” repo for code: [1],[2].

You can find it on tindie!

Last build:


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