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PCB etched with toner transfer method
(lemmy.world)
This was my first try developing my own pcb with the toner transfer method. I did this project many years back but it works perfectly to this day.
It filters an audio signal and drives led strips so they pulsate to the beat of a song.
I just printed the design on a glossy paper and used an iron to transfer the toner from the paper onto the pcb (last image). The toner protects the underlying copper in the etching process, so only the free copper gets etched away. I used Na2S2O8 for etching.