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Has anybody built a BLM with bidirectional two lead duocolor LEDs, where the two colors can be adressed by reversing the polarity? How would the scan circuit have to be designed in order to work with the standard midibox solutions? Of course, compared with the scalar board, the resistor-transistor arrangement of IC2 could be placed next to IC3 and another 74HC595 next to IC2. But then the scan algorythm would also have to scan each color sequentially. Why am I looking for such a solution? I evaluated the the switch of choice for my Synth project: For my needs, I only have single color buttons (yellow). But this button could also be interesting for BLM applications where duocolor would be needed (RGB is available as well). I am working on a versatile matrix PCB solution for my synth project, where single rows of a matrix can be cut to the desired length and the LEDs can be adressed individually via solder jumpers. These smaller boards can be bought much cheaper in small quantities than the propriatary matrix boards and in my case serve different needs.

Hey guys I evaluated an LED backlit push button switch for my Synth project. Well Buying's TC011-A S4 T turned out to be the perfect switch for my needs: Although called tact switch, it feels more like a push button switch with a smooth pressure point and doesn't have the distinct click of a membrane switch. It's more like a Marquart but with a stronger spring resistance and a more defined switching point. The cap is 11x11 mm, translucent with a white diffusor cap inside (other versions with only square white caps are also available), as well as an ergonomic indent. There are different color options as well as duocolor and RGB available. Unfortunately, the duocolor version (colors can be chosen freely, as far as I know) is a bidirectional setup, where the LED has to be adressed by switching the polarity of the two leads. The switches can be obtained relatively cheap directly from the manufacturer Wellbuying from China. For a lot of 100 pcs, I paid only USD 0.78 a piece for a single color version. If anybody is interested, I can post pictures of the yellow as well as the orange version in action. I also have a contact, if somebody needs switches. Meanwhile, they are also available through Mouser, but for a much higher price. Find an individually addressable four button PCB eagle schematic for single LED type TC011s including the part library: LEDSwitch_Matrix_0.7_4.brd LEDSwitch_Matrix_0.7_4.lbr LEDSwitch_Matrix_0.7_4.sch Important: In case you want to use these PCBs in conjunction with a Schaeffer frontpanel with standoffs (no through hole), the mounting holes on the PCB need to be further apart as the glued on standoffs have quite a large base which otherwise interfer with the routed holes for the buttons.