I'm pretty new to Microcontrollers and I have mostly just a programming background. What I am trying to build is a device that uses the ultrasonic sensor to turn a LED on/off using the HC-05 bluetooth modules. EX: ultrasonic sensor says the distance is <= 20cm --> Slave LED = ON ultrasonic sensor says the distance is >= 20cm --> Slave LED = OFF

The board with the short circuiting problem is the Master device and the with the bluetooth connected LED is the slave. I keep having a problem where when I plug the Microcontroller into my Macbook Air with the USB, the board short circuits. I am not sure if I just need some extra hardware or if I am wiring some aspects wrong. I did some trouble shooting and figured out that the Microcontroller only short circuits when the a wire is plugged into 5v. This only happens with the Master device and not the slave device. It'd be really great if you guys could help me out. Please let me know if you'd like anymore information! Thank you!

P.S. On the sketch, the resistors go in order from left to right, 220 ohm, 1k ohm, and 2k ohm


  • The voltage divider at the HC-05's RX is wrong way round, though I don't think, that would cause a short. – chrisl Jun 26 at 7:13

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