Powering from breadboard power supply friend two Teensy LCs :(

[Jamewi]

I'm a bit devastated here... I killed two Teensy LCs and I have no idea how. Any guidance is appreciated.

I wanted to test powering the LC using a breadboard power supply. USB was disconnected (I have read the docs re: usb+external power), and I connected +5v and GND pins to a breadboard power supply. I powered on, and the LC is now dead.

I assumed I made a dumb mistake so I recreated the setup (raw fresh LC, breadboard power supply, no USB), and *POOF* instantly dead. Ouch this is getting expensive, and frustrating.

Both LCs were previously working.

On the 2 dead LCs I notice that now the 3.3v and GND pins are now shorted... what the heck happened to these things and how do I power the LC externally?

My wallet and my sanity thank you

 

[PhilB]

Without seeing how you wired it up, it's hard to tell. What did you connect to what.

 

[PaulS]

Too bad 2 LC's got killed...
Did you check the voltage and polarity of the breadboard powersupply? Is it really 5V? Absolute maximum voltage on the Vin pin is 6V.
Did you modify the LC's? That should not be necessary if you don't power them over USB.

Paul

 

[Jamewi]

Mystery partially solved; my 5v power supply is delivering 12v! It's a Robotdyn breadboard power supply and has jumpers to control voltage levels. 3.3v is working fine, but 5v is delivering 12v. I guess this is the price I pay for using cheap equipment during development. I am going to spare future teensies from this risk, get a reliable power source, and troubleshoot in a less destructive way.

I believe what happened is:

1. Something shorted somewhere and fried the power supply or the teensy or both at the same time. Power supply now destructively broken and teensy RIP.
2. Not realizing that the power supply is now in brain-eating-zombie mode, I tested on another LC and it fried.

Glad I didn't try any more!

Thanks for your responses.