Changing power source on Cerb40

I just got my order of USB to TTL gadgets in ( and I want to switch from using onboard USB to power my Cerb40 to using my TTL to USB module for “external” power. It seems obvious that I have to take off the regulator I installed, but do I need to take off the capacitor as well?

You just need to connect 3.3V and ground to the proper pads on the Cerb40. You can leave the regulator and capacitor. This assumes that you do not have a USB client connection while powering externally. If you want both, then you will need to remove the regulator.

I doubt his USB board has 3.3v so you will need to get USB voltage to the regulator on cerb40.

Actually, it ((Retired, replaced by PL2303TA) PL2303HX USB-UART Serial Programmer - ElectroDragon) does. I could also connect the 5v to the pad “USB”, bottom right on back of Cerb40, is what you are saying, right Gus? If I use the 3.3v provided by the USB board, and sInce I want to be able to debug while connected to the TTL converter, I’ll have to remove the regulator. So, with 3.3v “external” applied, and using the USB client connection for debugging, need I remove the capacitor in addition to the regulator?

In production, I will not be putting a regulator and cap on the Cerb, so I’d like to use the 3.3v supplied by the Prolific chip on the USB board in development also. However, development started with a regulator and cap while I waited for the USB board. Guess I’ll remove both just to be safe. It was just such an accomplishment to get that little cap soldered on with my big, clumsy hands.

That 3.3v is there to be used by the chip itself. I doubt it is good to power anything usefull.

I’d recommend using the 5V from the adapter, and keeping the regulator, since the 3V3 is unlikely to be capable of supplying much current.