3 different power sources

P

peeddrroo

Member
Hi

I have a question regarding power :
I am building a MIDI controller and I want to connect it in 3 different ways : USB, MIDI and Ethernet
My idea is to use a Teensy and a Bome Box, which has Power Over Ethernet.

I will have 3 different options to power the Teensy :
- from the USB when connected to the Bome Box's POE
- from the USB itself when no Ethernet cable is connected to the Bome Box
- from an external power supply (9V lowered to 5V)


how can I implement that and make sure I am not going to damage the Teensy ?
 
peeddrroo said:
Hi

I have a question regarding power :
I am building a MIDI controller and I want to connect it in 3 different ways : USB, MIDI and Ethernet
My idea is to use a Teensy and a Bome Box, which has Power Over Ethernet.

I will have 3 different options to power the Teensy :
- from the USB when connected to the Bome Box's POE
- from the USB itself when no Ethernet cable is connected to the Bome Box
- from an external power supply (9V lowered to 5V)


how can I implement that and make sure I am not going to damage the Teensy ?
Click to expand...

Which Teensy?
Are you making a pcb?
 
I plan on using a Teensy LC as I need 5V output for LEDs.
Yes, I'm making a PCB.
I have drawn a little sketch of the connections.
The red lines show cables providing power.

The 9v power supply won't always be connected, neither will the ethernet or the USB, so I need to provide power with any of those.
The 2 USBs won't be connected at the same time.

I guess my question comes down to : Is there a way to provide power to the Teensy via an external source and still be able to power it with the USB without using a switch ?
Capture d’écran 2022-05-30 à 08.56.57.png
 
peeddrroo said:
I guess my question comes down to : Is there a way to provide power to the Teensy via an external source and still be able to power it with the USB without using a switch ?
Click to expand...

You could cut the VUSB-VIN pads apart. Then on your PCB, connect a diode from VUSB to VIN(5V). And from your 5V regulator (Teensy LC can't run directly from 9V) use another diode from regulator output to VIN.


BriComp said:
You realise that the LC is NOT 5V tolerant.
Click to expand...

The normal pins aren't 5V outputs or 5V tolerant, but the special output connected to pin 17 is a 5 volt buffered output.

But the buffer chip is powered by the VIN pin. If VIN has diodes between it and the actual 5V power, it will probably get about 4.3V with normal diodes or 4.5V with schottky diodes. Maybe that's still ok for the LEDs?
 
You must log in or register to reply here.
Back
Top