0

ADABOX003 - power for OLED, PIR?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

ADABOX003 - power for OLED, PIR?

by Ebottis on Sun May 14, 2017 12:16 pm

Hi, i would like to connect the OLED and the PIR (eventually replacing the PIR with a a break beam I just ordered) to the feather to send data to io.adafruit. What is the best way to power the PIR? It requires 5V for best performance but I can only pull 3 off of the feather, right? I would like to run this off of one USB power supply if possible.

Ebottis
 
Posts: 8
Joined: Fri May 12, 2017 1:01 pm

Re: ADABOX003 - power for OLED, PIR?

by adafruit_support_mike on Mon May 15, 2017 1:15 am

You can get 5v power from the Feather's 'USB' pin as long as a USB cable is connected.

You might need a level shifter on the output to make sure that's 3.3v-safe though. Feather logic is 3.3v-only.

adafruit_support_mike
 
Posts: 45246
Joined: Thu Feb 11, 2010 2:51 pm

Re: ADABOX003 - power for OLED, PIR?

by Ebottis on Mon May 15, 2017 10:43 pm

Thank you - I am pretty new to this. Can you point me to level shifter resources? Thanks again!

Ebottis
 
Posts: 8
Joined: Fri May 12, 2017 1:01 pm

Re: ADABOX003 - power for OLED, PIR?

by adafruit_support_mike on Tue May 16, 2017 12:01 am

A buffer like the 74LVC245 is probably easiest to use:

https://www.adafruit.com/product/735

The LVC family is designed to work as what's called 'glue logic' between 3.3v and 5v systems. The input pins can handle 5v while the chip is powered from 3.3v, and the output is safely in the 3.3v range.

adafruit_support_mike
 
Posts: 45246
Joined: Thu Feb 11, 2010 2:51 pm

Re: ADABOX003 - power for OLED, PIR?

by Quantum_Star on Mon Jul 24, 2017 6:53 pm

I was working with the Feather and a PIR sensor, and I ended up just hooking the positive power of the circuit to the USB pin of the Feather. This worked when powered by the USB port, but not so well when powered by a battery. I discovered that you can actually set up the PIR sensor to work with 3.3v! Apparently, the internal voltage for the PIR is 3.3v anyway, and it uses a voltage regulator. By soldering a wire to the middle and bottom pin shown in the pic (or just the bottom pin, but it's really small, and it's a lot easier to connect the two and then attach the wire to the bridge).

Here is the original post that pointed me in the right direction: http://randomnerdtutorials.com/modifyin ... k-at-3-3v/

There also seems to be PIR sensors that have a jumper which you can draw 3.3v from, the HC-SR501: https://www.youtube.com/watch?v=5jhTQAV ... e=youtu.be

Quantum_Star
 
Posts: 12
Joined: Fri Sep 16, 2016 5:32 pm

Please be positive and constructive with your questions and comments.