Sensor Breakout Boards on 3.3V Controller
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Sensor Breakout Boards on 3.3V Controller

by IpsissimusMarr on Wed Jan 30, 2013 1:11 pm

I have switched to using a Teensy3 for my current project which is a 3.3V ARM MCU. However I want to use several sensor breakout boards from Adafruit that have 5V-3.3V regulators and/or shifting built-in:

ADXL345 Accelerometer
LSM303 - Accelerometer / Magnetometer
L3GD20 - Gyro
BMP085 - Barometric
Ultimate GPS

My question is whether the 5V-3V circuitry poses any unnecessary noise or other issues when used with a 3.3V MCU? Is there a simple way of converting these to strictly 3.3v boards? Is that necessary?

Thank you.
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Re: Sensor Breakout Boards on 3.3V Controller

by adafruit_support_bill on Wed Jan 30, 2013 5:28 pm

Just connect 3.3v power to the "3v3" pin instead of the "VCC" pin. That will bypass the regulator.
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Re: Sensor Breakout Boards on 3.3V Controller

by IpsissimusMarr on Wed Jan 30, 2013 5:49 pm

Oh, wonderful, I misunderstood the board layouts. I thought Vin took up to 5V and the 3V3 pin was the output of the regulator to use as an AREF on some of the breakout boards. If I can bypass the regulator that's perfect.

Looking closely at the image of the PCB for the ADXL345, LSM303 I see the 3V3 pin bypasses the regulator. But on the L3GD20 and BMP085 there is only a 3Vout with no bypass, correct?

Thank you for the quick response.
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Re: Sensor Breakout Boards on 3.3V Controller

by adafruit_support_bill on Wed Jan 30, 2013 6:06 pm

The 3v3 pin is connected to the output of the regulator on all of them. If you do not connect 5v to the input, you can power the breakout from the 3.3v pin.
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Re: Sensor Breakout Boards on 3.3V Controller

by adafruit on Thu Jan 31, 2013 11:46 pm

its an ultra-low drop out, you can always just connect 3.3v to the VIN (5V) pin and that will work fine
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