5v 1A Adafruit Power question

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supernoob
 
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5v 1A Adafruit Power question

Post by supernoob »

5V 1A (1000mA) USB port power supply
https://www.adafruit.com/products/501?g ... Ogod9F4AJQ

How stable is this power supply? Are there any specs I could see? If I'm using if for analog in for Teensy or Arduino with pots and ref things, I would like to know how much it will jump around.

Thank you for the help.

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Re: 5v 1A Adafruit Power question

Post by adafruit_support_bill »

These are quite stable and we use them for many projects. However, for critical voltage measurement, you don't want to use the same supply for powering your circuitry and as a voltage reference. Even if you are using an ultra-stiff lab-grade bench power supply, the switching transients from digital logic will create noise on the 5v rail of your Teensy or Arduino. We generally recommend using the 3.3v pin as a voltage reference since it tends to be somewhat quieter. For utmost precision, there are dedicated precision voltage reference chips.

http://www.linear.com/products/voltage_references

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supernoob
 
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Re: 5v 1A Adafruit Power question

Post by supernoob »

Great! Thank you for that link. That is exactly what I need. In choosing the correct voltage regulator for the Adafruit 5.25V USB POWER, I understand all the specs except the Current stuff. Could you help? Not sure how much minimum or maximum Teensy 3.1 input pins are looking for. And how much these voltage chips could put out. Say I was to choose the LT1790 would this circuit be how you use it to read a pot? See pic. And how many of these could I do before the LT1790 sees too much current load? Maybe you could explain the specs at the top of the pic.

Thanks!
voltage regulator.jpg
voltage regulator.jpg (101.59 KiB) Viewed 196 times

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Re: 5v 1A Adafruit Power question

Post by supernoob »

If I'm understanding input pins correctly they are very high-impedance and current draw will be very small here. So this circuit with the regulator will be ok?

Thank you for the help.

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Re: 5v 1A Adafruit Power question

Post by adafruit_support_bill »

You do not want to pull significant current from a voltage reference. That is not its purpose. Use the power supply to power your circuit. Use the voltage reference strictly as a stable voltage reference for analog measurements.

On the Arduino, you would set AREF to EXTERNAL http://arduino.cc/en/Reference/AnalogRe ... rence.AREF
and connect the output of your voltage reference to the AREF pin.

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