Author Topic: When to use 1.1 volt v.s. 3 volt?  (Read 45 times)

kamloops

  • Newbie
  • *
  • Posts: 2
  • Karma: 0
    • View Profile
When to use 1.1 volt v.s. 3 volt?
« on: February 01, 2019, 06:43:59 pm »
First, I apologize if this has been covered or is so obvious that the question didn't need to be asked. I have googled the daylights out of this and can't find the info, so know I tried  ;D

My big question is, why and when would you would use the 1.1 volt v.s. the 3 volt sensor?

I currently have an Arduino UNO R3 with the inferior resistance-style sensors, but it has allowed me to get things going at least.

I have two sensors and two pumps running off of one Arduino and would like to keep it that way with the SoilWatch 10's if that's possible.

I am getting confused on whether I am restricted to either the 1.1 or the 3, or whether each offers different levels of sensitivity or other qualities, and whether you can run more than one sensor with the internal reference if using the aref on the board.

Can I just use the analog inputs with the 3volt version and be good to go?

Thanks in advance for any guidance you can give me before I order.

Cheers

« Last Edit: February 02, 2019, 04:19:53 pm by kamloops »

pinolec

  • Administrator
  • Jr. Member
  • *****
  • Posts: 63
  • Karma: 9
    • View Profile
Re: When to use 1.1 volt v.s. 3 volt?
« Reply #1 on: February 04, 2019, 08:30:12 am »
Hi,

This is a very good question.

Both sensors are the same construction and the only difference is the output range (0-1.1 and 0-3V). Both sensors read close to 0 in the air and close to 1.1V or 3V when submerged in water. The sensitivity is the same just in different range.
So when to choose 1.1V and when 3V. The first step is to check your ADC capabilities for maximum voltage. Some ADC allows the maximum voltage of 1.1V then 1.1V version is a good fit. Of course, you can achieve the same result by adding a voltage divider to the 3V version to bring it down to 1.1V.
When you power your device or development board form batteries or power supply is unstable then you will need a stable ADC voltage reference. Arduino UNO R3 offers a stable 1.1V internal reference. Then 1.1V version is well suited.

I assume you have you have a stable power supply so both versions will suit your needs.

Kind regards,
Piotr

kamloops

  • Newbie
  • *
  • Posts: 2
  • Karma: 0
    • View Profile
Re: When to use 1.1 volt v.s. 3 volt?
« Reply #2 on: February 04, 2019, 05:36:36 pm »
Thanks! This helps a lot. Nice to know that I’m good either way.

I finally figured out that the aref is actually an input for a custom voltage reference, which makes it much clearer for me now.

I will order soon and appreciate the help 👍

W