Thermistor with ADS1115 + voltage question

ESPHome
1

Hi all,

In a past project (How I added a Hayward solar pool control to HA via ESPhome) I basically tapped into an existing setup with thermistors so I could add the temperature of my pool in HA.

I’m now working on a new and upgraded setup in which I basically want to replace that solar controller with a different setup based on an ESP32-S3 and reuse those same thermistors. The board I already have (I’m using this one: WAVESHARE-6CH-RELAY | devices.esphome.io because of the multiple relays and RS-485 - there isn’t a fritzing for it but the concept is the same).

So I drew up a new approach:

ASD1115_board_bb
ASD1115_board_bb795×737 114 KB

Now, my questions:

  • will this work? I’ve not yet bought the ADS1115s so wanted an export opinion first :slight_smile:
  • the thermistors are 10Kohm but the tech sheet I found (for the Hayward solar controller - see below) provides measurements of resistance vs temperature using a 5V source - does this mean I should use 5V as well to have similar results? I know these are resistors and I think voltage doesn’t really matter but wanted to ask anyway. As the wires are quite long (ground to second-floor roof) perhaps 5V is better?

This is an extract of the Hayward resistance table:

Hayward_ohm_table
Hayward_ohm_table317×796 51.3 KB

Any advice anybody can give would be brilliant!

Thanks,
B.

2

I don’t see any reason to bring 5V to this setup.
If you don’t have ADS yet, why don’t you use the money for digital temp sensor, DS18B20 for example?

3

Thanks for the quick reply - will leave it at 3.3V then - it’s easier anyway :slight_smile:

From the layout of the board, does that look good?

I need to go for the ADS as I already have the sensors, one in the pipe of the pump inlet and one on the roof. As I need both temps to then open the valve so water goes to the roof.

4

Good enough…

image
image647×625 68.7 KB

Just simply wire them in single ended mode to ADS, one thermistor to A0 and second thermistor similar way to A1.

On esphome:
Use A0_GND and A2_GND
and
gain: 2.048.

If you measure some particular temp range, you can tinker with the gain.