Adding analog sensors with ADS1115
Michael Lane has been working on a new ADS1015/ADS1115 driver for reef-pi.
This brings new possibilities to Reef-Pi:
- PH/Orp probes
- Pressure sensors
- Flow sensors
- Etc.
Any analog sensor can be used as long as the analog signal is in between 2.0V to 5.5V.
ADS1115 16-Bit ADC - 4 Channel with Programmable Gain Amplifier
ADS1115 Features:
- Resolution: 16 Bits
- Programmable Sample Rate: 8 to 860 Samples/Second
- Power Supply/Logic Levels: 2.0V to 5.5V
- Low Current Consumption: Continuous Mode: Only 150µA Single-Shot Mode: Auto Shut-Down
- Internal Low-Drift Voltage Reference
- Internal Oscillator
- Internal PGA: up to x16
- I2C Interface: 4-Pin-Selectable Addresses
- Four Single-Ended or 2 Differential Inputs
- Programmable Comparator
I had an ADS1115 board so I tried if my PH probe is working. So I made a “How to guide” maybe it will be of use for others. I used a Raspberry Pi 2 Model B with Reef-Pi version 3.5.
Add driver under Configuration/Drivers
Configure the Driver:
Name: PH
Type: ads1115
Address: standard is 72
Gain: 2/3, 1, 2, 4, 8 or 16
An
Adafruit tutorial has this guidance.
# Choose a gain of 1 for reading voltages from 0 to 4.09V.
# Or pick a different gain to change the range of voltages that are read:
# - 2/3 = +/-6.144V (High Gain, Sensitive to noise)
# - 1 = +/-4.096V
# - 2 = +/-2.048V
# - 4 = +/-1.024V
# - 8 = +/-0.512V
# - 16 = +/-0.256V (Low Gain, Not Sensitive to Noise)
# See table 3 in the
ADS1015/ADS1115 datasheet for more info on gain.
Reboot (Configuration/Admin)
Add analog input under Configuration/Connectors
Configure the connector
Name: PHpin0
Pins: 0 (depends what pin you use on the ADS1115 board)
Driver: PH
Reload (Configuration/Admin)
Add the probe under pH
Configure the PH probe
Name: PH
Analog input: PHpin0
Check frequency: 10
Ph status: Enabled
The other settings are not mandatory.
Calibration
The first readings will be high:
Therefore you need to calibrate!
To be able to calibrate you first have to disable the Ph status
- Edit ph.
- Disable probe.
- Save
- Calibrate
- Rinse probe in rodi
- Place in 7 calibration fluid
- Wait for readings to stabilize
- Set cal value to 7 (Midpoint)
- Push Run
- Rinse probe
- Put in 10 calibration fluid
- Set cal value to 10 (Second Point)
- Run
- Enable probe
- Rinse probe and check both 7 and 10 and make sure it’s close.
Enjoy!