Vermes
Advanced Member level 4
There are few professional pH-meters available, which allow to measure the pH in aquarium and control the CO2 electrovalve. It's an alternative solution to these expensive devices.
Assumptions
- continuous pH measurement – range from 4 to 7 pH
- control of the CO2 electrovalve powered by 12V – keeping the constant level of both CO2 and pH
- program calibration of the device
- saving the settings in non-volatile eeprom memory
- simplicity of construction
- cooperating with Hydromet ERH-AQ1 probe
- alarm signaling by sound
The main element is Atmega168 – inside 8MHz. A signal from pH probe is pre-processed by TL074 operational amplifier, then given to the input of analogue-digital Atmega converter. Software in processor memory is responsible for the rest of measurement. The circuit was mounted on a one-sided board, in thermal transfer method with use of traditional hole elements. The board was sized for Z29 case. It enables mounting of this device in hanging position on aquarium cover or on a wall near the aquarium.
The device is powered by 12V power supply. It has to have an adequate current efficiency to the electrovalve operated.
The device communicates with its user by LCD display 2x16 marks. A keyboard with four buttons is used to make the settings. The program was written in C.
The device performs the following functions:
- continuous pH measurement
- control of the CO2 electrovalve
- alarm about too low or too high pH
- three LCD backlight work modes: always on, always off, extinction after 30 seconds
- settings saved in eeprom memory
- program calibration of the probe in model pH buffers
Link to original thread (useful attachments) – Ph-metr do akwarium - kontrola CO2
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