Fish Feeder Project

This project is remix of “Automatic Fish Feeder with micro servo control V2” by Paulo Cunha.

I have slightly modified some parts, redesigned hopper, added base part and control box.
Initially I used original design with mixer inside hopper powered by spur gear. However, flake food was jammed in hopper sometimes and mixer did not help to prevent such situations. Therefore I have removed horizontal mixed and added much bigger vertical mixer powered by additional servo motor. After two months of operation it seems to be quite reliable.

Video: https://youtu.be/azTHyCNVLFo

Electronics is based on ATTiny841 chip programmed in Arduino IDE. Main goal was to keep power consumption low. The cpu is mostly in sleep mode, there is no display. Operation is triggered by real-time clock module DS3231. Powered by a single 18650 Li-ion Rechargeable Battery.

I have selected ATTiny841 because it had integrated hardware serial interface. It is used for setting time, alarms, etc. I did not use Arduino Mini etc. because I had to create pcb board for other components anyway so I included cpu there. By other components I mean n-channel mosfet switches mainly.

Two 9G servo motors are used – modified to work as a DC motor (removed electronics and connected directly to motor, cracked potentiometer to allow free rotation)

Features:
• precise real-time clock
• two independent programmable alarms (feeds) in a day
• programmable via serial link
• adjustable time duration for auger and mixer servo (separately)
• button for instant feed (out of alarm time)
• buttons for adjusting feed servo run duration
• indication of low battery voltage

Electronics
Electronics is quite simple – ATTiny 841 controls servo motors via two n-channel mosfet switches. RTC board and Li-ion charger board are available at ebay.com:

RTC DS3231
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.XIIC+Precision+RTC+Real+Time+Clock+Memory+Module++DS3231+AT24C32.TRS0&_nkw=IIC+Precision+RTC+Real+Time+Clock+Memory+Module++DS3231+AT24C32&_sacat=0

CHARGER
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.XMini+USB+Lithium+Battery+Charging+Board.TRS0&_nkw=Mini+USB+Lithium+Battery+Charging+Board&_sacat=0

Detailed description in attached pdf file.
Source Arduino, Eagle, Inventor files are attached too.