Animal RFID Tag Reader

My friend Nikita has a sheep farm. Some time ago we discussed together how we could increase efficiency in farm management. Some simple technological solution that can simplify work.

I decided to build a simple RFID ear tag reader, because inventory with piece of paper and pencil can by quite difficult with the number of sheep around 300. (live sheep tracking maybe later.)

Requirements:

- as simple as possible 

- bluetooth connectivity

- display easy readable on direct sunlight

- microSD card slot

I designed a simple PCB in stack with eink display. There is MCU, battery charger, battery protection, voltage regulator at the top of the PCB and BT module, microSD card slot and RTC at the bottom. The entire stack is enclosed in 3D printed case. 

RFID reader is simple RFID module from AliExpress. It has UART output and requires 5V power supply. I tuned the antenna to 137,5 kHz with capacitor on the module. Whole module is enclosed into 3D printed cover and will be placed at the top of the stick. 

Device is powered by 1s2p li-ion 18650 cell, which is located in handle. 

And all assembled together

The sheep must have an ear tag in both ears. Type of tags (RFID or classic) is optional for domestic breeding. On the photo: round in right ear - RFID tag, rectangle in left ear - classic tag 

At the end some photos and video from testing:

I am looking forward to the android application that Nikita is developing.

Here is the source code if you are interested.

Car handsfree

My car is older but I still don't miss anything about it. The only thing I miss is a hands-free phone.

My idea was to connect the mobile phone via 3,5mm jack to the small PCB, which split the audio signal into two. One for the microphone located in the interior light, other one for aux input on the radio. The PCB should also be equipped with electronics that will allow me to control the mobile phone.

I started with some small reverse engineering. 

I was looking for a message on the CAN bus indicating, that the buttons on the steering wheel were pressed. I found it with ID 0x5c1 and length 1 byte.

I designed PCB with jack connectors, relays simulating buttons and MCU STM32F072. 

Board is integrated into box and it is connected to radio, microphone, CAN bus and power supply. 

The board continuously monitors the can message 0x5c1. If I press top left button on steering wheel, relay on PCB is switched on. If I release button, relay is switch off. I use only function A, which allows me to control music playback in addition to receiving calls.

Wood chip burner

 My father dreams of heating the house with wood chips. He asked me for help in the development and construction of a burner that will fit his boiler. He had an idea of a burner that would not need any control unit and would work automatically (he was watching some videos on Youtube). 

I made some quick sketch in Solidworks and then start cutting and welding. 

The wood chip is in the tray and with gravity falls directly into the fireplace. Burning chamber is is lined with fireclay. 

This construction works fine, but it has some disadvantages. The worst of them is that the combustion chamber is outside the boiler. 

It's time to make another version. 

Nipple drinker for rabbit with heater

Anyone who keeps rabbits, quickly discovers, that water bowls are not the solution. The water gets dirty really quickly. (Sometimes it takes only few seconds. 😁) Nipple drinker is a solution. However, it has one problem, it freezes easily in winter. That's why decided to make a heating. 

System consist of 3 main part. 

- Main unit

- Heated nipple drinker

- Air thermometer with radiation shield

 

Air thermometer with radiation shield

One of the requirements, was energy saving. The heating should only be switched on, if the temperature id low enough. Air thermometer is small board witch LDOs, CAN transceiver, STM32F302 and temperature sensor SI7051. Of course, there is a status LED next to RJ45 connector. I didn't draw the radiation shield, I downloaded it and printed it out. I just drew new sensor holder, to fit RJ45 connector with the board. 

During testing I found, that using LDO was a bad idea. LDO heating up the board and this resulted in wrong temperature. I have to add small switch, which connect air thermometer to power supply every 2 minutes only for 2,5 seconds. After this modification temperature was correct. 

Heated nipple drinker

Drinker is made from IKEA food box. There is a heating element with floating switch and thermometer at the bottom. There is, of course, electronic board at the top of box. heating element is made from aluminum heatsink to which is attached aluminum PCB with SMD resistor and reed switch. The board is covered with epoxy to ensure waterproofness. On heater element is attached with screws floater with magnet. If the water level drops, the floater with magnet approaches the reed switch and heating is turned off. 

Heater element is attached to the holder together with thermometer.

 Thermometer is simple thermistor, but board is ready for 3 types of temperature sensor: analog thermistor, I2C, and 1-wire senor (maybe there will be some upgrade in the future). Board has STM32F302 microcontroller and also uses CAN interface. Each board has a header to set the CAN ID with jumpers. 

Main unit

Main unit is plastic box with 24V power source, IO RJ45 connectors, main board, display and some relays for disconnecting drinkers. I used the old sensor board again as the main board. 

I use CAN for communication between main unit, heaters and air thermometer. If air temperature is fall below 0.4°C relay connect drinker to 24V and starts heating them to 5°C (with hysteresis +-1°C). If air temperature rise over 1°C, relay is turned off and display show message "VYHRIEVANIE VYPNUTÉ" (heating off). During heating, display shows the temperatures of individual drinker. If the drinker is currently heating, a big dot will appear on the display. Drinkers send temperature over CAN every 2 seconds. If some drinker does not send message within 30 seconds, display show "ODPOJENE" (disconnected). 

I also made a simple RJ45 HUB that connects the RJ45 connectors together. 

GitHub

Cat litter box - net redesign

Unexpectedly, my cousin has heavy cats.

I designed a new 3D printed net. It's optimized for print on Prusa MINI 3D printer. It consist of 4 part. Back, front and two identical middle parts. 

New source data is here.