research:automated_chicken_door

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Automated Chicken Door

Automating the opening and closing of the chickens door reduces the mental payload and gives more freedom. It also makes the chickens more safe as humans might forget to close the door in the evening.

This is the very definition of progress: making life easier.

Solution Price Plus Minus
12V timer ~10€ Easy to set up, reliable Setup has to be changed over the year ; 12V powering needed ; Power consumption ?
Arduino mini + electronics ~8€ If battery/solar powered, the board has to be modified to reduce the power consumption ; Electronic circuit has to be built and programmed
Analog electronics ~5€ Low power Electronic circuit has to be built
Solution Price Plus Minus
Electric car antenna ~20€ Easy to integrate
Winch actuating a sash ~10€ Can be built with broken electronics Has to be built
Servo-actuated self-locking door ~10€ Complex to build
Solution Price Plus Minus
Solar panels ~5€ Energy self-sufficient ; Coop easy to displace Requires low power electronics
Power adapter ~5€ Stability Requires a power line
Rechargeable Battery ~15€ Coop easy to displace Inconvenient ; Requires low power electronics

As we try to reuse the tings we have and to buy as less as possible, the solution depends a lot on the material already available.

Function Selected solution Why
Controller Analog electronics low power, low cost
Actuator Winch actuating a sash no cost because reused materials
Power Solar panels we can reuse solar lightings for garden, can be moved, energy self-sufficient

The total cost will only be around 5€ for the electronics. The drawback to this is the time demanding construction work.

If the system is powered by a battery or a solar panel, an energy analysis can be done to be sure of the feasibility, or to be able to improve the design.

Energy used by the motor

Parameters we need to know:

Current measured through motor while door is lifted I_motor = 100mA
Voltage powering the motor V_motor = 6V
Time measured to open T_open_door = 10s

First we calculate the power drawn from the motor:

P_motor = V_motor * I_motor = 6V * 100mA = 600mW = 0.6W

Then we can calculate the energy used by the motor to open the door:

E_open_door = P_motor * T_open_door = 0.6W * 10s = 6W.s

This energy can be converted in W.h:

E_open_door = 6W.s = 6/3600 W.h = 1.6mW.h

As the door needs to be closed as well, we just double this value to get an approximation of the total energy used by the motor per day.

E_motor_per_day = 2 * E_open_door = 3.2mW.h

Energy used by the electronics

The electronic component consuming most of the energy is the Op-Amp. A calculation could show that the power consumed by the other components is negligible. Indeed, we try to use resistors having high values.

Below is a graph from its datasheet showing the power supply current. We can see that it is about 1.2mA at 6V.

Power consumed by the Op-Amp:

P_oa = V_oa * I_oa = 6V * 1.2mA = 7.4mW

Energy used by the Op-Amp per day:

E_oa_per_day = P_oa * 24h = 7.4mW * 24h = 0.177W.h

We can see that it is much more than the energy used by the motor. While the motor consumes 100 times more power than the Op-Amp, it is used only 20s a day, while the Op-Amp is always on.

Energy available per day

The solar garden lighting give approximately 4h of light every night. From this information, we can estimate the energy available per day.

The LED is powered with 1.2V and consumes 30mA. We can measure this with a multimeter.

P_led = V_led * I_led = 1.2V * 30mA = 36mW
E_led_per_day = P_led * 4h = 36mW. 4h = 144mW.h

The batteries of the garden lighting have a voltage of 1.2V (can be read on the package). As we want to power our system with about 6V, we have to use 5 garden lightings, and to connect their batteries in series.

E_available_per_day = 5 * E_led_per_day = 144mW.h * 5 = 720mW.h

Conclusion

Summary:

E_motor_per_day 3.2mW.h
E_oa_per_day 177mW.h
E_used_per_day 180mW.h
E_available_per_day 720mW.h

We are happy to see that more energy is available than used. The security margin tells us that after one normal sunny day, the system can work without additional energy for 3 more days.

Security_margin = E_available_per_day / E_used_per_day = 720mW.h / 180mW.h = 4

For improved performance, we need to use a low power Op-Amp (such as TLC3702CP)

  • research/automated_chicken_door.1497386072.txt.gz
  • Last modified: 2017/06/13 22:34
  • by florent