Clover’s Greenhouse update 4: Control Board

PARTS

1. perfboard

2. ribbon cable

3. 16 by 2 lcd

4. 10k potentiometer or patience and a resistor

5. female barrel jack

6. 7805 power regulator

7. (2) 10uF capacitors

8. Atmega 328 with arduino bootloader preloaded onto the chip

9. 28 pin dip socket

10. (7) 2-pin 5mm pitch screw terminals

11. (4) diodes

12. 22 gauge solid core wire

13. ftdi serial to usb break out board

14. 16 MHz crystal

15. (2) 22 pF (that’s picofarad not microfarad) capacitors

16. 100 nF capacitor

17. (4) 10k resistors

18. (11) female pin headers

19. (17) male pin headers

20. also, breadboards never hurt

 

SCHEMATICS

ASSEMBLY TIPS

Tip #1 : Breadboard before you solder! Make sure your parts can work before you melt them to metal.

Tip #2 : Go through the pictures and read the tags.

Tip #3 : I chose a large perfboard for this project because of all the external connections. Make sure you leave room in your layout for the LCD.

Tip #4 : Analog inputs are on the right. Digital outputs are on the left. I did this because the analog pins are all on the right of the atmega chip.

Tip #5 : Start with the power supply. This will determine where you place other components.

Tip #6 : While soldering the male headers to the LCD ribbon cable, keep them set in the female headers. This will prevent them twisting around in the heated plastic.

Tip #7 : While every component is important, the 100nF capacitor and 10k resistor coming from the reset pin (pin 1) are absolutely vital! Your board will not program without them!

Tip #8 : Connect the LCD wires on the back side of the board! It will save a lot of space and make it possible to examine your board for more than five seconds without losing normal human cognitive ability.

Tip #9 : This power jack will save you space. I got the large one for the sake of shipping costs.

 

PICTURES

4 Comments

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4 responses to “Clover’s Greenhouse update 4: Control Board

  1. Mike

    What are the specs of your relays? All relays I have worked with have too high of coil current requirements to power the coil directly from an arduino digital pin but your schematic says thats what you are doing. A common way to do this is control the coil with an N channel MOSFET.

  2. We thought of using a mosfet but I like the clicky noise you get from a relay. It lets me know everything is working. We used this 5 volt relay from sparkfun: http://www.sparkfun.com/products/100 It works perfectly.

    • Mike

      That relay says the coil current is 37.5mA. The atmega328 can produce 40mA on a digital pin, so I guess you are right in there!🙂

      Also, I just wanted to clarify, its common to use an N channel MOSFET to control the COIL of a relay (so you stil get the clicky noise from the actual relay). Many relays need 100mA or more on the coil to energize the relay. This is a common way to control a solenoid directly too, without going through the AC wall wart.

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