LCD, 12V Boost, and controller

Alright, what I'm trying to do is combine the following:

  1. arduino board with atmega168a chip stripped down to the bare minimum running on internal clock.
  2. lm2731 boost converter. battery input 6-12V with 12VDC output.
  3. chip on glass serial lcd display

In addition I'll need to add a few transistors, switches, etc. and lines out. I'm controlling 12V solenoid valves (yes, read the tutorial). The thing is, I need to combine all into a 1"x2" one sided board. SMD is what I'm going for but preferably not so tiny as to be impossible to solder by hand. The LCD screen will be mounted on the back side of the board. The whole board would be at 3V per the lcd screen.

I've gotten as far as pulling up an eagle schematic for the lm2731 and my transistors etc, but I'm not sure how to proceed with integrating that with the arduino components. I'm afraid I'll throw out connections/parts that I need if I just start hacking it up and trying to combine them.

I'm hoping to program this with arduino ide and use the serial package to communicate with the lcd.

Any advice or help with how to proceed would be VERY much appreciated...I'm stuck.

Alright, here’s what I have. There’s still one capacitor and a few tactiles that need to be added, but it’s almost all there. this is the first board I’ve ever laid out, so any feedback would be great. Since I can’t do an internal ground plane with free eagle, I tried to keep the ground as low impedance as possible especially around the boost circuit. I’ve also pulled out all the SPI pins so that I can bootload the chip insitu. programming will then be accomplished by hooking up to mini usb adapter.

Am I correct in understanding that if I’m using the internal pullup resistor I don’t need any resistors on my input tactile switches?


Control Board.brd (128 KB)

Control Board.sch (402 KB)

I found a mistake I believe, I have the Vcc pin from the USB connected directly into the VCC for my chip. Only problem is I want the board to run at 3.3 to be compatible with the screen, not at five. I guess I need to tie the USB power in with RAW then so I don't fry my display.

I’ve attached the updated files with the following changes.

  1. Diode on RAW for reverse Polarity
  2. diode on both solenoid lines
  3. Added 3 tactile input switches on back (display side) of board
  4. Connected capacitor between pins 8 and 9 on display
  5. connected 5V from USB to RAW in order to regulate to 3.3V

Maybe a couple other things, but those are the main ones. Thank you in advance for taking the time to look at this.

Control Board.brd (135 KB)

Control Board.sch (407 KB)