All-in-one Boat/Car Arduino?

Hey all!

I've got a project to add Arduino Pro Mini to sailboat. Main purpose is to show information about battery/usage, voltage and current on a 16x2 LCD.

AND cut off the battery from all devices, if battery voltage is too low. Then bring it back after it.

Sailboat gets its power from small outboard engine to be used small times when leaving/arriving pier.
Solar panel charges the system as well as it can.

Load on the boat is about 5A max, and 1-3A average, depending on outside conditions.

All of this will be made on Eagle and ordered on a PCB, mainly for the learning and because its cool! This will be my first project on others than veroboard :slight_smile:

----- Ideas so far -----

Voltage divider of 100k/47k is used to measure battery voltage.
Current is analog output from ACS712-05 from ebay. (more of this later)
Fet to control Load line? No relay to save battery current. And takes a lot of space on pcb
Arduino Pro mini with headers to custom pcb

----- Questions -----

Are the ideas ok?
Because im working on custom pcb, it could be okay to add the ACS712-05 chip itself to the same pcb. No need for external pcb.s

What fets to use? Im thinking about using one output with 10k resitor to n-channel logic level fet. Which is connected to P-channel fet, with 10k resistor to source. Would it work? What to consider when switching the load?

And YES i do want to control highside(positive wire from battery)

Images does not include the acs712 on board, but it would easily fit between load and ground.

--

Feel free to comment. Images are not finished product. Traces on the pcb are just for clarifying what im about to.

Attaching a schema and a board layout to tell more than thousand words.


Heres an update about a raw sketch of schema with ACS712.
Some finetuning still going on. Also this is my first PCB with Eagle, so feel free to give advices.

So this is the newest version. Feedback required :slight_smile:

The electrical environment in boats with gasoline powered generators and automobiles can be extremely harsh for electronics, with the possibility of battery polarity reversals and voltage spikes greater than 100 volts. You will want to put some protection in place for these possibilities.

Be sure to do some research on this. One place to start is here.

I would skip the Arduino Pro Mini and just use an ATmega328P-PU (DIP) chip. It only needs a voltage regulator, bypass capacitors, and a pull-up for Reset.

The electrical environment in boats with gasoline powered generators and automobiles can be extremely harsh for electronics, with the possibility of battery polarity reversals and voltage spikes greater than 100 volts. You will want to put some protection in place for these possibilities.

Be sure to do some research on this. One place to start is here.

I might be that a 15V tvs-diode will be added. That should make it clear for spikes. Polarity reversal is not possible or a concern in this matter.

I would skip the Arduino Pro Mini and just use an ATmega328P-PU (DIP) chip. It only needs a voltage regulator, bypass capacitors, and a pull-up for Reset.

This came to my mind, and i even looked for ATmega328P-AU, but it would need iscp header to burn bootloader. DIP-case would take almost as much space, as Pro Mini. So Pro mini is better.

DIP is almost as long as Pro Mini, and i can place 8050 resistors under the Pro Mini.

Good advice anyway. But would i need reset button?

google watt meter