@NeverDie Thx for appreciating the work done. There will also be an open source part in the future. When and how extensive the open source part will be, remains to be seen. The release of certain information (block diagram, ..., in this post) is related to those open source parts.
There are some OBD solutions, however most of them (in my experience) give back low frequency data put by the car manufacturer on the OBD-bus (CAN, ...). Therefore transients evolving directly from the battery could only be recorded if the manufacturer sends those data accordingly on the bus. Due to the small bandwidth(also because of other car data that have to be sent, ...), such battery data are sent more often once per second or less. Fast battery events (i.e. cranking events, ...) are therefore imperceptible. Unless the manufacturer processes the fast events and then sends them (once per second or less), which is very unlikely if the manufacturer does not market this feature itself. Third parties devices for high frequency sensing costs several hundreds dollars.
In my experience, important battery states (especially the fast ones) are recorded by measuring and processing corresponding data directly on the battery.
I agree with you about the limits related to the communication over Bluetooth. But i think Bluetooth 5.0 will improve a lot. However, WiFi will always remain an important option due to the high data throughput. The combination of both (BLE & WiFi), especially with regard to energy consumption, will gain in importance.
This is a simple, low-cost and quick project that can get a high spouse acceptance factor.
Remove the led strip from the aluminum profiles.
Cut the aluminum profiles and the covers to appropriate length. I used a hacksaw to cut profile+cover at the same time to ensure the got the same length.
Cut the led strips at one of the cut points using a side cutter.
Remove the old wires (they are too short to reach the box) and solder new wires.
Put the led strip back inside the aluminum profile. Note that there is a small grove at the back for the strip, this ensures that the strip is close to the profile to maximize cooling.
Glue the profiles to the mirror. I used slow-curing epoxy.
Drill holes in the project box for the switch (6mm) and the potentiometer (6mm should be enough but was too tight so I used 8mm).
Drill a 4mm hole for the wires to the led strips.
Upload the sketch to the Arduino
Connect the Arduino and the battery packs and put them inside the project box.
Fasten the project box using double-sided tape.
Big thanks to my wife for letting me use the action photo.
The choice of MOSFET can be tricky. Seems that irlz44n was discontinued so you may need to find one adapted to the voltage and current you want to handle.
In all the cases you need to get a logic MOSFET too, meaning that they are fully open usually around 1 to 3V.
Also I'm sort of confused as it seems to me that L7812CV is a Voltage regulator, not a MOSFET. So if you are actually using that in the MOSFET spot it will definitively not work.
Especially if you are handling high current or voltage I would recommend using one from a reputable source for your MOSFET, I recently switched from mouser / digikey / aliexpress to mostly use http://www.arrow.com as you get free regular shipping, event if you order a couple of components (no affiliation to them whatsoever).
Im not sure where you get that #9 should be A5? Looks right to me. The pin is connected to pin 9, and that is D3.
For a rotary encoder, it depends on your input - but don't you want an analog signal in? In that case you use the analog pins.
Edit: offcourse, if you use a module converting it to digital like described in the the build section you use a digital pin.
@victus Im not familiar with this components you mention, you need to test yourself, cant help you with the technical stuff.
It does not seem to be a fully functional ECG but a heart rate monitor. As epierre said above, you need to define if you want to monitor or have a fully functional ECG, its a big difference. With a monitor all you get is pretty much your heartrate and you can detect arytmias. A fully working ECG is normally made with 12 leads and is used to in detail know how the electrical depolarisation from different time and direction/place within the heart muscle works. Holter is a example of a heart rate monitor over time.