Design validation request

[frankpintosr]

Hello everyone!  I am working on a Raspberry Pi 3 Model B+ Carputer for my car.  I am a complete novice and wondering if someone would be kind enough to look at my design and validate for functionality.  I am most curious about the power circuit which comes from the car fuse block, to a voltage regulator and then to some buck modules.  I opted to supply power to some components directly from the buck and not the PI.  Will that cause any issues?  I have listed all my components below, almost everything from Amazon.  I would also appreciate any feedback or suggestions!  Thank you in advance!
   

Equipment - Amazon Shopping List
2004 Chevrolet Tahoe Z71 with Bose and Onstar
Raspberry Pi 3 Module B+
Offical Raspberry PI 7" Touchscreen LCD Display
GeeekPi Raspberry Pi 3 B+ Cooling Fan
Samsung 128GB EVO Plus Class 10 Micro SDXC (MB-MC128GA)
Coolwoo Backup Camera, 175º Wide Angle with 12 LED Night Vision Lights<
REDGO Video Audio VHS VCR USB Video Capture Card
HiLetgo DS3231 High Precision RTC
DIYmall 6M GPS Module with EEPROM with Antenna
UGREEN USB Audio Adapter External Stereo Sound Card
LANMU 48CM TF to Micro SD Extension Cable
eBerry USB Microphone
CHELINK 1.5M Universal Flush Mount Cable, USB & 3.5mm AUX Headphone Mount Flush Dash Panel Mount
WGCD KY-040 360 Degree Rotary Encoder Module
Blu Ray DVD Drive Burner Player USB3.0 Portable Slim Automatic Slot-Loading
AmazonBasics 4 Port USB 3.0 Hub with 5V/2.5A power adapter
Rii i8X 2.4GHz Mini Wireless Keyboard with Touchpad Mouse Combo
uxcell Power Converter Regulator Waterproof Voltage Convert Transformer
Moeye 12V Car Add-a-circuit Fuse Adapter
eBoot LM2596 DC to DC Buck Converter 3.0-40V to 1.5-35V Power Supply Step Down Module
Yeeco 4X50W Amplifier Board 4-Channel Car Audio Amplifier Digital Amp Board With Noise Reduction
PAC RP5-GM11 Radio Replacement Interface With Built-In OnStar Retention/Steering Wheel Control Retention/Navigation Outputs

[BlueWave]

Hi, these are our thoughts:

What is the idea of those DC-DC buck converters 5V-5V? Maybe you could remove them?
The same thing with 5-3.3 converter. You can connect the RTC directly to the RPI 3.3V
Do you need external GPS module? If you are not going to us it in some RPI apps or have no issues with your phone GPS quality signal then you could consider to remove it. 
If you have external sound card with aux in, there would be better to buy jack microphone, as they are cheaper.
Did you think how to handle shut down of the RPI in the car? 
Please have a look at others solutions:

https://bluewavestudio.io/community/showthread.php?tid=616
https://bluewavestudio.io/community/showthread.php?tid=673
https://bluewavestudio.io/community/show...hp?tid=810

[frankpintosr]

@bluewave Thank you for the reply! I am responding to your feedback and also sharing additional details with planned enhancements. Thank you for the input so far, I’m looking forward to any additional feedback too!
1.  With the buck converters I was trying to provide “clean” power and reduce the load on the Pi. But if there is no benefit then I can remove them. I have several future enhancements so I’m concerned about running out of Pi provided 5.5v and 3.3v pins.
2.  I use iPhone so no Android Auto for me. I also want my OA to be self contained so that’s why Im using an external GPS module. 
3.  I purchased the USB mic because I could not get the mic jack on my external sound card to work while using my iPhone to make calls. But the Mic was cheap, $7.99, and it worked immediately. 
4.  I haven’t selected a shutdown method yet. I was thinking of using four 18650 batteries as a type of UPS.  Then configure 2 sets of 2 batteries in series and then parallel.  This combined with the shutdown method. Which do you find the most reliable method? 

Upcoming additions
1.  FM radio module of some kind
2.  Rotary dials for volume and FM station tuning
3.  Ambient light sensor
4.  Front and passenger dash cam with DVR 
5.  Graceful shutdown with UPS capability 
6.  RP3 performance enhancements (SD CARD and GPU overclocked)

Future Additions
1.  I will be attempting adding steering wheel controls for volume, audio source on the Pi (mp3, FM radio, CD player), and change fm radio station
2.  ODB2 integration with dashboard display app
3.  Vehicle remote start
4.  Waze or other good navigation app
5.  Audible app
6.  Replace factory Bose amplifier with 5 channel amplifier (CH1 and CH2 Front speakers, CH3 and CH4 rear speakers, CH5 for subwoofer)
7.  Add DSP module
8.  External USB WLAN for internet

[BlueWave]

We have moved this Topic to 'Your projects' section, as this seems to be more adequate. 
In our opinion there is no need to use extra 'clean' power. The most important is current efficiency and voltage stabilization of your power supply.
As we wrote in another post, maybe you can check Waze for Rpi in case you are not able to use AA.
UPS is good solution, however it requires to be maintained by the user.  We prefer solution which does not require manipulation. As BWS CAR PS is not available, this alternative is quite interesting:
https://bluewavestudio.io/community/show...hp?tid=797

The FM radio is a long story: 

https://bluewavestudio.io/community/showthread.php?tid=682&pid=5041#pid5041

Currently, there is no need for performance enhancements, but it is up to you and your project. Just check CPU load and available memory.
The OBD support will be available soon in the OAP.
Other stuff sounds good and it is possible to be done.  Maybe 'Vehicle remote start' is more challenging, but why not.

[dreamvictim]

Hi, a little tip for your Mic not working with the USB sound card.

Most USB sound cards use a TRS socket but the majority of car Microphones have a TS jack. Try it without pushing the jack all the way in (leave approx 2mm of the jack exposed).