Cable and Fuses For In Car Entertainment

[JonnyAlpha]

Hi;

I am building an In Car Entertainment and Technology System to install in a recently completed restoration project and need some advice with the wiring and fuses etc. I need to confirm the correct gauge for the wire and fuse ratings to ensure that everything is powered correctly and is adequately protected. I need to confirm:

(a) What size fuses and where to fit them (I have been doing lots of research).

and

(b) What gauge wiring between each piece of the system.

Details of the setup are as follows:

Setup

I am running a Raspberry Pi 3 which has an official Raspberry Pi 7 Inch attached to it. The screen is configured to get its power from the Raspberry Pi's GPIO and the Pi is powered by a Mausberry 3A car Switch details here:

3A Car Supply / Switch – Mausberry Circuits

The Mausberry is a 3A Switch which I guess means it can supply up to 3 Amps, it is also fitted with 18 Gauge wiring.

Attached to the Pi's GPIO is a pHAT DAC which will be connected via an RCA to 3.5mm Audio into an Aux In on a Sony CDX-GT26 Radio. The Radio is fitted with a 10 Amp Fuse (alternatively I have a Pioneer which has a 15 Amp Fuse)

Wiring and Fuses

I intend to run some 18 Gauge wire from the solenoid or an existing constant 12v supply and also 18 Gauge from a switched 12v supply with a fuse on each within 12 inches of their respective sources.

These 18 Gauge cables will run to a distribution point from where separate 18 Gauge 12v constant and switched cables will run to the Sony Radio and the Mausberry 3A Switch. I was planning on fitting additional in line fuses between the distribution point and the Radio and the Mausberry Switch (a 10 Amp Fuse to the radio (in addition to its on board 10 Amp fuse)) Or 15 Amp if using the Pioneer Head Unit (and a fuse to the Mausberry Switch (not sure it this should be 3 or 2Amp? Probably 2 or lower).

A pic of what I think I need is here (but the fuse for the Mausberry needs to be lower):

You can find the blog I am compiling on the build here: https://picodeandchips.wordpress.com/2016/11/24/featured-content/

Click to read more...

 

[wingless]

Welcome to the forum!

Nice diagram!

This link has tables showing the relationship between round trip wire length, wire gauge and current. Use the 3% voltage drop table.

When I do wiring I always bump up one size thicker.

Locate the fuse less than a foot from the power source.

It is possible to eliminate the first fuses if the Sony and the switch fuses / wires are run to the source.

The switch link does not show the recommended fuses. Follow the manufacturer's documentation for fusing.

Here is the Sony CDX-GT26 Installation Manual. They do not specify recommended fusing.

My guess is that both devices draw a small amount of current from the switched DC supply and draw most of the current from the continuous 12 VDC supply.

 

[JonnyAlpha]

Thanks for the help, I had been shown a similar wiring chart for 3% loss. The round trip I suppose refers to the length of wiring from the battery to the component (the radio) and back to the battery via Gnd? If I my ground point is on the bulkhead of the car and the battery in this case is in the boot do I include this distance?

For a 15 Amp circuit on a round trip of 10 feet the chart suggests using 14 AWG cable?

 

[JohnKuthe]

Thanks for the help, I had been shown a similar wiring chart for 3% loss. The round trip I suppose refers to the length of wiring from the battery to the component (the radio) and back to the battery via Gnd? If I my ground point is on the bulkhead of the car and the battery in this case is in the boot do I include this distance?
For a 15 Amp circuit on a round trip of 10 feet the chart suggests using 14 AWG cable?

And you CAN use even larger AWG cables for even less loss, but after a certain popint the gain you get from larger wires stops making "stellar" improvements (point of diminishing returns!)

John Kuthe,..