My In-Dash Nexus 7 Project

by **nickknack** » Wed Jul 10, 2013 8:46 pm

Hey guys, I currently have a slight ground loop/alternator whine coming through with my nexus install. SQ is fine with the car off, but you can notice it when driving. My setup is Nexus 7 -> USB DAC(fostex PC100-USB) -> RCAs ->3.5mm adaptor -> Ground loop isolator -> 3.5mm input of my HU. Can anyone offer any ideas?

This is my head unit: http://www.jvc.com.au/car-av/head-units/kd-r736bt

Would an RCA to usb adaptor plugged into the usb input fix it?

by **su34ru** » Wed Jul 10, 2013 9:52 pm

seanmau5 wrote:Looks reasonable. Do you just unplug it and take it with you when you leave the car?

At the moment, yes.
But I did pull apart the fascia today to look at the possibility of pushing the stock HU back an inch or two (as suggested by Statts) and mounting the Nexus in dash. There isn't an awful lot of room behind the stock HU unfortunately. But this is based on a quick check. Will do some further investigation over the coming days.

by **su34ru** » Wed Jul 10, 2013 10:36 pm

Statts wrote:If you want to go really basic and try your luck, then grab one of these. The problem I saw with this is with cranking the engine, accessory power is cut in some cars, or drops very low due to massive draw from the starter motor. With the DCDC-USB you are dealing with a proper power supply, that will survive this cranking state and provide uninterrupted power. The power drop will mess with mounted external HDDs as they will drop out and cause an "unsafely removed" error, which will only be cleared by a reboot. If you never plan to use an external HDD for media storage, you may get away without a decent power supply.

Hi Statts
Question for you reg the power supply - did you actually have trouble with the cheap ebay ones, or did you just decide to get the Rolls Royce

of power supplies?
I ask as the price difference is significant and it it tempting to try the $7 variety before plunging into $95 territory.

Having said that, I have a Belkin Bluetooth to aux device connected to the Cigarette lighter socket which always turns off with the engine crank. I assume the power cuts off for a bit (or if I'm lucky, it drops low rather than cut out altogether). Would the DCDC-USB ( I will be tapping in line the cig lighter power) still be able to provide uninterrupted power in this situation? Why would the ebay variety not be able to do so?

by **seanmau5** » Wed Jul 10, 2013 11:21 pm

The cigarette lighter wouldn't be your constant 12v, you could use it as the accessory (or trigger if you like).

On turnover most of the battery's power is drawn to the starter to crank the engine over and ignite, I'm led to understand that the DCDC will provide an uninterrupted supply.

As for the eBay version, I too wondered this. I am embarking on the tablet install and $100 for the power supply is definitely harsh! Guinea pig the cheaper version for us??

by **pgardiye** » Thu Jul 11, 2013 6:38 am

I'm using this one from ebay - http://www.ebay.com.au/itm/waterproof-DC-DC-Converter-Regulator-12V-Step-down-to-5V-3A-microusb-female-usb-/171070011910? and no issues with power. Btw I don't have a usb hub to power, simply using dc-dc adapter to power nexus and my blueant bluetooth. I have 1tb external hard disk connected to nexus and charging seems to be going pretty good so far.

btw I have connected this to car cigarette lighter...

by **Statts** » Thu Jul 11, 2013 8:10 am

nickknack wrote:Hey guys, I currently have a slight ground loop/alternator whine coming through with my nexus install. SQ is fine with the car off, but you can notice it when driving. My setup is Nexus 7 -> USB DAC(fostex PC100-USB) -> RCAs ->3.5mm adaptor -> Ground loop isolator -> 3.5mm input of my HU. Can anyone offer any ideas?

This is my head unit: http://www.jvc.com.au/car-av/head-units/kd-r736bt

Would an RCA to usb adaptor plugged into the usb input fix it?

I'd be looking at the quality of Earth connection to your power supply and your headunit.

su34ru wrote:Hi Statts
Question for you reg the power supply - did you actually have trouble with the cheap ebay ones, or did you just decide to get the Rolls Royce of power supplies?
I ask as the price difference is significant and it it tempting to try the $7 variety before plunging into $95 territory.

Having said that, I have a Belkin Bluetooth to aux device connected to the Cigarette lighter socket which always turns off with the engine crank. I assume the power cuts off for a bit (or if I'm lucky, it drops low rather than cut out altogether). Would the DCDC-USB ( I will be tapping in line the cig lighter power) still be able to provide uninterrupted power in this situation? Why would the ebay variety not be able to do so?

I personally didn't try the cheaper power supplies, but many over at RootzWiki in the thread for USB-ROM did have troubles ranging from charging slower than discharging, dropping out during cranking (can especially be a problem for those using a DAC (if DAC drops power during crank, it may not be detected on when it gets power again)) and ground loop noise. Other great features for the DCDC-USB include a switched aux output (think for turning amplifiers on in stand-alone installations) and the ability to tweak the output voltage (Upping to 5.4v means an awesome charge rate).

As Sean said, cig lighter will only be used for 12v trigger, with constant power pulled from elsewhere. The circuitry in the DCDC-USB is robust enough to continue power supply even when the 12v trigger goes low during cranking.

by **Robbks** » Thu Jul 11, 2013 9:02 am

ACC power goes fully to ground when cranking not just low voltage.
You need IGN power if you want uninterrupted power.

by **Slate** » Thu Jul 11, 2013 1:23 pm

Been looking for some kind of cheaper Alternative to the FSL -21 with no luck...

Has any one else done any better?

Alternatively maybe a group buy is in order?

by **su34ru** » Thu Jul 11, 2013 4:33 pm

seanmau5 wrote:The cigarette lighter wouldn't be your constant 12v, you could use it as the accessory (or trigger if you like).

On turnover most of the battery's power is drawn to the starter to crank the engine over and ignite, I'm led to understand that the DCDC will provide an uninterrupted supply.

As for the eBay version, I too wondered this. I am embarking on the tablet install and $100 for the power supply is definitely harsh! Guinea pig the cheaper version for us??

I would've guinea pigged but seems pgardiye beat me to it!
I am going to give this cheapie a try.

Pgardiye - can you confirm you have no issues with power loss during ignition?

by **seanmau5** » Thu Jul 11, 2013 6:10 pm

I would like to try a cheapie but I'm also running a DAC, 1TB hard drive and possibly a DVB TV tuner at a later stage, so a quality reliable power source is what I need.

Speaking of my set up; you happy to help out Chris? I'm happy to wire you $250 if that's enough to source what I need?

by **Statts** » Thu Jul 11, 2013 9:38 pm

seanmau5 wrote:I would like to try a cheapie but I'm also running a DAC, 1TB hard drive and possibly a DVB TV tuner at a later stage, so a quality reliable power source is what I need.

Speaking of my set up; you happy to help out Chris? I'm happy to wire you $250 if that's enough to source what I need?

As mentioned in PM, more than happy to help. We'll discuss it there.

by **pgardiye** » Fri Jul 12, 2013 10:59 pm

sorry for the late reply guys, i have no issues with the dc-dc adapter during ignition. Even if you have little power drop, usb rom will try going to sleep and abort as soon as power being restored. I don't have a DAC or USB hub, my setup is pretty simple with a 1TB hard disk.

su34ru wrote:
seanmau5 wrote:The cigarette lighter wouldn't be your constant 12v, you could use it as the accessory (or trigger if you like).

On turnover most of the battery's power is drawn to the starter to crank the engine over and ignite, I'm led to understand that the DCDC will provide an uninterrupted supply.

As for the eBay version, I too wondered this. I am embarking on the tablet install and $100 for the power supply is definitely harsh! Guinea pig the cheaper version for us??

I would've guinea pigged but seems pgardiye beat me to it!
I am going to give this cheapie a try.

Pgardiye - can you confirm you have no issues with power loss during ignition?

by **su34ru** » Sat Jul 13, 2013 1:45 am

pgardiye wrote:sorry for the late reply guys, i have no issues with the dc-dc adapter during ignition. Even if you have little power drop, usb rom will try going to sleep and abort as soon as power being restored. I don't have a DAC or USB hub, my setup is pretty simple with a 1TB hard disk.

Ah... That explains it. The DAC will be the issue here. Statts had mentioned this earlier and I have now experienced this even with my basic portable setup using a portable charger to power the whole lot. Need to spend the $$ on power it would seem!

by **BlackSTI** » Sun Jul 14, 2013 8:36 pm

Parts are all inbound for my installation, I hopefully will have them by next weekend to start the installation.

I had a play today with trying to create an interface for my homescreen, I think i'll end up changing the background and finding a better font (as well as a now playing widget). What does your homescreen look like currently statts? or anyone else, trying to get some ideas on what else I could do.

by **Slate** » Tue Jul 16, 2013 12:59 pm

Hi gents,
Really excited about all this so I thought I'd post where I'm at,

I'm about 60% of the way through

Flashed the Nexus and have installed it into the car
(Based North of Brisbane and have finally mastered flashing so if any one needs some help, give me a yell)

Modded the Nexus as I didn't want to drill holes into my vents as I couldn't figure out how to lay out the wires to not interfere with the air con fins

Ended up opening up the nexus and lifting up the battery as well as the copper(may need to be revised) plate to reveal the ribbon cable for the power and 3.5
(inspiration from this guy on Youtube doing an install)

If you imagine on that last picture that the backing closed like a book, the bit where the ribbon cable crosses has been filed down on the back casing so that it can drop out underneath the nexus and hang.

at the moment its fixed to the casing that I used to mount the tablet to the car with double sided tape so that it's a little more secure but can still be removed when needed

So at the moment I'm running the 3.5 from the tablet to the 3.5 in my centre console and I have a otg y cable with nothing attached to the usb port connecting to the power of the cig lighter

dc dc usb is being shipped as we speak and the fsl21 is on the to do list.

One question some one may be able to answer is in the USB Host menu (pic below- sorry for glare) when I try to select Fixed instalation mode it "ticks" but if I close settings and open it up again it has unchecked itself. I was hoping that would be resolved with the OTG Y but I put that in this morning and nothing. so power source perhaps?

How's everyone else going?