I keep reading your updates and it makes me keep putting off buying a new touch screen for my carpc....thanks mate.....on a lighter note i cannot stop reading.on the hum when the jeep is off and the amp is still running i got the same thing with my carpc.ended up doing the same thing as you.
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Another quick comment....the obd app.torque is fantastic and they have a free version and the paid is like $10 well worth it.just got onto the orux maps its one of the best i agree.im planning on using mine for 4x4 trip logs and mapping.
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thanks man! glad to know someone is reading some of this ;)
Originally Posted by camo.b
do you have a worklog?
Is been a good read mate .well done.ive got bits and pieces spread out over about 4 forums.i was going to do one but the wife complains enough now about my "me time".
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first major setback, getting rid of the after-startup noise turned out to be a huge hassle. in hindsight, i maybe should have just moved the entire support chassis further from the tablet. but i really didn't want to start running wires all over the place like my last car pc, and the nearest place it would fit was under the rear seat. so here's what i've done so far instead...
i found out the noises were definitely the 4G data connection. my phone radiates even worse, i could just hold it near the electronics and do anything to stream data and there was lots of EMI. the tablet at least only did it right when it first "enabled data connection".
with this knowledge, i figured i just needed some shielding - wrapping everything in any grounded metal box should act as a faraday cage. so off to make a metal box the right size. then it occurred to me to use the factory radio chasis, after all the radio's tape player was dead so it wasn't worth trying to sell.
taking apart the radio was a giant PITA, i could have built a box from scratch just as fast probably. most of the circuit boards are soldered to the chasis!
at least i found out why the tape player died, these were floating around in the bottom of the unit ;)
when i put together the new chasis, i also moved the line-driver to the rear (as far from the tablet as possible), and moved the bluetooth receiver away from the line-driver and power supply.
so after getting the main components into the new chasis, i tested it and the noises were significantly reduced, but not gone completely :(
so i changed the front mounting plate to a full 3/16" thick aluminum, added solid 1/8" plates to sides of the radio, and another solid plate to the bottom. i ran out of plate before i could do the top. with these changes, the noise has dropped a good 90%. i think once i plate the top it will be gone.
here is the nearly finished Chasis 2.0:
fitting everything in was like playing Tetris. i still have to make holes in the front plate for power & usb to the tablet, and then attach the tablet cradle again.
i inadvertently fixed my other minor hissing noise while doing all of this, so that's a bonus! this chasis is also waaaaay sturdier and i shouldn't need to worry about anything coming loose while offroading.
Might have been a PITA but it does look very tidy.
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- been working on my Tasker setup and the basic intelligence for car mode versus around-home or around-camp is there (including wake/sleep profiles in car mode), adding some little details now
- have also been evaluating/purchasing a few apps and widgets to improve the whole experience
- 99% noise free, still working on a last tiny bit of 4G related EMI
- tested on a couple short trips around town. i may need to replace the one piece of aluminum that connects the custom cradle to the chasis as it has a little flex. it doesn't bounce around, but when you press the far edges of the screen there's a little "give" to it and i'd like that to feel sturdy.
the software side is coming along (apps, Tasker config, UI customizations)...
the home screen is setup to display some info and give access to all the commonly needed functions:
i'm setting up Tasker so that the tablet is always in a "mode". the modes control things like screen brightness/timeout/lock, GPS/WiFi/4G/BlueTooth status, launch/kill apps, music stop/start, etc.
- "Default" is for normal around home or public use
- "Jeep" is for when docked and has sub-modes for awake, sleep, and hard-sleep
- "Trailside" is for the scenario of reviewing maps outside of the Jeep with other folks on a trip
whenever the tablet looses power (Jeep turns off or i remove it from the dock), i'm prompted for 10 seconds to change modes, otherwise it remains in "Jeep" mode but enters the "sleep" sub-mode. there will be more sub-modes for "Jeep" later (day/night, remote-manage, etc).
the lock screen is also setup to give me access to the modes. swiping to any mode icon unlocks and switches to that mode. the main unlock icon just unlocks and remains in the current mode. the lock screen isn't shown when the Jeep starts up, this is mainly for when in other portable modes.
- the backgrounds are photos i took of the Jeep and cleaned up in Photoshop.
- the icons all came from the app "MetroStation icon pack"
- i'm currently using the free version of Apex Launcher. CyanogenMod 10 has a new launcher (Trebuchet) and it's still got a few bugs. once 10.1 is stable for the XOOM, it sounds like it'll have all of the Launcher features that i want built-in.
- the weather widgets are from the app "HD Widgets"
- the music control widget is from the app "PlayerPro Music Player" (ICS theme for the widget and using Holo ICS theme in the app itself)
i thinking the PAC LD10 line driver may just be a POS...
- it's giving me amp thump during turn-off for sure. and i've found other reviews online with the same problem
- i think it may be of limited frequency range as my audio sounds "flattened" regardless of how i adjust the EQ on the tablet, and i've definitely lost my low end as compared to the factory head unit. this may be a limitation of the BlueTooth audio adapter instead, but i've read several reviews of this and similar cheaper line-drivers not being full range.
- it is the main source of my EMI noise. at first i figured any preamp was going to have the problem... however now that i've done some more research it seems there may be more sophisticated designs that will reject some of this noise.
i've ordered a JL Audio CL-RLC to try instead. it has the following features that i liked:
- a small form factor that will fit with existing system design
- has differential-balanced inputs. if i understand this correctly it may help fix the EMI noise introduced in the input cable coming from the BT audio adapter.
- rated >117 dB S/N ratio (compared to the LD10's 96db)
- lists a frequency response of 10Hz - 30kHz (LD10 does not even indicate it's range)
- has an external volume knob i can use temporarily while i work out my steering wheel control interface
my only concern is if the CL-RLC will be loud enough with the factory amp. it has less gain than the LD10, but a higher voltage (7.5V RMS) output... so we'll see.
wanted to say that the folks at mini-box.com (makers of the M3-ATX) are very helpful! instead of just telling me that i was using the product in a way that it wasn't designed, they offered me technical docs and we exchanged several emails.
i was able to use a USB-to-Serial adapter to program the M3-ATX power supply to behave almost exactly as i wanted. it now does a "hard-off" 5 seconds after ignition-off instead of just starting into a shutdown sequence designed for motherboards. i was also able to shorten the remote amp turn-on delay (anti-thump). the only thing it does not have the capability to do is provide a different amp turn-off time. my existing solution of using a relay to combine the anti-thump signal and the ignition-on state seems to work fine though.
if anyone else needs to program an M3-ATX via USB, you can use a cable like this one from SparkFun: https://www.sparkfun.com/products/9718
note that you can't directly connect that, you need some jumper wires like these to go with it (or hack into the serial cable from mini-box): https://www.sparkfun.com/products/9140
however, if you have the space, the M4-ATX supply is the simpler option as it comes with a USB interface and is still relatively small (and fanless).