Finally going to do it!
I'm finally building the carpc I've wanted to build for 5 years!
It's going to go into a 2006 Crown Vic Police Interceptor. I intend to use ride runner, and I'm building as much as I can from "scratch".
I'll be using an Acer Aspire One as the PC, and I've got an old slide-out single din VGA touchscreen I'll be using for the monitor (If I didn't already have this from long ago, I'd use a double din permanent touchscreen as it would fit better in this car). The netbook would also be something simpler as well if I didn't already have one with a broken connector for the power supply (I'll pigtail it because I'm cheap).
I intend to release all the schematics for my build once I'm done, as I know that I've had a hard time finding simple designs for these things (Especially the power button dealy--I didn't like the ones I've seen here, and one of the items has gone commercial so no more schematics). Here's what I'll be building:
- 5v USB power supply, switching, 3A (DONE) (Using LM2576)
- 19v (adjustable) switching power supply for the netbook, 2A (DONE) (Using LM2587)
- Automatic power-on power button "pusher" (a relay that is activated for a moment after a short delay once dome light power is on) (DONE) (Using 2 x 555 Timer)
- 4 x 50W amplifier using TDA7851L or TDA7850 (I have both) (To build)
- TDA7419 based audio control (will provide 3-band equalizer adjustments, balance, and fade, along with 3 selectable inputs) (To build)
- Si4734 based AM/FM radio (To build)
- Controlling the above two items with an Arduino via I2C using BSS138 FETs for level conversion
I have all the parts, I just need the time now! Hopefully I'll get it done by PAX East... what do you think? :dance:
Let me know if you have any other ideas!
- Netbook runs on the custom power supply, and automatically powers-on with the relay
- VGA single-DIN Touchscreen works well with the netbook
- 5v USB PSU works and data passthrough is fine
- Arduino is now controlling the TDA7419
- Installed a backup camera in my bumper!
- TDA7851L is not providing any output. I'll have to diagnose why shortly.
- Have soldered together, but not attempted control of Si4734
Alright, TDA7851L works. I didn't have the ST-BY and MUTE lines connected properly. Not loud enough, though, because apparently the TDA7419 has a rather quiet output. I threw in a TL084 to fix that, nice and loud now.
Unfortunately, the TDA7419 seems to be generating some noise internally, a static sound that seems to only come out the tweeter. :( I'm guessing it has to do with the AC Coupling caps that are present in the test design in the datasheet. I'll remove them and see if things improve.
I might just get this done for PAX after all!
Alright! All the noise issues have been solved. The main source of them was using the chip in AC coupling mode--it offers a DC coupling mode which was hard to find. Also, the arduino was injecting noise into the ground on the circuit. Isolating it with a 100 Ohm resistor solved the issue. The volume issues have also been solved--DC coupling mode allows 4 V pp output from the audio IC! :D Sound absolutely excellent, too.
All that is left is:
- Writing the full code for the arduino, it needs to work with the radio IC and an analog potentiometer for volume
- Controlling the radio IC
- Writing a PC interface for all this
If I don't run into any other major roadblocks, this won't take long at all!
- Code for analog potentiometer -> I2C commands working perfectly
- Interfacing via vb.net and serial port -> I2C commands working perfectly
- Controlling radio IC
- Creating a nice looking interface
- Installation into the car. :)
I think I'll leave the radio IC on the backburner for the trip and use my PC Ear for now. I'm short on time. I figure in a month or so I'll have some decent documentation to give you all. This is definitely the right way to do the job!