Sorry for the slight delay in updating. I lost a batch of photos after formatting my computer. Anyways, I managed to retake the photos so here goes.
After sitting for sometime in the living room, the CarPC was finally going to be mounted in the car. I had a 3 day weekend so I spent most of that fabricating mounts and ripping the car apart to put the PC in. It was more difficult than I had imagined.
Mounting below the rear speakers turned out to be a pretty good idea because the speakers provide quite a rigid support for the motherboard and the power supply. Once everything was screwed down, going through bumps and potholes wasn’t a problem. Nothing was shaken loose over the course of a week that I had the CarPC in the car.
I had to redesign the inverter control because the first one was giving me a lot of problems with timing issues and unwanted feedback from the motorized antenna. I also isolated the PC system and the inverter controller by using an optocoupler to reduce the unwanted feedback that prevented the inverter from properly switching off. I will upload the full schematic once I draw it out.
I also had a bit of problem with the inverter shutting down very quickly when the car engine was not running. I suspected that the inverter was not getting enough voltage from the battery. So I checked the wiring from the battery to the inverter and I realized that at full load, the drop across the fuse was 0.5volts. Obviously the contacts were not good so I took it apart and rewired it and the inverter worked like a charm. Now the CarPC remains on even when I turn off my car engine.
Initially I wanted to mount the monitor at eye level using the windshield mount so I don’t need to take my eyes off the road to use the screen. But the problem was, the monitor was so big that it blocked off a large area of my vision. Also the cabling would make the whole setup very messy. So I decided to mount it lower.
By the way, I bought the Lilliput 7″ touch screen and I’m glad I did. Resolution is very good and the display is just brilliant. I highly recommend anyone installing a CarPC to get one of these if you are on a budget. The USB touch screen works flawlessly too.
In order to mount the screen there, I had to make some modifications to the original compartment. I drilled and secured the LCD mount using some nuts and bolts and I also drilled a hole at the back so I can feed the monitor signal and power cable in.
There’s still ongoing testing of the system. The full software configuration and testing will be explained further in the next post. For now, this is how it looks like at night:
Running Centrafuse. The blue light comes from the power switch. Bright blue means the CarPC and the inverter is running. A dimmer blue means only the inverter is running and the CarPC is off. No blue light means the inverter is off.
I managed to solve the ground loop noise problem by grounding the motherboard properly to the car. Now I have a monitor interference problem which I suspect is due to the rerouting of the monitor cable this afternoon because before this there wasn’t any. I have also ordered an op-amp so I can build a small amplifier to slightly amplify the incoming signal from the CarPC because now the volume of the CarPC doesn’t match the volume of the radio or CD player. It is too soft even at full volume. With the op-amp circuit, hopefully I can further reduce the noise interference by increasing the signal-to-noise ratio.
Update 24 September 2009: Pictures
The display flickering was caused by the 12v supply itself and not interference picked up by the video signal cable. Noise was probably introduced into the 12v line by the alternator. A temporary solution is to use a switching power supply that converts the output of the 240v inverter back to 12v. Because the switching power supply runs at a higher frequency, the flicker was not visible. A more permanent solution is to use a 12v to 12v switching converter that isolates the 12v input from the car. Again, the switching will be done at a higher frequency to reduce the flicker.
I have also finished building the pre-amp and it should be in by this weekend.
Next: CarPC Project: Software Continue reading