Mark's Stuff

True to form with my most recent car, a VZ Holden Adventra LX6, its taken only a matter of months before pulling apart the interior panels to add some more electronics.

This effort is nowhere near as obstrusive as the Jeep’s home grown touch screen PC/media player/GPS, and I’ve tried to keep a factory look and feel as much as possible.

The bits that I’ve added are:

• Nokia CK-7W bluetooth car kit
• GME Electrophone TX-3400 UHF Radio
• RFI AP-454 glass mount antenna
• UDC Holden iPod interface

I actually installed the bluetooth kit a few months ago. A pretty straight forward install. I just bought the factory button from a local Holden dealer and attached a new plug into the wiring loom that’s sitting under a panel at the passenger’s right leg.

The 2.5mm socket above the phone button is for the phone charger. Good for those long weekends away! Its a bit unfortunate that the phone is upside down, but I wasn’t bothered trying to find if they also make one the other way up.

Last week I received my iPod interface from Vlad (http://udc.aus.googlepages.com/holden) and took to the factory head unit with a screwdriver and soldering iron to add seamless iPod support.

The only thing I did differently to Vlad’s recommended install was the way I routed the cable. Instead of cutting the cable and running it through to the arm rest compartment, I removed the centre console, drilled a 13mm hole, and threaded the mini din plug that comes with the kit through to the back of the head unit.

The insert to the compartment has only got three sides, which you can sort of see in the picture, It also has a false bottom, so its easy to drill out a hole big enough for the mini din plug through the console base, and then just check out a 5mm hole for the wire in the bottom of the insert. The compartment insert is screwed in from the bottom though, so I had to remove the centre console to get to it.

My Nano fits perfectly, but I’m not sure if the bigger iPods will fit nicely here.

And a close-up:

Last but not least was the CB install. This one was a little fiddly because of the tight space I tried to fit it in. Ideally it would have gone into the compartment above where it is now, but the radio was about 10mm too wide. I was going to take a few more photos of the iPod cable run, but that would mean removing the CB to get the console back out.

The GME Tx-3400 is a remote-head radio, so the main part of the CB is tucked up underneath the glove compartment. That caused the sound to be a bit muffled, so I used the external speaker that came with the Nokia car kit (The car kit audio routes through the radio speakers) and mounted it just behind the centre console. Much better sound!

After much talk, and further proscratination disguised as “finalising the design”, I finally convinced myself to take a couple of weeks off work to build a deck out the back of our house.

Armed with a truckload of treated pine and merbau, a few hundred galvanised framing nails, a box of 2000 stainless steel screws, a power drill, two cordless drills, a circular saw, a jigsaw, a drop saw, two saw horses, framing gun, chalk line, laser level, sprit levels, line level, tape measure, two shovels, a pick, one hired post hole digger (broken), one hired post hole digger (working) and a 4m² skip, my dad I got to work.

Day One was marking out all 19 post holes, digging them cleaning them out and setting up string line stakes for when the posts got put in.

Day Two had us waiting around for the concrete to be delivered. It was scheduled for midday, and by 10:30 we had double checked as much as we could, so got to demolishing the front brick fence while we waited. The concrete turned up around 12:30, and we had 20 minutes to barrow almost one cubic metre from the truck around the back and fill up the holes. String lines went up, the posts stuck down into their holes, and we called it a day while waiting for the concrete to set.

Day Three was Framing Day. Five bearers, and eighteen joists later and we had a (pretty much) perfectly level footing to work with.

Day Four was a lazy start waiting for the merbau to arrive. It turned up just after lunch, and we only managed to lay 5 rows of decking before the umpire called stumps due to bad light.

Days Five to Eight had as doing the same over and over. Choose a “random” length of merbau so that the joins were well spaced out, bevel the end, find a suitable matching piece, bevel the end. Lay them down, measure against a chalk line, adjust spacing, drill and screw. Repeat for 63 rows of decking, to lay a total of 390 linear meters. With a rest day in between.

The last day of deck laying also included making a frame for the BBQ to sit on, and finishing up the base boards making up the edge of the deck. A plumber was enlisted to hook up the barbie to natural, then a couple of coats of Cabot’s Aquadeck for protection, a quick trip to Ray’s Outdoors for some furnishing, and we’re ready for entertaining!

The only outanding thing now is to find a suitable sink to install next to the BBQ. Hot and cold water and waste are ready to be hooked up, there’s nothing to hook them up to yet

Oh, and I suppose it would be nice to get some nice real grass out there instead of the rollout plastic stuff covering up the dirt at the moment!!

After many failed attempts at findind a suitable, cost effective, amplifier solution to drive all the ceiling speakers throughout our house I decided to finally give up and make my own.

So I got a hold of two 25W amp kits based on an LM1875 IC, and a power supply suitable to drive both of them.

Below are pictures of firstly the power supply driven by a 160VA 18-0-18V toroidal transformer, and secondly of the two amps mounted together and attached to the heatsink on the rear of the case. Each transformer can comfortably drive 4 x 25W amps.

The case is just a cheap 19″ rack mount enclosure from Jaycar which is quite easily customisable with adjustable mounting rails, and is pretty solid once assembled. As you can see below, plenty of space for another 3 power supply circuits and 6 amps, to make the unit up to its capacity of 8 channels. I could potentially squeeze in another 2 channels, but then heat starts to become more of a problem, as does finding rear panel space for connectors.

Yes, I know the heatsinks aren’t straight.

Add four dual 50kΩ log pots for stereo volume controls, a power switch and LED on the front, and the amp is ready to go. Well, except for the fact that there’s only 2 out of 6 channels built so far.

The biggest challenge of this project was eliminating the hum that I first heard when I turned it on. I knew the electronics were fine, as the amp was very quiet when I first tested it outside the casing. The hum was very much indicative of interference, likely caused by a ground loop.

The first step was to change the wire from the input terminal, to the pot and then to the amp. I made the mistake of using cat6, as it conveniently has the right number of wires. But no good for unbalanced audio. The noise reduced significantly after replacing it with shielded coax. But it was still there.

I soldered in extra ground wires, I tied the ground to the mains earth, I moved wires away from the transformers, all to no avail. Then eventually when probing around with the multimeter, I accidentally shorted out the negative input signal wire to the casing of the volume pot, and the instantly disappeared. Now I have zero hum all through the volume range. And the 25W/ch is plenty for the ceiling speakers. Not sure about driving outdoor speakers for the deck (when it gets built), so I may need to make a 2×50W amp for those.

Next step is to introduce a microcontroller to drive volume and turn channels off by relay (power saving) via RS232.