Iris Transmitter

Posted on 2012-09-11 by Nigel VH

This is a project I’ve been working on for a while, and have refrained from posting about it for lack of specifics. Well now I have specifics. The boards are in and I’ve assembled my first home made transmitter!

I’ve always thought it would be cool to make my own transmitter, but due to either a lack of time, or a thought that I didn’t know enough about RF, I hadn’t gotten around to it. I ended up stumbling across a very similar design by one of the guys on an IRC channel I frequent, and began an email correspondence with him. After some talking, I decided to try my hand at it.

The goal was to create a low power transmitter, that is compact enough to use on a rocket or high altitude balloon flight, that is frequency agile within an amateur radio band and that, with component choices during buildup, is capable of operation on any of the 2m/1.25m/70cm/33cm amateur radio bands.

As I just got the boards and assembled one last night, I don’t have the software to actually run the transmitter done, however, I’ve loaded a few test programs to it, and have confirmed that the processor is running, the VCXO is running, the regulator for the RF transmitter is running and the PA temperature sensor is working.

In summary, what I haven’t tested so far is the PLL, the PA, and the RF power detection circuit. (Most of what actually makes it a transmitter…)

So, while you’ll have to wait on specifics for power output (I’m hoping for about 1/4W) and whatnot else RF characteristics, I do have photos of the boards.

The above is how the boards came to me. For this order, I used a new fab place that does boards cheaper than many others. Go ahead and look them up at oshpark.com. For the size of these boards, it was about $40 for the six.

Here’s a closeup of just one by itself. I’m pretty pleased with this fab place. Purple boards and gold pads. Classy.

Here’s another shot with a ruler. The boards are 2.75″ x 1.5″.

Here’s a closeup with everything on the board populated. Minus the five pin headers on the top and left. Though, those aren’t strictly necessary. Wires could be soldered there instead of headers.

Here’s a shot of the bottom side of the board for good measure. The fab place will do bottom silkscreen for no extra charge, but since I wasn’t placing any components on the bottom, I didn’t bother with any silkscreen on the bottom.

Enjoy the photos, and hopefully I’ll have more progress with it soon!

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Legalese Part 4

Posted on 2012-09-05 by Nigel VH

Last Thursday I ended up getting an email from a complaints investigator at the DOL. He let me know that he believed that not having the zip code did not make my Report of Sale invalid, and that he had let the towing company know this information the day before.

At that time he also gave them 10 days to respond in writing. He also asked me to provide scans of the documents they’ve mailed to me.

Obviously, this is good progress, and I’m rather pleased to have someone looking into the matter in an official capacity. I scanned the documents and sent them along right away.

Now it’s been six days, and I haven’t heard anything more about it, so at this point we’ll wait out the remaining four days and see where we stand. Hopefully progress continues.

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Meyer Lemon Tree

Posted on 2012-09-04 by Nigel VH

In July, 2012, I visited with a friend of mine who was living in San Jose, California. He ended up showing me a small Kumquat tree he had picked up, and planned to grow in a large pot.

I became rather attached to the idea of a potted fruit/citrus tree of some sort. Unfortunately, even the dwarf varieties of many fruit/citrus trees still grow to be rather quite large, so that somewhat limits the options. However, one stuck out as a good contender for size, the pacific northwest climate, disease/pest resistance and aesthetics. The Meyer Lemon.

From my reading, the Meyer Lemon is now known as the “improved” variety due to increased disease resistance. This in addition to a workable size of 4-5′ tall when mature (if pruned) and a tolerance for the climate in the pacific northwest made this an easy choice. Plus who doesn’t like some lemon with some tea or a coke?

The flip side to this story is that I have a terrible history taking care of plants. About the only plant I can reliably keep alive is “lucky bamboo” and that’s because I can fill up the reservoir with water, and it will be good for the next week or two. This lead me to pick up a soil moisture meter at my local home improvement store. The most basic one they had also had a light sensor and a pH meter, which both were somewhat interesting. In any case, the meter became a useful tool in determining what the tree needed, but not in making me into an attentive caretaker.

As such, I needed a device that could live in the pot (water/bug/whatnot proof), and somehow get the necessary information back to me, without me having to go and check on it (the issue in the first place). I did a little searching and found the Botanicals Kit on SparkFun, but that’s obviously not waterproof, and requires power and ethernet cords to the pot. Quite a hassle when it’s outside… Looking over the available schematics, I decided I’d build my own. It would need to run for a reasonable period of time on batteries, and would report the data back to my computer wirelessly.

Working with an ATmega328 as the brains of the system, a couple ZigBee Series 2 wireless radios, and some NiMH rechargable AA batteries, I had the basis of the system to be. The sensors (soil moisture and light intensity) were easy to implement. A couple of stainless steel rods connected with a junk-box transistor and some resistors formed the soil moisture meter, and a junkbox solar cell formed the light intensity meter. The harder part was going to be getting the system to run for a reasonable period of time on a few AA batteries.

I ended up spending a few afternoons fiddling with the sleep and power saving modes available with the ATmega328, and managed to get sleep power draw below 1mA. (This number depends A LOT on voltage. At 5v it draws approximately 0.8mA, however, at 4v the consumption is an order of magnitude less at 0.07mA. Also note I’m not using any of the deep sleep modes. I had to keep the main clock running to be able to wake from a timer. Deeper sleep modes offer a lot more power savings.)

However, the power draw while active is much larger, bringing the ATmega up to full operations, taking measurements and powering up the Xbee radio and transmitting data. At 5v this adds up to about 140mA. Though I suspect it’s a lot lower at closer to 4v.

Unfortunately, this makes it rather hard to guesstimate how long the batteries will last, but if the system continues to draw power at a 5v rate (ignoring that the voltage will get lower as the batteries run down), it should last about two weeks on a charge. However, as the batteries get lower, the system will end up using far less power, so how long it will actually last is anyone’s guess. That is until the batteries run low and I go and charge them. Then we’ll know exactly how long they last.

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Legalese Part 3

Posted on 2012-08-30 by Nigel VH

Alright, so it’s been a bit since I last posted on this topic. Here’s the update so far.

On Friday the 10th, I filed a complaint with the DOL concerning the matter, and then the next morning the 11th, I sent the towing company a certified letter explaining that they cannot hold me liable for this vehicle and included photocopies of the various documents saying that I filed my Report of Sale and it is valid.

So, I waited. Hopefully I’d either hear from the DOL and we’d move on from there based on what they said, or I’d hear from the towing company and hopefully they’d back off. Neither of which happened. So I waited a bit more.

Anyway, come Friday the 24th (two weeks after submitting the complaint), I call up the DOL to ask about the status of my complaint. Apparently they didn’t have my complaint on file. So I give the gal my email address, the email’s subject, the date at which I sent it, and she managed to find it. Apparently they’re transitioning from one group handling this, to another group, and some things are being missed.

Anyway, later that day I received an automated email from their systems saying it had been received, so hopefully at this point it’s being tracked a bit better. Anyway, It’s now been about a week since then, so I’ll wait till early to mid next week and reach out to them again to see where we’re at. It’s dealing with the DOL, so that’s not the most fun, but at this point, I’m not sure what else I can do short of the even less fun option of getting a lawyer involved. So, we’ll see where it goes.

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Stepper Clock – Part 2

Posted on 2012-08-23 by Nigel VH

Last night I hooked up the stepper clock and loaded in some test software. This software just runs through and stops at each number, then restarts and does it again. Here’s a quick video!

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