Posts Tagged Mods

My new Chinese laser cutter!

For my birthday, my entire family chipped-in and gave me most of the money to buy a (relatively) cheap laser cutter directly from China. I had seen several Hack-a-day articles about these machines, and I’ve got experience with 3D printers, so I thought it was something that I could handle. Boy, did I have a lot to learn.

The path the slow boat from china took

The path the slow boat from china took

To begin with, I looked around on eBay and Alibaba. I noticed that 90% of the ~$1000 units are almost identical. There are occasional small differences such as pointing laser, whether it has a spring loaded “work clamp,” whether it has a raising-lowering bed, etc. I found one that claimed to have a larger bed than any other that I’d seen (mistake #1). I don’t know why I accepted that a machine that looked like every other machine out there would have magically increased the work size, but I did, and it doesn’t.

Because I was mentally set on this machine, I was willing to accept the shenanigans of the seller (mistake #2). The trouble began when their “free shipping to the USA” became $200. I thought “That’s kinda annoying, but not the end of the world.” The shipping charge was on par with other vendors. The next problem became that the $200 shipping was by boat, and F.O.B. (Mistake #3). Alibaba doesn’t support shipping by boat, and at this point the vendor and I agreed to leave the relative safety of Alibaba (Mistake #4). I requested a refund of my Escrow and it was granted.

A quick note about how Alibaba works, for the uninitiated. Alibaba is a marketplace, like eBay. Unlike eBay, however, Alibaba provides some additional protections to the buyer, and less so, the seller. When you purchase something from a vendor and make a payment you pay Alibaba directly, and that money is put into an Escrow account for the transaction. At this point, the Seller is assured that the money is there and they are guaranteed payment if they hold up their end of the deal. The seller, then, ships the product with an Alibaba approved carrier (like DHL, EMS, etc.). When the buyer receives the product and decides that it was accurately represented and meets expectation the seller is paid and the escrow is closed.

If you decide to leave Alibaba, it’s the wild, wild … east? The vendor really wanted to be paid by a wire transfer, which is the system that you see in spy movies. Bank account number, routing number, etc. The thing about a wire transfer is that there are NO protections. That money is gone, forever. If the vendor is feeling generous they may give it back if there’s a problem, but there are no systems in place for you to dispute it. There was no way I was going to go for that. I got them to agree to accept PayPal, which for all their faults does provide some buyer protections. Paypal makes their money by levying a surcharge on business transactions; the only way I got the vendor to agree to this was by paying the surcharge myself. In my mind, it was a worthwhile investment in insurance.

Ok, at this point I’ve paid the vendor and they’ve sent me vague information about when the ship will be leaving the Qingdao port. Then, one day I get an email from them about filing an ISF (10+2) form. I had no idea what this was, and I literally called the Port of Portland to ask them. They basically laughed at me. Apparently, the ISF is a form for a system that was introduced after the Sept. 11 collective mindless panic. Someone had the thought along the lines of “zomg, someone could put a bomb in a shipping container and blow up an entire city!” So, of course the government intervened and invented yet another complicated, expensive, process that can only really be done by a customs broker.

Now I need to find a customs broker. Off to Google… Whelp, no one has a ratings site for customs brokers. All my usual methods for deciding on a service provider fail. I find myself at the port of portland website and staring at a list of what seems like a hundred brokers. I literally choose one at random (mistake #5). I call their number and someone assures me that I’ve got plenty of time to file (Did I mention that you have to file the form three days before the ship leaves the last foreign port, and that failure to comply can be a $5000 fine?). I never hear from him again. Two days later I get a call at 3:00am from China. They’re calling to yell at me about the fact that my form hasn’t been filed and that I needed to do it right now. I calmly (lucky for them, my 1-year old wasn’t woken) explain to them that no one is awake or willing to take my calls at 3:00am. I’m not happy. The next morning I googled for “Customs broker portland oregon.” I choose the first link. My thinking is that google’s magic algorithms must know something more than random guessing. The new company is fast, responsive, and mostly a pleasure to work with.

Importing something substantial (I’m not sure what makes something substantial, but stay with me) is an expensive affair. The ISF form costs $35 to file. Great. Wait, I also have to become a customer of the brokerage company, $50. I need to have an ISF bond, $100. Don’t forget the customs bond premium, $45. Someone needs to enter the customs yard, $125. I haven’t even mentioned duty yet (this is what most people think of when importing), $26.50. By the way, any device that “emits radiation” has to be FDA accepted (they mean all radiation. Yes, I know that LEDs emit radiation, so do radios, you get my point), that’s another $35. So far were looking at about $400 in addition to my $200 shipping. Awesome.

You can see in the image above that the boat is going to Long Beach, California. Cool. I don’t live in California. The whole time I’ve been talking to them I’ve said Port of Portland perhaps a dozen times. I’m panicking a little. About two days before the boat is set to arrive in Long Beach, I get a call from a company at the Port of Long Beach. They were wondering when I would pay their fees. What? I wasn’t aware I had contracted with anyone at the Port of Long Beach. They had asked me about who my customs broker was. It seemed like this was the kind of thing that they could bill my customs broker for, and I had them do that. These guys charged another $160 of fees, including my favorite, the “Clean truck fee.”

Now, at this time (October 2014, and persisting now, into January 2015) there is a major bottleneck at the Port of Long Beach. My delivery was delayed a bit over a week because of this.

I was curious how I could get a shipment delivered to Long Beach, and have it go through customs in Portland. Apparently, it’s possible to move merchandise across the country that has not gone through customs. It just has to go to customs before it goes to the customer. That seems strange to me.

Anyway, the truck eventually got my package to Portland, and I drove up one day to get it (I had 2 days before I’d start getting charged warehouse fees). They put it on a forklift and surprisingly gracefully placed it in the back of my 4-runner.

All told, the cost for the machine was $700 + $200 shipping + $667 in customs fees. I feel a bit nauseous typing that out. Even more so when I add them and have to say that it was $1567 in total. Though, when I remember how much a decent laptop costs, I feel a little better. ūüôā

The rest of my laser-cutter adventures were documented in video. Please enjoy the YouTube playlist below:

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Emma’s Red Dresser

Katie and I needed to get a dresser/changing table for Emma.  We decided to find an antique dresser to redo rather than the pressed-wood pieces of crap you can buy today.  We found one at the Corvallis ARC that fit the bill nicely.  Unfortunately, I neglected to take photos of it before attacking it with the sander.  The following two photos are during the sanding process, though.

Starting to sand off the stain

Starting to sand off the stain

Some of the drawers before sanding

Some of the drawers before sanding

The stain and finish that they used was nasty to sand off.  When it got hot from the friction, it would melt, kinda, and gum up the sand paper.  Eventually, and after many sheets, we got it all off.  In the process, I bought a Ryobi Corner Cat which I like O.K.  I had to replace the velcro pad that holds the sand paper because it wore out.  Shipping took a bit, but the replacements were only a dollar or two.

Once I got all the stain off, I could assess the level of wear the dresser had accumulated over the years. ¬†In total, it wasn’t bad. ¬†It was pretty interesting to see how construction methods have changes over the years.

Slightly distressed corner

Slightly distressed corner

In getting ready to paint, I masked off the inside of the chest openings.  In this view, you can see the construction.  Lots of random sizes of lumber, everything is mortised, etc.

ready to paint the chest

ready to paint the chest

It took a ton of coats to adequately paint the dresser. ¬†It didn’t help that we did this at the height of summer, and it was HOT. ¬†The paint was practically drying as soon as it left the pail. ¬†This left a very poor finish, and honestly, I’m a bit disappointed in it.

The chest is painted

The chest is painted

Eventually, it got to a point that I could live with, and we reassembled everything. ¬†I chucked the knobs into the drill to sand the finish off. ¬†I’d like to eventually get some antique porcelain knobs. ¬†I think that would look really nice.

One extra thing we had to do, that I don’t have pictures of, is replace the drawer bottoms. ¬†Most of them were in really bad shape, and weren’t even square! ¬†I just bought some plywood at the store and had my friend Tom cut them to size on his table saw.

Painting and reassembling all finished

Painting and reassembling all finished

We’re all finished! ¬†Here’s the dresser in its new home, complete with changing pad. ¬†Hopefully, as Emma grows up, she’ll like and appreciate it!

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SKY65116 Amplifier

Amplifier breakout board

I’ve finally gotten around to assembling a breakout board for the¬†Skyworks¬†SKY65116¬†UHF amplifier. ¬†It’s really amazing how the state of the art in RF ICs has advanced. ¬†They can still be on the expensive side ($6 at digikey), but still relatively cheap when you consider the cost of all the support parts that it takes to build an amplifier from a RF transistor. ¬†This particular amplifier has a 50 ohm input and output, and 35dB of gain. ¬†It works from 390Mhz to 500Mhz, which means its perfect for the 70cm ham band. ¬†The breakout board is stupid simple, copied directly from the evaluation board schematic in the datasheet, ¬†but I’ll include schematic and design files anyway.

Source for the amplifier test

This is the video transmitter from my first person¬†video experiments. ¬†The performance was pretty terrible, even after I tested it using different receive antennas. ¬†I’ve even purchased a receive-side amplifier to try, but haven’t done anything with it yet. ¬†Anyway, the transmitter had a built-in antenna, so I wasn’t sure how I was going to add an amplifier. ¬†I ended up assuming that the output would be roughly compatible with an 50 ohm load. ¬†I unsoldered the antenna and installed a bit of thin coax to the antenna port. ¬†I scratched off some of the solder mask on either side of the board near the antenna port to make sure I had a solid electrical and mechanical ground connection. ¬†The transmitter is pretty crappy, and the prices you can find online are COMPLETELY RIDICULOUS! ¬†I wouldn’t pay more than $20 for it. ¬†I think that’s about what I paid, it was on clearance.

Amplifier test configuration

Testing configuration

This image is the testing configuration I used. ¬†The camera, power board and transmitter are in the top of the image, and are exactly as I used them for first person video. ¬†The added coax can be seen going into the amplifier on the left. ¬†Coming out of the amplifier is the cable going to the oscilloscope or spectrum analyzer. ¬†The amplifier wasn’t inline all the time, though. ¬†I measured the output power from the transmitter at about 25mV into 50 ohms using the oscilloscope. ¬†Using Minicircuits’ handy table that comes out to be about .01 mW, or -19 dBm. A measurement from a spectrum analyzer verifies the -19 dBm measurement from the o’scope (see below for image).

NTSC modulated spectrum (click for source)

I’ve attached a very nice graphic from wikipedia that describes the components of modulated NTSC video. ¬†There is something happening here that isn’t obvious, so I’ll explain it. ¬†In the spectrum analyzer image, below, you’ll notice that I’ve labeled the luminance and chrominance carriers. ¬†The luminance carrier is really the main carrier for the entire signal. ¬†It comes from black and white TV era. ¬†There are significant DC components in NTSC video, so this carrier is very important. ¬†Notice, in the graphic above, that the luma carrier is 1.25 Mhz above the lower edge of the band. ¬†This is because NTSC video uses what’s called VSB, or vestigial side band, which means that the lower half of the signal is attenuated. ¬†This reduces the spectrum necessary to transmit video. ¬†The choice was made to include the carrier and 1 Mhz with of lower sideband while removing the rest. ¬†Later, when color TV was added, they needed a way to encode color. ¬†This is done by adding another carrier and encoding hue and saturation by modulating the phase and amplitude of this carrier. ¬†All this is explained at length, and probably much better, in the wikipedia article on NTSC.

Source spectrum

In the spectrum image I’ve included above, it’s clear that the little transmitter uses AM rather than VSB. ¬†You can tell because AM modulated signals are always symmetrical with respect to the carrier. ¬†If it was VSB, the spectrum on the left side of the carrier would be suppressed. ¬†You may notice that the left and right side don’t look 100% alike. ¬†This is because it takes time for the analyzer to sweep the band (it does this 30 times a second), and it will be analyzing the spectrum of a different part of the image as it scans.

Source signal through unpowered amplifier

Well, that was an unexpected tangent! ¬†Back to the amplifier… ¬†In the above image I have the amplifier in the signal path from the source to the analyzer. ¬†It’s disconnected from any power. ¬†I’m a little off on the “-60 dBm” text, it’s closer to -64 dBm. ¬†I was interested in seeing how much RF would leak through an unpowered amp. ¬†It appears that the amp provides a little more than 40 dB of forward isolation between the input and output when it’s unpowered.

Amplifier powered on

Finally, this is the spectrum when the amplifier is powered on. ¬†I had to install 40 dB of attenuation on the analyzer to capture this image. ¬†The peak of the carrier is almost 5 dB lower than the top line, so it’s about 36 dB stronger than the input. ¬†This is inline with expectation, as the amp specifies +35 dB gain. ¬†The resulting signal is +15 dBm, which is a modest 32 mW of power. ¬†The hope is that through a better antenna and some amplification I can get better performance from the video link.

A word about the legal implications. ¬†Ham radio people are notoriously concerned with the rules of everything they do, so I feel obligated to mention them. ¬†In the U.S., at least, 434 Mhz is a commonly used ATV (amateur T.V., or “fast scan TV”) frequency. ¬†There is some concern due to the proximity to the ¬†“satellite only” frequency band of 435 Mhz to 438 Mhz. ¬†This means that the carrier is sometimes shifted to 433.92 Mhz, as this transmitter is. ¬†Some of the sidebands still end up in the satellite only band, but with much lower power. ¬†Because this amplifier only outputs +15 dBm I’m very unlikely to upset anyone with its use, though I should think about adding an overlay with my call sign to the video at this power level. ¬†Maybe I’ll have a new 8-bit microcontroller project…

eagle files

gerber files

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The Camera module’s new look

Painted to match

Taking advantage of the crummy weather, I decided to paint the camera module to match my plane. ¬†I didn’t just do it for the aesthetics, no really, I swear. ūüôā ¬†Actually, the real reason I painted it was to prevent stray light from making annoying reflections on the inside of the window.

Read the rest of this entry »

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Kadet video downlink

Camera installed with Transmitter

I’ve just finished building a camera module for my Kadet. ¬†When I was building the plane I knew that I was going to try and put a camera and transmitter approximately where the pilot’s head would be in a real plane. ¬† Read the rest of this entry »

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