Prototype assembly

Well 4 hours of squinting in the gloom nudging parts into place and we have our first prototype assembled. Note to self, PCB assembly is best done during the day with lots of natural light, and a magnifying glass or microscope. Of course being impatient I did this at home at 11pm without any extra lighting but the result looks great.

Nano LCD Project

Freshly baked PCB ready for burn in testing

 

A bit of a shame the touch controller I ordered arrived in a TQFP package instead of 44QFN but that’s OK, plenty of other work to go on with before I need to think about the touch interface. For those of you that are wondering, the red PCB is the top of a 2.4GHz Zigbee radio.

Now to port some code to the new board and away we go!

 

Here are a couple of shots at about 30x magnification:

Power supply

From top to bottom, lithium battery management, 3V switchmode, and ~15V current controller backlight boost.

Display driver

MachXO2 CPLD/FPGA, 1Mbit SRAM and the Molex connectors for the iPod Nano Display

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Playing with the Nano Lcd

For the past few weeks ideas have been flying about the office for a new project to bring together the very best of what we do. It started as an opportunity to play with some new toys but we are starting to think that it might roll up nicely into product in its own right, more on that later!

So in playing with some colour LCD screens that have been sliding around my drawer for months I quickly discovered that the large pixels and 12 bit colour doesn’t really meet today expectations for a ‘pretty’ user interface. I really wanted to find a small lcd as the project in mind has to be compact and I after a bit of research found this great project called the microtouch by a guy called rossum. He has managed to make a really  slick touch interface on an 8 bit micro. The ARM version can even serve up wikipedia or eBooks, pretty amazing stuff! There was a lot of mention of a tft screen from China which could be had for about $3 which sounded great. Crystal Fontz even seems to do something similar in 1.77″ which provides a much more reliable supply chain, not to mention datasheets and example source here. This was all starting to look feasible the only problem was finding a capacitive touch glass to match it.

That was about the time I stumbled across this youtube video of the iPod Nano lcd. Its a 1.5″ 240×240 pixel 18bit colour TFT with a capactive touch digitizer which can be had for about $15USD out of China. A seriously impressive little unit but it will take a reasonable level of CPU to drive it. The MIPI interface is a bit of a pain but based on 30mins of youtube footage looked reasonbly possible.

Fast forward three weeks to today and I have a prototype PCB on the desk with probes hanging off while I test out the seven different voltage rails. Being battery operated I was pretty conscious of not wasting power on linear regulators and unfortuately there is a lot of different power requirements on the board. However I think I went a little overboard and the next revision will hopefully be a bit simpler.

Anyway here’s my quick progress shot of the board driving the lcd backlight

SAMSUNG

A quick bit of wire wrap to set the enable lines for the regulators got everything fired up and playing nicely.

SAMSUNG

 

Hand PCB assembly is always challenging when 0402 resistors are involved but this was my first board with 0.4mm pitch BGA packages. Fortunately it was only 6 and 8 ball parts which were pretty forgiving. Some fresh solder paste managed to deposit the tiny dots onto the 0.25mm pads (the flux old paste goes dry and doesn’t flow nicely into the stencil). From there it was a breeze to bump the part into place and reflow in our Sunbeam Mini Bake and Grill!

More to come soon!

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3D printer heated bed

As it turns out you can’t really print ABS plastic onto a cold bed and have parts come out flat. This is something of an inconvienience when trying to calibrate your brand new, just assembled 3d printer. The answer: A very quickly made heated bed!

The bed is a sandwich of MDF, expanding foam, temperature sensors, an etched PCB, and a few misc wires. I laid it all up between two polished floor tiles to try and keep it nice and flat and spaced it with extruded aluminium box section while the foam cured.

Wired it into the Vellman temperature control board that came with the printer (very simple thermistor and relay circuit) and fired it up. The PCB is about 5 ohms and with ~33VDC from a toroidal linear supply I get about 200W of heating. More than enough to get the bed up to the required 80 degrees C, in fact it easily hit 135 degrees in about 45 seconds.

Check out the first print:

60x30x5mm rectangle printed in ABS

I stopped this one part way through so I could show you the scaffolding on the inside, thats a 20% infill. Theres alot of theories on the infill patterns over at the RepRap forums.

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Rapid prototyping

Recently something has been growing in the corner of the Virtual office. A SeeMe CNC rapid prototyping machine, based on the RepRap Huxley.

And in other recent news, The Register reports that The Pirate Bay has added a category for torrenting 3D objects. Data files that are able to be made physical, henceforth known as Physibles. What an interesting coincidence…

 

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Industrial ultrasonics

Here’s a little puzzle for you. Say you have a piece of equipment using an ultrasonic rangefinder. This sensor is mounted near a 12V DC motor putting out several hundred watts. All is well. Then you replace the DC motor with a single-phase AC induction motor. The system then proceeds to go crazy. Why?

The answer is….

 

Pulsating magnetic fields. Arrrg! No amount of grounded conductive shielding can attenuate the AC motor’s pulsating magnetic field from the sensitive ultrasonic transducer mounted nearby. The only reasonable solution is to relocate the sensor more than 30cm from the motor.

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About a scooter

Last week’s excitement was finalising the scooter video. Edited in Cinelerra with a smattering of graphics & effects. Rendering directly into H264 resulted in a broken file so ended up using a YUV4MPEG pipe into ffmpeg. Audio rendered out separately and tweaked with Audacity.

End result – not too bad for a bunch of engineers. Check it out.

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Build Log is up

This is the inaugural post on Virtual’s Build Log. We’ll be keeping you updated with goings-on in the Virtual labs. Stay tuned!

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