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General discussion / What do you do with your spare components?
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Topics
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Topics - nabilt
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General discussion / Found an old pick and place machine. Worth restoring?
Here is a hacker space documenting their attempt: http://http://charliex2.wordpress.com/tag/pick-and-place/
Video of the one I found: http://http://youtu.be/q2gEMrl7_UA
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General discussion / 1GHz Cortex A8 in TQFP
Blog: http://http://olimex.wordpress.com/2012/04/23/blinking-led-with-linux-or-hello-world-with-imx233-olinuxino/
Github: http://https://github.com/OLIMEX/OLINUXINO
For their next revision they plan on using a Cortex A8 processor in a TQFP package, which they found from a Chinese company!
http://http://olimex.wordpress.com/2012/04/24/cortex-a8-in-tqfp-sure-allwinner-a13/
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A10 is Cortex A8 processor running on 1.2Ghz but could be overclock up to 1.5Ghz.
The features are impessive: support for up to 1GB RAM, USB2.0 OTG, USB2.0 HOST x2, HDMI1.3/1.4., LCD, CVBS-OUT, VGA-OUT, SATA,Line-In, Headphone, 10/100M Ethernet, Camera Sensor Interface x2, support for SDIO WIFI, GPS, Gyroscope, Light Sensor, Bluetooth, Compass.
Can boot from NAND FLASH, SD/MMC Card, USB
The company also produces the A13.
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A strip down version of A10 which is same but without SATA interface and HDMI, targeting purely the Tablet market. The new chip is $5 if you by any chance decide to buy one million chips from Allwinner and can be purchased for $10 in smaller quantities.
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General discussion / DIY Super capacitors made out of Graphene
UCLA Video
http://http://www.youtube.com/watch?v=_oEFwyoWKXo
Similar older video from Rice University that used a CO2 laser
http://http://www.youtube.com/watch?v=3O4YV0mrkfQ
Full Paper
http://http://hackadaycom.files.wordpress.com/2012/03/el-kady-som.pdf
Summary paper
http://http://hackadaycom.files.wordpress.com/2012/03/laser-scribing-of-high-performance-and-flexible-graphene-based-electrochemical-capacitors.pdf
Popular method of producing GO - Modified Hummer's method (pay wall)
http://http://pubs.acs.org/doi/abs/10.1021/nn1006368
Paper I found on google about producing GO. Appears similar to Hummer's method.
http://http://www.rsc.org/suppdata/nr/c1/c1nr10549c/c1nr10549c.pdf
I'm not a chemist so take everything with a huge grain of salt.
Producing GO
Googling around it appears GO is cheap to produce, but I can't seem to find any suppliers. It is produced from highly pure graphite (carbon atoms structure in a lattice - stuff commonly known as pencil lead) using Hummer's method (linked above). I haven't paid for the article yet, but the abstract says, "We have found that excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process". The last article linked above says, "9:1 mixture of H2SO4 (95%) / H3PO4 (85%) [360:40 mL] was added to a mixture of graphite powder (3.0 g, 1 wt. equiv.) and KMnO4 (18.0 g; 6 wt. equiv)".
After isolating the solid GO from the liquid it is dried and neutralized to produce a powder. From there it is mixed with water and vacuum filtered or cast into a mold using a centrifuge. The result is what we see in the videos.
Producing Graphene from GO (The cool part)
According to Wikipedia, "graphene is an isolated atomic plane of graphite". It is super conductive, 97% transparent and flexible. There is hope that this relatively new material can be used to create flexible circuits and high frequency transistors. IBM was successful in creating transistors with a 100GHz switching frequency. Researchers at Cornel have shown devices can be created by printing graphene using an inkjet printer http://http://en.wikipedia.org/wiki/Graphene#Graphene_transistors.
There are many methods of producing graphene. One method uses scotch tape to peel layers off graphite. http://www.youtube.com/watch?v=ehvksWx3AJQ&feature=related[url]. Recently the most interesting method is to use lasers to strip oxygen atoms from GO, which is what the researchers did in the video above. Cheap and simple.
[b]Making a supercapacitor[/b]
I'm still reading about their construction, but it appears the researchers use either an electrolyte gel or other type of high performance insulator. In one example they used Celgaurd 3501 [url]http://www.ldcgm.com/Celgard/CELGARD-4550.pdf. Both types don't look like they are easy to find or make.
Conclusion
If you have access to GO sheets then the project looks doable. It seems you might not get high energy and power density unless you use the aqueous electrolyte or ionic liquid, which I'm not sure is readily available. Otherwise, making GO at home does not seems feasible because of the high concentration of acids involved.
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General discussion / How do you manage your parts?
So, I create a utility to do this for me, which has turned into a web app using the Octopart (http://http://octopart.com/) API. The idea is you upload your BOM from Eagle and the app tries to find the cheapest distributor for the parts you don't have. It also keeps an inventory of your existing parts.
It looks like this. Would anyone find this useful?
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General discussion / Programming the STM32F4 DISCOVERY with the Bus Blaster
My initial research lead me to texane's github where he created a linux version of ST-LINK. It doesn't support the STM32F4 yet, but there is a fork which is making good progress. I couldn't get either to work, which is when I turned to OpenOCD and Bus Blaster. A few minor modifications to the STM32F2 scripts and success. First time using the Bus Blaster and couldn't be happier.
Btw, it programs supper fast.
Here are the details
http://http://www.nabiltewolde.com/2011/10/programming-stm32f4discovery-board-with.html