Monthly Archives: March 2007

IC Friday: Analog Devices’ AD639

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The AD639 is a general trigonometric function generator where the output is a scaled ratio of two sines, where each sine has tunable parameters. The package on this one was another ceramic case with a gold cover that was held on by solder. Heating the case and pushing over the solder revealed a very clean chip with a seemingly small number of transistors. No markings were found on the chip other than the model number and Analog’s logo.

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( ad639.pdf )

Pictures of the European (PAL) PLAYSTATION3 mainboard

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Only days after the European PLAYSTATION3 launch and people are already taking their systems apart. Unfortunately, I didn’t find any easter eggs on the PCB. The biggest problem should be in the absence of a hardware PlayStation2 emulator resulting in some controversy. I am not sure if it is apparent from these pictures that the chip is missing, so I will try to post pictures of the U.S. or Japanese mainboards if I can find them.

( Via Engadget )

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[WordPress didn't thumbnail these correctly, sorry!]

Setup wizard for Linksys WGA54G wireless game adapter

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A couple times a year, I have to reconfigure my Linksys wireless game adapter. Every time I figure that the setup utility is online and realize that it is nowhere to be found. Consequently, I spend about an hour every time trying to find my original install CD and cursing Linksys. I am guessing that some other people might be going through the same process a couple times a year, so for you, here is the setup utility.

( wga54g-setup.zip )

IC Friday: Cypress Semiconductor CY7C172-35PC

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Here we have a 4K SRAM from Cypress. Looks like the original design is from 1985, however, the date of manufacture is unknown. This chip was in a skinny DIP package but it was ceramic instead of plastic. I carefully opened the package using a chisel and hammer and was surprised that the die had a bubble of soft, clear material over it. It might be due to different mechanical properties of the ceramic case and the silicon. Regardless of the reason, it made it much easier to recover the intact die.

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(CY7C172-35PC datasheet still missing in action.)

National Semi. app. note on capacitor soakage

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Bob Pease is regarded as Mr. Analog by many people and he continues to explain misunderstood phenomena in a wide range of applications.  The first edition of this note on capacitor soakage was published in 1982 in EDN, the year that I was born, and is still one of the few decent articles I can find covering the subject. This should prove useful to designers of sample-and-hold and integrator circuits along with those who are interested in a deeper knowledge of capacitors.

Rotary evaporator update

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Since the last post about the rotovaporator on a budget, we have made some improvements.  First, we added a transmission to lower the power delivered to the motor and avoid the need for any kind of cooling. Second, we added a higher stand to allow us to sonicate the flask while rotating it.

P.S. We also have a DIY centrofuge.

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How to make a rotary evaporator on a budget

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In case you need to create a monolayer of lipids inside a spherical flask and don’t to spend $3000 on a commercial rotary evaporator, this is the design you need. Justin Ingram and I set out to build such a device from things found around the lab for a small fraction of the cost.

The first step was to create a commutator that could support the flask and allow for the evacuation of the solvent vapors from the flask. We used a piece of Teflon coated stainless steel that was held in a piece of Delrin with a pair of Delrin spacers. We also used a planar ball bearing to lessen the friction between the stainless steel and the bushings. A piece of a 5ml syringe was attached to the other end of the tube and was then was covered in parafin. This piece was just the right size so as to fit into the opening of the spherical flask and be able to support its weight.

The next step was to provide the rotary action. We found a DC motor around the lab which was connected to a standard variable power supply. We transferred the force from the motor to the flask by a belt system implemented using a standard rubber band. Although the motor drew almost 1.5A while in operation, it did not get too hot over a period of half an hour. We are working on a thermocouple to allow us to attach a peltier device with a  heat sink or just a heat sink to allow for more efficient cooling.

The main purpose of the vacuum system was to collect the solvent vapors, not to reduce the pressure inside the flask. For this reason, we were able to loosely connect a pair of luer-lok adapters together to allow for them to rotate and did not worry about the poor seal. We turned on the vacume system and verified that the vacuum was good enough to take in smoke from the surrounding area and assumed that it was sufficient. The vapors that we are working with are that harmful, but it is also possible to run this system inside of a fume hood. The commercial system also has a water-cooled condenser for collecting the solvent, but it is snowing outside, so we can put something out there to act as a low-cost condenser.

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( evap-action.AVI )

Analog Devices: longer life for CMOS devices and avoiding passive component pitfalls

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Something to do on the day after St. Patrick’s day? Look at application notes. By way of looking for some video encoders to generate all of the timing signals I came across an app note for increasing the longevity of CMOS devices and another regarding appropriate selection and use of passive components. They are both a little dated but still have applicable information to ever-shrinking devices.

( an-348.pdf ) ( an-349.pdf )

How to make your USB WIFI adapter into a “PROFESSIONAL” grade tool

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The short answer is to put a SMA connector on it. From an RF standpoint, many of the USB WIFI adapters have pretty decent chipsets that are used to make up for their small antennas and limited board availability. In the case of the DLink DWL-122 (yes, I mis-spelled it on the board), the choice is a small f-strip antenna. The feed port can be identified by the tapered, triangle-looking trace, so that is where the SMA center feed will go. The other pad is for the return and will be connected to the outside of the SMA connector. Now that the USB device has a standard RF port on it, it’s quite easy to experiment with some personal antenna designs. The performance is not optimal since the tapered feed pad along with the SMA connector will create an impedance discontinuity, but it is quite easy to get better performance with simple designs. Below are comparisons of the signal strength with the f-strip and the whip antenna from the Fonera.

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