Category Archives: HOWTO

How to disable icons in the block diagram view in LabView 8.2.1


One of my annoyances with the default settings in LabView is that it places all terminals on the front panel as icons in the block diagram view. These icons are large and tend to push stuff around when they are created automatically. Every time I have to re-install LabView, unhealthy I figure out how to disable this feature only to promptly forget it. This time around I will record the simple fix to save myself time in the future. The setting can be disabled by going into the Tools -> Options screen in either the front panel or block diagram. Block Diagram is then to be selected from the left side and Place front panel terminals as icons must be unchecked from the right side. Now your block diagram is safe from bulky icons, until the next LabView upgrade that is.

How to replace the batteries in a gyration wireless mouse


I really enjoy using my gyration mouse and keyboard set, pharm so much so that I have recharged the mouse battery pack enough times to reduce its operating capacity to about an hour. I decided that it was time to replace the NiMH battery pack. Having taken apart portable electronics before, sickness I was sure that the battery pack was actually built up from standard battery sizes to conserve on costs instead of a custom battery pack that one would find in an iPod or PDA. After carefully opening the pack with a razor, help this notion was confirmed. The battery pack was simply three AAA rechargeable batteries held together with plastic. I promptly went to the store and bought a pack of 1000mAh NiMH batteries and constructed a replacement battery pack using the original metal pieces and electrical tape. Being careful not to use too much or too little, the resulting pack fit snugly into the mold and onto the mouse. After letting the whole system charge fully, I was able to get several days of use out of the mouse without running out of energy. On a final note, in retrospective, it may have been easier to just buy the replacement battery pack, if it was available, as its cost is comparable to the cost of the four rechargeable batteries, but that would not be as much fun.

gyration-1.JPG gyration-2.JPG gyration-3.JPG

gyration-4.JPG gyration-5.JPG gyration-6.JPG

How to use a Smartmedia reader to read some NAND flash chips


BrandonU from uC Hobby has come up with a clever write-up on how to read a flash chip that is already in a circuit. The idea comes from the realization that Smartmedia cards are effectively flash chips and have compatible pinout with some industry standard NAND flash chips. The device must use 8-bit blocks and share an 8-bit wide I/O for both the address and data. This is by no means an end-all solution to reading flash chips, prostate but it may come in handy. The one part of the write up that may be problematic is inadvertently powering the board by providing power to the flash chip, pills but that can be looked at on a case-by-case basis.

[Via Hacked Gadgets]

How to make a rotary evaporator on a budget


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.

evap-01.JPG evap-02.JPG evap-03.JPG

evap-04.JPG evap-05.JPG evap-06.JPG

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( evap-action.AVI )

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


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.

usb-wifi-before.JPG usb-wifi-small-omni.JPG usb-wifi-after.JPG

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How to make your own Xilinx SPARTAN-3(E) board


Some time ago, I posted the schematics of Xilinx compatible parallel port to JTAG cables. Since then, I found more schematics that describe a complete Spartan-3 (or 3E) board including the same programming cable. These schematics include an FPGA (which can be as small as 100TQFP) and an SRAM chip with the intent of re-programming the setup at every powerup using JTAG. This can be extended by looking at page 67 of the V3.4 Spartan-3 datasheet. There are several methods of adding a configuration ROM to the device to ensure independent operation on power-up. Finally, the Xilinx ISE WebPACK can be downloaded to create basic bitmaps and actually send the code across providing a fairly limited, but free, development platform. Unfortunately, the Lattice Semi’s parallel port to JTAG cable is highly guarded proprietary information, so the same type of almost-free development solution is some ways off.

( livedesign_eb_schematics-xilinx_spartan.pdf )

Basic electronics primer from Tektronix


I just noticed that Tektronix has a special section on their website that is dedicated to aiding teachers with classroom and lab resources. They have some documents that are aimed at teaching people how to use their scopes, ailment whose contents can easily be applied generically to scopes from other vendors. They even have (a first in a series) pamphlets that are aimed to give a basic overview of some electrical engineering terminology. Although they are trying to sell their products, cheap the information contained is pretty universal. (Picture is from UMD.)

( 3gw_17276_0.pdf )

How to get root access on the Linksys WAP54G (v2)


One of the first uses for the rs232 line converter that I built last week was to access the serial port on a Linksys WAP54G that I have around. The board has a connector labeled J5 that has both power (+3.3V, link GND) and the UART0 pins available. After putting headers in the holes, cialis I was able to follow the pinout guide from Seattle Wireless:

 O O O O left to right: +3.3v +3.3v grnd grnd

O O O O O ttyS0 output, medicine  unknown, unknown, ttyS0 input, unknown

The com port setting is 115200 bps, 8N1, no flow control. The device shows a typical Linux bootup (included below) and goes straight to the root prompt (with the root fs mounted readonly). By holding down Ctrl-C while the device is powered up, the boot monitor can be invoked (also included below). So far, there is access to a pretty decent boot monitor, 2MB flash and 8MB ram. There is an unpopulated footprint for a second SDRAM chip on the back, where each should accommodate a 16MB chip bringing the total RAM on the board to 32MB. The flash might also be replaceable, but it would be difficult to recover the boot monitor without being able to program the TSSOP flash module, so that might be a bit harder. In any case, the next step for me is to modify the OS image and flash the device using tftp or the web interface.

( wap54gv2-linux.txt ) ( wap54gv2-cfe.txt )

How to look inside your (Linksys) firmware


Since I am not interested in shaping the Wii wireless network traffic further than I already have, I am moving on to modifying the provided Linksys firmware for the WAP54G access point. The very first step is to examine the filesystem to see what tools are available and how I might be able to hack a telnetd or something into it. The second step would be to download the sources from Linksys’ GPL code center.

After downloading the 2.08 firmware, we have a readme and a .trx file. The TRX file contains the kernel at the start and a cramfs (compressed ram filesystem) image at the end. The trick is to find the start of the cramfs image, and a good one to use can be found on this Seattle Wireless page. We look for the start of the cramfs magic number (3d4528cd), calculate the offset to it from the start of the file (0x0095f00 = 614144, add 12 for the offset to 0x3d45). Mounting the filesystem is pretty straightforward on a Linux sytem to read the contents. If you are too lazy to dedicate a machine, download the free VMware server, register it to get the serial code, download a Linux ISO and install it in a virtual machine. Most kernels come with cramfs pre-compiled and most systems with modest development tools will have hexdump.

( contents of the 2.08 WAP54G firmware: )