Avalanche transistors can be used to generate fast rise time pulses. Their usage in the hobby world was made popular following an application note (AN72) by Jim Williams and was further publicized via this EEVBlog video. Many people have built such avalanche pulse generators for oscilloscope bandwidth measurements. In this post, I will show you the one I built using a general purpose BJT as well as some rise time measurements.
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I wrote a tutorial a while ago on how to hand solder fine pitched LGA/QFN chips using perfboards. While The technique illustrated works well with low pin count chips, for many people it is still a rather daunting task to solder these tiny chips that way. Also, as the pin count increases hand soldering without using a board with proper footprint becomes much harder.
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My seven year old 24 inch LCD monitor (Westinghouse L2410NM) started to flicker recently, so I decided to take a look inside to see what was wrong. Even before I opened it up, I had a pretty good idea of what might be the culprit. These older LCDs use CCFLs for back-lighting. CCFLs are typically quite robust. While it is not totally impossible, it is rather rare to see a failed CCFL. So most likely the issue is related to the power supply module.
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I bought an old Tektronix 2445 150 Mhz oscilloscope on eBay the other day. It was listed under “For Parts/Not Working” condition. Since the pictures in the auction listing suggested that the scope powers up and shows traces on all channels, I thought I would get it and fix it up.
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I did a teardown of a BK Precision 4011 5MHz function generator a few weeks ago. Like most of basic function generators in old days, BK 4011 does not offer frequency sweep as an option. What it does include is a VCG (Voltage controlled Generator) input, which essentially is just a VCO and it can be used in conjunction with an external sweep generator to generate frequency sweeps.
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The current sourcing/sinking capability of the I/O pins on Raspberry Pi is quite limited. According to the Wiki page, the current limit for each I/O block (e.g. GPIO0 through GPIO27 combined) comes at only 26 mA maximum, which is only capable of driving a couple of LEDs at a time. Also the I/O pins are 3.3V only, and going beyond the current or voltage limit could result in permanently damages to the chip.
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I got a used BK Precision 4011 5MHz function generator recently. The 4011 model is rather old and this particular unit was manufactured back in 1996. But BK precision still makes a similar model (4011A) which is identical to the older 4011 spec-wise except for the inclusion of an additional INV button for inverting the output waveform.
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Neal from SchmartBoard sent me an MSP430F5172 development board to check out. This board, according to the website, was co-designed with the University of Colorado for itw educational needs. It is actually just a breakout board for TI’s MSP430F5172 mixed signal microcontroller with added power regulator circuitry and a conveniently positioned JTAG connector.
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Last week, I discussed the construction of a network-capable temperature and humidity sensor using SHT21 and ENC28J60 with an ATmega328P microcontroller. In this post, I will show the results obtained so far and the techniques used to chart the data.
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I did a project on temperature/humidity logging a couple of years ago. In that project I logged the temperature and humidity readings in my basement lab over the course of a year. One issue with the approach I took back then was that the data could not be observed in real time because the logged data were written to an SD card and could only be retrieved once the logging process was done.
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Basic constant current dummy load using an Op Amp and a by-passing MOSFET is very easy to build and had been made quite popular following Dave’s video on EEVBlog. I happened to have an old aluminum hard disk cooler case collecting dust. The die-cast aluminum case is relatively thick, making it an excellent heat sink. So I thought why not use it to build a dummy load myself?
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In my earlier posts (1, 2, 3), I showed some examples of using the I2C protocol with TI’s MSP430 Launchpad. Many MCUs in the MSP430G2 family also support the SPI bus. In today’s discussion, I will give a couple of examples on communicating with an SPI port expander (MCP23S17).
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LM95172 is a 13 to 16 bits wide temperature range automotive-grade temperature sensor in a ceramic SOIC package. Besides its wide range temperature measurements capability (-40 Celsius to 200 Celsius), it can also be programmed to trigger over-temperature/under-temperature alarms and perform one-shot temperature conversation for low power applications.
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I got myself a Raspberry Pi (Model B V2) last month. After having played with it for a while, I have to say that I really like this tiny single-board computer. Since it runs on Linux, you can compile and run your C/C++ code on it. Most popular applications have already been adapted to the ARM architecture and can be run readily on Pi. Unlike some other SBCs, Pi allows easy access to GPIO ports which makes it equally attractive for people who are interested in hardware.
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A typical 3 ½ or 4 ½ multimeter can measure voltage in the low mV range and current in the low mA range. Voltage measurement in the µV range and current measurement in the nA range are typically only available in the more expensive lab bench multimeters. In this post, I will show you a simple adapter circuit that can be used for precision voltage measurement down to the µV range. Using this circuit along with the current adapter circuit I discussed earlier you will be able to perform most of the low level measurements with a 3 ½ meter.
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