Author Archives: DP

App note: P-channel power MOSFETs and applications

via Dangerous Prototypes

Another app note from IXYS on P-Channel power MOSFET application. Link here (PDF)

IXYS P-Channel Power MOSFETs retain all the features of comparable N-Channel Power MOSFETs such as very fast switching, voltage control, ease of paralleling and excellent temperature stability. These are designed for applications that require the convenience of reverse polarity operation. They have an n-type body region that provides lower resistivity in the body region and good avalanche characteristics because parasitic PNP transistor is less prone to turn-on. In comparison with Nchannel Power MOSFETs with similar design features, P-channel Power MOSFETs have better FBSOA (Forward Bias Safe Operating Area) and practically immune to Single Event Burnout phenomena. Main advantage of P-channel Power MOSFETs is the simplified gate driving technique in high-side (HS) switch position.

App note: Parallel operation of IGBT discrete devices

via Dangerous Prototypes

Guidelines for parallel operation of IGBT devices discuss in this app note from IXYS. Link here (PDF)

As applications for IGBT components have continued to expand rapidly, semiconductor manufacturers have responded by providing IGBTs in both discrete and modular packages to meet the needs of their customers. Discrete IGBTs span the voltage range of 250V to 1400V and are available up to 75A (DC), which is the maximum current limit for both the TO-247 and TO-264 terminals. IGBT modules cover the same voltage range but, due to their construction, can control currents up to 1000A today. However, on an Ampere per dollar basis, the IGBT module is more expensive so that for cost-sensitive applications, e.g. welding, low voltage motor control, small UPS, etc., designs engineers would like to parallel discrete IGBT devices.

cVert, a truly random MIDI controller

via Dangerous Prototypes

cVert, a truly random MIDI controller @ danny.makesthings.work

cVert is the result of an idea I’ve been kicking around for years, and took a few months of work to bring to fruition. The idea was to use a Geiger counter as a true random number generator to give a non-deterministic input for computer art or music. The result is a MIDI controller with a large amount of control removed – it plays a random musical note every time a radioactive decay is detected.

All files are available on GitHub.

Check out the video after the break.

DIY home made portable oscilloscope

via Dangerous Prototypes

An ATmega328 based portable home made oscilloscope with ADC from Creative Engineering:

It is basically a small scaled digital oscilloscope. It is capable of displaying all type of waveform like sine, triangular, square, etc. It’s bandwidth is above 1 MHz and input impedance is about 600K. The device is mainly using the ATmega328 micro-controller as the heart and is assisted by a high performance ADC (TLC5510) which is capable of taking up-to 20 mega samples per second and thus increasing the span of bandwidth which can be analyzed by our device. In addition to that, in-order to make the device portable Li-ion battery is used , which will be suitable to be fitted into a confined space.

See project details on Creative Engineering blog.

Check out the video after the break:

Repairing an HP 3438A digital multimeter

via Dangerous Prototypes

Jeff (aka K6JCA) did a repair of an HP 3438A digital multimeter and documented the whole process on his blog:

This blog post is a record of my notes made while repairing an HP 3438A Digital Multimeter I had picked up last year at a local electronics swap meet. The 3438A is a 3.5 digit HP-IB controllable multimeter. It has five selectable functions: DC Volts, AC Volts, DC Amps, AC Amps, and Ohms. Of these five functions, three can be auto-ranged: DC Volts, AC Volts, and Ohms.

Extracting ROM constants from the 8087 math coprocessor’s die

via Dangerous Prototypes

Ken posted an article taking a closer look at Intel 8087 chip:

Intel introduced the 8087 chip in 1980 to improve floating-point performance on the 8086 and 8088 processors, and it was used with the original IBM PC. Since early microprocessors operated only on integers, arithmetic with floating-point numbers was slow and transcendental operations such as arctangent or logarithms were even worse. Adding the 8087 co-processor chip to a system made floating-point operations up to 100 times faster.
I opened up an 8087 chip and took photos with a microscope. The photo below shows the chip’s tiny silicon die. Around the edges of the chip, tiny bond wires connect the chip to the 40 external pins.

More details on Ken Shirriff’s blog.