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User Interface
Mon, Jul 27 2009 11:13
Strictly speaking, the EPCS main function of toggling valves at set intervals doesn't require any user input, and it's likely to be quite some time before an algorithm is embedded to provide real-time results, so a display is also not necessary, but a device without a user interface is an inflexible one. The development and debugging process will also... Read More...
by Ben Voigt | with no comments
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Common-cathode LEDs suck
Mon, Jul 27 2009 2:05
Or sink. Whatever. No matter which word you use, there's a need for the logic to source a current of 25mA (or reasonably close). I definitely prefer LED banks with anodes tied to the positive power rail. NPN and NFET transistors are more efficient per unit area than their PNP or PFET counterparts, so interfacing LEDs usually can be done using microcontroller... Read More...
by Ben Voigt | with no comments
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Schematic of JTAG and serial-over-USB
Tue, Jul 14 2009 23:37
As previously mentioned , the EPCS will take advantage of the FTDI FT2232H USB-serial converter and its integrated multi-protocol synchronous serial engine (MPSSE) support for JTAG for programming and debugging the ADuC7025 firmware. The second serial port provided by the FT2232H will be used in UART mode to provide a link for streaming data back to a PC. I envision... Read More...
by Ben Voigt | 1 comment(s)
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JTAG Programming/Debugging Adapter
Mon, Jul 13 2009 0:08
Having a microcontroller in an embedded project doesn't do much good until you are able to program it, because in contrast to fixed-function ICs or configurable ICs with reasonable defaults, microcontrollers have little to no useful behavior from the factory. Some families of microcontroller, like the Z-World Rabbit or Microchip PIC , have unique programming... Read More...
by Ben Voigt | with no comments
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Is that Instrumentation Amplifier needed?
Sun, Jul 12 2009 19:54
While writing the post on selection of the microcontroller , I got a little deeper into the capabilities of the integrated ADC peripheral. Initially I had just been relying on past experience with Analog Devices ICs for assurance that if the basic specs were sufficient then my needs would be met. But now I've discovered that the ADuC7025 ADC provides adjustable... Read More...
by Ben Voigt | with no comments
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Processor
Sun, Jul 12 2009 18:57
A while back one of the embedded design newsletters I receive mentioned a kind of "super-ADC", barely more expensive than the usual ADC and about the same size but with a microcontroller embedded (for example, the ST7FOX , S08QD , AVR ATtiny25 , and P89LPC90x are all 8 pins, while the AVR ATtiny10 has 4 ADC channels in only 6 pins), allowing for programmable... Read More...
by Ben Voigt | with no comments
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Pneumatic Actuator
Sat, Jul 11 2009 17:44
Since the whole purpose of the EPCS is to mitigate the need for a human to turn two stopcocks twice per minute, we need to replace the stopcocks with electric control and that means an solenoid pneumatic valve. The arrangement of the stopcocks was such that one port needed to communicate with either of two pressure reservoirs, thus a single 3-way valve is sufficient... Read More...
by Ben Voigt | 2 comment(s)
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Signal Conditioning
Fri, Jul 10 2009 20:31
Blood pressure is one of the better known vital signs, measured by just about everyone, often with a non-invasive blood pressure cuff. But the cuff is inaccurate, yields only one measurement per cycle (approximately 60 seconds) and causes tissue damage if inflated too often, so for critically ill patients and in animal experiments blood pressure is recorded continually... Read More...
by Ben Voigt | with no comments
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A Battery's Raison d'être
Thu, Jul 9 2009 23:32
Yesterday I put you all on notice that this embedded pneumatic control system (henceforth EPCS) will be battery-powered, gave an bunch of reasons that are inapplicable to this system, and promised to reveal the true reason today.  I also hinted smugly that the decision involved safety somehow.  Readers of The Hitchhiker's Guide (nope, no commissions... Read More...
by Ben Voigt | with no comments
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Greetings
Wed, Jul 8 2009 22:08
After much avoidance I've decided to start a blog.  Ok, maybe the fact that one of my mentors told me that applying for a Professional Engineer license requires submitting narratives about project design almost exactly like a blog had something to do with it.  But I'd never admit to something like that, doesn't it sound unlikely to you too... Read More...
by Ben Voigt | 2 comment(s)
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