Archive for category Circuit Protoyping

DIRECT DIGITAL SYNTHESIS (DDS) EXPLAINED BY [BIL HERD]

One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the output of a counter that counts up to a maximum value and resets then the output of the DAC would be a ramp (analog signal) that increases in voltage until it resets back to its starting voltage.

This concept can be very useful for creating signals for use in a project or as a poor-man’s version of a signal or function generator. With this in mind I set out here to demonstrate some basic waveforms using programmable logic for flexibility, and a small collection of resistors to act as a cheap DAC. In the end I will also demonstrate an off-the-shelf and inexpensive DDS chip that can be used with any of the popular micro-controller boards available that support SPI serial communication.

All of the topics covered in the video are also discussed further after the break.

 

Read more at Hackaday.com

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BIL HERD: COMPUTING WITH ANALOG

When I was young the first “computer” I ever owned was an analog computer built from a kit. It had a sloped plastic case which had three knobs with large numerical scales around them and a small center-null meter. To operate it I would dial in two numbers as indicated by the scales and then adjust the “answer” by rotating the third dial until the little meter centered. Underneath there was a small handful of components wired on a terminal strip including two or three transistors.

Science Fair Analog Computer
Science Fair Analog Computer

In thinking back about that relic from the early 1970’s there was a moment when I assumed they may have been using the transistors as logarithmic amplifiers meaning that it was able to multiply electronically. After a few minutes of thought I came to the conclusion that it was probably much simpler and was most likely a Wheatstone Bridge. That doesn’t mean it couldn’t multiply, it was probably the printed scales that were logarithmic, much like a slide rule.

Analog slide rule on digital calculator
Old meets new: Analog and digital computation

Did someone just ask what a slide rule was? Let me explain further for anyone under 50. If you watch the video footage or movies about the Apollo Space Program you won’t see any anyone carrying a hand calculator, they didn’t exist yet. Yet the navigation guys in the first row of Mission Control known aptly as “the trench”, could quickly calculate a position or vector to within a couple of decimal places, and they did it using sliding piece of bamboo or aluminum with numbers printed on them.

 

Read more at Hackaday.com

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x64 Sagas – AVR Development and Programming

I just assembled the Ladyada Tiny ISP for AVR Atmel microcontrollers, http://www.ladyada.net/make/usbtinyisp/.  Easy to build, had my 10 year old son help with the soldering, only one burn to show for it.

You have to use a USBTiny with it and a COM bridge that simulates a null modem between two virtual com ports and have it emulate a null modem connection: Ladyada’s page did a reasonable job of leading through that: http://www.ladyada.net/make/usbtinyisp/stk500compat.html as an STK500 emulation.

Vista x64 requires digitally signed drivers and prior to SP1 you could disable this with the command

bcdedit /set loadoptions DDISABLE_INTEGRITY_CHECKS

This would appear to not work after SP1, I use the Driver Signature Enforcement Overrider (DSEO) available at http://www.ngohq.com/home.php?page=Files&go=cat&dwn_cat_id=34) Essentially you put the system into Test Mode and create a test signature for the driver. I now run with the text “Test Mode” in the corners of all four of my monitors.


Also ran into problems getting WinAVR to run correctly under Vista x64. Basically you need a new msys-1.0.dll and also I recommend not using the standard installation process as the special charcters “()” in the path Program Files (x86) cause conniptions with parts of the WinAVR app and compliation process. Thanks to MadWizard at http://www.madwizard.org/electronics/articles/winavrvista

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