All posts by Pete Soper

CAD/CAM, Tools

EveryCircuit: Chrome killer app for electronics enthusiasts

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everycircuit.com-circuit-6343833974472704-full-wave-rectifier-

I recently added an app to my smart phone and, as a side effect, added another app, and  that led me to stumble upon the web site http://everycircuit.com, which provides electronic circuit editing/simulation/presentation tools together with commercial and crowd sourced example circuits.

For those whose religious convictions or practical circumstances make Chrome available on a laptop/desktop, the rest of this page might be interesting. Likewise, if you have a spare $10 the Android or IPhone apps might be interesting. So far, the Android version “just works” on my phone and I personally rate it “Uh, I’ve got to put my socks back on.”  Finally reading the site’s terms of use use might be a good idea for some people. I carefully read every word, something I rarely do. But I was relieved to see that the EveryCircuit people (currently) appear to stop short of claiming copyright on crowd sourced circuits.

To check this site out, try this link to the user-submitted rectifier circuit example above inside an instance of the Google Chrome browser on a desktop or laptop computer:

Visit rectifier example

Now  click the moving squiggle in the upper left. It expands to a pretend oscilloscope showing voltage and current vs time for one part of the circuit.

Now click the “edit this circuit” link. There are tools for modifying this circuit.

Cool, heh? The main site page is here.

Yes, again, this tool isn’t supported in many, many settings that readers of this blog find themselves in. It’s completely dependent on Chrome.  On behalf of the company owning this site (that I just found: I have no connection to it), I’m sorry it isn’t more portable.

By the way: Anybody reading this is welcome to submit their impressions of this or anything else here as comments below. TriEmbed meeting attendees or their online friends (such as in Vermont) are invited to request a blog account if they have interest in adding content to this site via blog postings, additional project pages, etc. Your access  will be proportional to how well you’re known to the admins and editors (but we’re always looking for new editors and at least one additional admin!) It takes about 10 minutes with somebody who is WordPress fluent to learn how to add content.

CAD/CAM, Device Characterization

Low Voltage MOSFET Transistors

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Shane Trent recently shared some recommendations for MOSFET transistors in SOI8 packages that will switch to saturation with ordinary logic level signals.  The two transistors he mentions are inexpensive, offer low on resistance, and would seem to be perfect for prototyping, except for one detail. Off the shelf SOIC8 breakout boards such as this one from Adafruit are designed for small signals and modest power supply currents. The N channel part Shane recommends can handle enough current in pulse mode to demonstrate the Adafruit board traces as fusible links. On the other hand, anything beyond a small number of amperes is asking trouble with a breadboard. (For higher power situations Shane’s article also describes interesting transistors in TO220/251 packages.)

After kicking some ideas around a simple breakout board was designed to cover both low-medium and high current use cases. A handful will be coming from OSH Park within the next couple weeks. Here are top and bottom views of the board:

PowerFetSOIC8-1-topPowerFetSOIC8-1-bottom

Assuming it has no CAD or fabrication bugs, this board will handle any SOIC8 FET with the pins 1-3 for Source, 4, for gate, and 5-8 for drain. The resistor R1 connects the gate to the source to avoid accidental triggering from high Z or open circuit situations.  A value of one megohm should be sufficient. The pads are for an 0805 size resistor. The bottom three pads are for standard or right angle male header pins to go into a standard breadboard. The upper pads are sized for 16 gauge wire to allow high current connections to the source and drain.

Some assembled and bare boards will be brought to the July 13 TriEmbed meeting at NCSU. If the first version is defective we’ll use them to play tiddlywinks. As soon as the board is shown to have no defects the design will be published to the OSH Park “Shared Project” area on their web site.

 

Device Characterization, Tools

Open standard for connector/wire-free charging adopted by major car manfacturers

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Open Dots Compatibility Logo

 

Ford, Chrysler, RAM, Dodge, and Scion have embraced an open standard for conveniently recharging portable devices that appears to be more effective and just easy to use as inductive charging systems. It’s called Open Dots.

The basic idea is to use a set of four parallel conductive strips to carry positive and negative voltages (or +V and ground, depending on your point of view) and have the package of a device to be charged connect to the charging strip automagically just by resting on it. The device to charge has a pattern of four conductive “dots” on its case that will properly connect with the charging pad in any orientation. This scheme was invented for recharging toys in 1963.

I’m sharing this as a potentially handy way to deal with the general problem of recharging battery-operated gadgets. It would take a fair amount of work to implement the pieces and parts involved with the actual electrical connections, but based on  the specification this is on the other end of the scale from rocket science and one would hope that the basic components may be or become cheaply available if the auto industry is involved .

As far as I can tell from their web site anybody could freely use these circuits and connector specs without consequences. (In order to sell something using the Open Dots logo one would need to execute and abide by a member agreement. But you do not need to get within a mile of this logo and could simply use the specs and reference circuits freely until you start selling a ton of stuff and see an advantage to becoming “official”.)

(Open Dots logo used without permission.)

Device Characterization

TI Regrooves the MSP430?

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(This is the moral equivalent of a press release that is not based on anything remotely official from TI. I know NOTHING beyond what I’ve read about this subject along with a smattering of MSP430 experience. I’m sharing this because I think it might be of interest to the TriEmbed community.)

Texas Instruments has introduced a new family of microprocessors called the MSP432.  As far as I can tell they’ve combined the very sophisticated power saving modes and mature peripheral functional blocks of the MSP430 family with an ARM M4F core.  I’m writing this because the initial chips are available in a QFP package.

The initial chips come with a couple of generous flash memory/RAM sizes combinations and run at 48mhz. Claimed integer MIPS/MHz are substantially higher than with the MSP430 and current consumption from the datasheet is only 90uA/MHz. But these are probably marketing MIPS and most assuredly marketing microamperes, as they understandably assume little or no peripheral subsystem activity. (Take it from me, you can get any result you want from the Dhrystone benchmark with a good compiler).  Still, to the extent that the MSP430’s programmatic support for low power modes is present in spades with a new “power manager” function, and the fact that the chips come with ROM-code peripheral libraries to make porting from the 430 easier, this seems to be an interesting development. I view this as a smart, if not surprising move by TI.

Additional info:

TI Info page

MSP432P4xx Technical Reference Manual

MSP432P401x Mixed Signal Microcontrollers Data Sheet

Device Characterization, Tools, Where to get stuff

Alternative short distance rangefinder: measures light transit time, not reflection angle

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Here’s a device available on a pair of Sparkfun boards that Rod pointed us and Triangle Amateur Robotics to:

http://datasheet.octopart.com/VL6180XV0NR-1-STMicroelectronics-datasheet-26529471.pdf

Update from Rod: A sensor + ARM M4 eval board for $20 from the chip maker:

 http://www.mouser.com/ProductDetail/STMicroelectronics/EVALKIT-VL6180X/?qs=sGAEpiMZZMvfpQN6QVmrfGjb{13079d06258ef9010cea88dee32f3cdfc6f216a54651010f7303ce6140ee927c}252b49cDybCa83Lgq8kEXU{13079d06258ef9010cea88dee32f3cdfc6f216a54651010f7303ce6140ee927c}3d

Happenings

Teaching Microcontroller Programming to Middle Schoolers Inexpensively

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February 9th TriEmbed Meeting at NCSU

 This month’s meeting will have a highly focused theme: Tools and techniques for teaching middle school age children without spending a wad on hardware. There will be two speakers:
  • Alan Smith will bring examples of the boards related to his  Wizarding 101 and 102 classes for middle schoolers and will focus on what he’s  learned teaching introduction to microcontrollers from these classes as well as a full course.
  • Jon Wolfe of Anibit will talk about a graphical programmer he’s been developing.

More details, directions, etc on the “Meetings at NCSU” page.