Using electrolysis on this leatherman skeletool brought it back from the dead. The tool was lost two years ago while wendy was planting trees. It slipped out of her overalls and we were unable to locate it. While planting trees this week the tool was found in unusable condition. I put it into a bath with a chunk of metal and connected it to a irobot roomba 22V battery charger. Within two days the tool was working again.
These are great for doing a little heavy lifting with a microcontroller. Most micros can only source or sink about 20mA of current with each pin. If you’re trying to do something like drive a high-power multi-segment LED display, the current from a microcontroller pin just won’t cut it. You could run the micro outputs in parallel for more current, but then you lose pins for other purposes. Using an external array for the switching lets each pin drive a unique load at higher current, with the added benefit of offloading some of the heat from the microcontroller.
The ULN2003/4 and ULN2803/4 are 7- and 8-element Darlington arrays which can switch up to 500mA (MAX!) per channel at up to 50 volts. Channels can be combined to switch higher current loads (still 50V though). Take note of that “500mA MAX”: while the 2×03′s can switch that much current, they can’t do it forever, because they can’t dissipate the heat. The total amount of switchable current will depend on the number of channels you’re driving at the same time, and the duty cycle of the input signal. See the datasheet (PDF) for more information.
The 2xx3 chips have 2.7k input resistors, so they can be driven from a 5V TTL/CMOS line – if you’re using an Arduino, you should get the ULN2003/2803. The 2xx4 chips have 10.5k resistors for inputs of 6-15 volts.
These are great for driving multiple RGB lines with lots of LEDs, or a bank of relays or motors (they have clamp diodes built in!). The following illustrates how to properly connect the ULN for driving an inductive load like a DC motor.
Purchasing note: these chips were originally (and still are) made by TI. The TI chips are great, but recently I noticed Mouser has begun carrying the Toshiba versions for about 30% less cost. I’ve used both, and they perform equally well.
Every piece of clothing has a story: There’s far more to a $155 polo shirt than a yard of fabric, four buttons and a length of thread.
The tale of a KP MacLane polo shirt offers a rare look inside the planning and global transactions behind the clothes people wear. To begin, though, there is an actual KP MacLane—Katherine, who founded the brand with her husband, Jared MacLane.
Manufacturing clothing, surprisingly similar to electronics – finding the right suppliers, fab house, making hundreds of decisions.
The recent discussion about the “new” 6502 from WDC got me thinking about other old and/or unavailable chips that could use a re-introduction, or perhaps just a process facelift. This post is mainly to solicit reactions and suggestions from viewers like you, but I’ll provide my own example too.
Having recently gotten back in to analog synth design after a long hiatus, I was rather shocked to discover that OTAs (operational transconductance amplifiers) suited to such work are few and far between. With the exception of the NE5517 and the LM13600/13700, there are no other audio OTAs currently in production. TI (via BurrBrown) manufactures other OTA devices, such as the OPA860/861, but these are optimized for high-speed analog (RF and transmission line) and they are rather expensive. For many synthesizers, the OTA forms the heart of nearly every voltage-controlled module and using them greatly simplifies the process vs. building with discrete components (such as a Moog ladder). The best OTA for audio was probably the CA3280, which is sadly no longer in production, due to the process becoming obsolete, among other factors. This 2005 blog post by Don Tillman, which explains the whole problem perfectly, was part of the inspiration for this blog post, and I’m going to throw in with Don and humbly request that someone please update the CA3280 to the latest fab, give it 21st-century specs, and bring it back into production.
If the 3280 is a no-go, for whatever reason, then my second choice would be an update of the LM13700 (originally from National). The LM13700, which was designed by Don Blake, is currently available from both National and NJR, but it’s got its problems. It’s somewhat noisy, for one. It also has an output offset current which scales with the transconductance (a problem when building integrators), and the buffer is just a simple darlington pair. It would be great (read: totally awesome!) if someone were to update the chip to a BiCMOS process, while changing the design to drop the noise floor and increase the dynamic range, reduce the output offset current and replace the darlingtons with FET-input opamps. This might sound like a very involved request, but the expertise is already there to do it — analog devices have come a long way in 30+ years, and the basic design of the 13700 is not very complex, compared to modern opamps.
In case you’re wondering what incentive there is for somebody to do this, I submit that, compared to when I was doing it 10+ years ago, there’s A LOT more information out there now about DIY synths, and the increase in homebuilt synth projects has paralleled the increase in DIY ‘tronix in general. There’s definitely a willing (and growing) market for these things, and with a chip redesign they could certainly charge more per chip. There’s also a resurgence in analog electronic music in general right now, which means these new chips may find their way into commercial products as well.
So anyway, that’s my request. I suspect there are lots of different opinions on the subject, however. If you have a chip you’d like to see resurrected and brought back into production, or just updated to modern spec, post it in the comments! Try to include some info with your suggestion, and reasons why you think such an update would be successful.
Overview:
Laying out the circuit board is one of the last steps in the design process and quite often doesn’t get the attention it deserves, and high speed applications can significantly affect circuit performance if not done correctly. This webcast will cover the ins and outs of PCB design and layout, in a practical and straight forward approach. The presentation is packed with useful information accumulated with tips, tricks and techniques that can easily be implemented into your next design to help improve overall circuit and system performance.
Who should attend?
This webcast is a “must see” for students and those new to PCB design, especially for those concerned with high-speed circuitry. It will also be a good refresher to those experienced in layout.
New York’s got an abundance of almost everything, but engineers are increasingly a precious commodity. But the NYC Turing Fellows Program is revving up in its second year to really take on the problem and start feeding more tech talent to the exploding startup scene.
The Turing Fellows Program last summer placed 19 college interns out of 750 applicants at New York startups including Tumblr, Foursquare and others. Now, the paid internship program is expanding, and will place around 25 to 30 engineering, mathematics or computer science students at startups this summer. The application process, which quietly began earlier this month closes on Feb. 6.
The program is co-organized by Canaan Partners, FirstMark Capital, Tribeca Venture Partners and First Round Capital. This year’s crop of startups include Etsy, Second Market, BuzzFeed, Blip and many others. Other supporting partners include Amazon, SV Angel, David Tisch of New York TechStars, Silicon Valley Bank, and Esther Dyson, along with the New York City Economic Development Corp. and the New York City Investment Fund.
…He said the program tried to pick a diverse group of startups that spanned advertising, mobile, e-commerce and financial technology to give students different opportunities.
Great idea, and a great start. Looks like there are not any hardware companies, maybe next year
8-voices mixed in the micro, with nothing on the output but an RC integrator.
What the heck is a “Fraunchpad”? Well, it’s similar to the Launchpad, but with FRAM (Ferroelectric RAM, not an oil filter). Specifically, it’s the MSP-EXP430FR5739. The song data is stored in the FRAM.
A big part my New Year’s Resolution to improve my overall design process was better testing. Better testing is an important part of better and more intentional design, but it means having tools that you can trust and that can consistently give you the results you need.
While I’ve built up a decent little collection of toys over the years, I spent quite a bit of time late 2011 figuring out what I wanted to add or replace on my workbench in 2012 to be able to improve projects I’m working on. At the top of the list was a faster mixed-signal oscilloscope, followed by a more reliable bench-top multi-meter, and a decent function generator rounding the big ticket items out.
After spending quite a bit of time selecting a scope that matched my budget and requirements, and looking (importantly!) at the ecosystem around that scope, I settled on Agilent’s new MSOX2000/3000 series — specifically, the Adafruit Christmas Elves picked out an MSOX2024a (the screenshot above was taken on this scope). These scopes (in my opinion) are an excellent value for a mid-range scope, and really raise the bar for the competition in the $2-5K range. I’d like to write a few blog posts on the reason behind that choice and the thinking behind the whole list of items above, but as a first foray into that I thought I’d try to explain some of the details you should keep in mind if you’re thinking about a scope yourself (probably the most useful tool on any EEs workbench after a multimeter).
The most obvious factor when choosing an oscilliscope is bandwidth. 50MHz is better than 20MHz, and 100MHz is definitely better than 50MHz, etc., but what does that number really mean, and how fast is fast enough for your needs? There are already some good resources out there that go into exhaustive details on this … but for the executive summary read on. (more…)
An ever-present challenge in electronic circuit design is selecting suitable components that not only perform their intended task but also will survive under foreseeable operating conditions. A big part of that process is making sure that your components will stay within their safe operating limits in terms of current, voltage, and power. Of those three, the “power” portion is often the most difficult (for both newcomers and experts) because the safe operating area can depend so strongly on the particulars of the situation.
In what follows, we’ll introduce some of the basic concepts of power dissipation in electronic components, with an eye towards understanding how to select components for simple circuits with power limitations in mind.
Interesting news for chiptune and 8-bit folks — the 6502 is back! From h-online:
The 6502 processor from the 1970s is alive once again – and as a proper 40-pin chip in a dual in-line package (DIP) housing, not just as an embedded core. Mouser Electronics has added the 8-bit classic, since modernised by WDC(Western Design Center), to its product range, making it available in the UK for £4.90.
Apparently, the W65C02S6TPG-14 – its current name – is pin and software compatible with its grandfather, a 1975 drawing board design by Bill Mensch and Chuck Peddle that was later used in the early Apple and Commodore computers as well as the UK’s own BBC Micro. Like other members of the 6502 family, the W65C02S6TPG-14 offers an extended set of instructions and a clock speed of up to 14 MHz (instead of the original 1 MHz). Incidentally, WDC also offers a “virtual” version of the 65C02: an IP core designed for field-programmable gate arrays (FPGAs).
It’s currently selling at Mouser US for $7, which sounds a bit steep for a 30+ year old 8-bit micro design, but I have no idea what the production volume is.
It seemed so simple. The best ideas always do. However, sometimes the smallest problems end up taking the most time to solve. There was some swearing, I won’t lie.
You see, I had a really swell circuit that could take a ROM image and dump it into an SRAM. Since parallel EEPROMs exist that are accessed just like SRAMs, I figured I could just buy one, drop it in, and presto- ROM for Veronica. Flawless plan, right?
Well, a hundred hours or so later, it turns out the plan was in fact pretty darn solid, but the parts were against me. To recap, I designed a board for Veronica that would hold an EEPROM chip, and had a built-in ATTiny that acted as an interface between the EEPROM and my USBTinyISP programmer. Since EEPROM programmers are very expensive, this was a way to leverage the tools I had to program the ROM that Veronica needs to boot up.
David Clift-Reaves has created MezzoMill, a PCB router which can provide custom single-sided PCBs in short order. He’s currently running a kickstarter to get the project into production. He writes:
The conversation that I had hoped that MezzoMill would help to shine a light on is the need for individuals, hackerspaces, and schools to have small-scale electronics manufacturing facilities. I believe that there are 3 key technologies that are necessary to a modern electronics fab. First is the ability to print circuits. Second is the ability to place modern components on the circuit. Finally, the third is the ability to do reflowing.
Like the iBooks Author program, I feel that these disruptive technologies have the ability to empower people and transform an industry. Clearly all of the technologies already exist for creating these machines. People hack together various versions of them all the time. There needs to be work done towards mass producing them and a guiding vision for making all of them work together seamlessly.
I designed the MezzoMill to simplify the problem of printing circuits. It turns the experience of printing circuits from EAGLE to one like from your word processor to your inkjet. It makes the process safe and repeatable while reducing the user interaction with the process as much as possible. It is the only solution in its price range that provides this user experience to individuals.
Very cool! I see hacks all the time where people have put together PCB routers using gantry dremels and the like, but the focus here is on self-contained, user-friendly repeatability and flexibility. That’s something which a lot of home builds lack — not intentionally, mind you, but they are built by users for themselves and require less generalization. I think a general machine designed for a wider user base is the next logical step.
Printable catalog (PDF)
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