Get To Know 3½ Digit ADCs With The ICL71xx

January 31, 2017 by Anool Mahidharia 29 Comments

Riffling through my box of old projects, I came upon a project that I had built in the 80’s — an Automotive Multimeter which was published in the Dutch/British Elektor magazine. It could measure low voltage DC, high current DC, resistance, dwell angle, and engine RPM and ran off a single 9V battery. Besides a 555 IC for the dwell and RPM measurement and a couple of CMOS gate chips, the rest of the board is populated by a smattering of passives and a big, 40 pin DIP IC under the 3½ digit LCD display. I dug some more in my box, and came up with another Elektor project from back then — a True RMS digital Wattmeter with a 3½ digit LCD display that could measure up to 2kW. It had the same chip too. Some more digging, and I found a digital panel meter. This had a 7 segment LED display, but the chip was again from the same family.

Look under the hood of any device with a 3½ or 4½ digit, 7 segment, LCD or LED from the ’80’s or ’90’s and you will likely spot this 40-pin DIP with the Intersil logo (although it was later also manufactured by many other fabs; Harris and Maxim among others). The chip doing all the heavy-lifting was likely to be the ICL7106 or ICL7107. These devices were described as high performance, low power, 3½ digit A/D converters containing seven segment decoders, display drivers, voltage reference and clock. In short, everything you needed to take a DC analog signal and display it. Over time, a whole series of devices were spawned:

7106 – 3½ digit, 7 segment LCD
7107 – 3½ digit, 7 segment LED
7116 – 3½ digit, 7 segment LCD, with display HOLD (freeze)
7117 – 3½ digit, 7 segment LED, with display HOLD (freeze)
7126 – improved 7106
7136 – improved 7126
7135 – 4½ digit, 7 segment LCD

There were many similar devices available, but the ICL71xx series was by far one of the most popular, due to its easy of use, low parts count and single chip implementation. Here are several parts (linking to PDF datasheets) to illustrate my point: the TC14433/A needed several peripheral devices, ES5107 (a clone of a clone — read below), CA3162 (which has BCD output, and needs the CA3161 or similar to interface to a display), or the AD2020 (which too needed a lot of support circuitry).

The ICL71xx was the go-to device for a reason. Let’s take a look at the engineering and business behind this fascinating chip.

Continue reading “Get To Know 3½ Digit ADCs With The ICL71xx” →

Your Arm Is The Ideal Controller

January 31, 2017 by James Hobson 25 Comments

With interest and accessibility to both wearable tech and virtual reality approaching an all-time high, three students from Cornell University — [Daryl Sew, Emma Wang, and Zachary Zimmerman] — seek to turn your body into the perfect controller.

That is the end goal, at least. Their prototype consists of three Kionix tri-axis accelerometer, gyroscope and magnetometer sensors (at the hand, elbow, and shoulder) to trace the arm’s movement. Relying on a PC to do most of the computational heavy lifting, a PIC32 in a t-shirt canister — hey, it’s a prototype! — receives data from the three joint positions, transmitting them to said PC via serial, which renders a useable 3D model in a virtual environment. After a brief calibration, the setup tracks the arm movement with only a little drift in readings over a few minutes.

Continue reading “Your Arm Is The Ideal Controller” →

DIY Roll Bender Keeps It Simple And Sturdy

January 31, 2017 by Dan Maloney 28 Comments

If you’ve ever tried to bend a metal pipe or bar over your knee, you’ll know that even lightweight stock requires quite a bit of force. And the force needs to be properly directed, lest the smooth bend you seek become a kink or a crease. When your hands and knees no longer fill the bill, try [MakeItExtreme]’s sturdy and simple roll bender.

As we watched the video below, we had a little déjà vu — hadn’t the [MakeItExtreme] crew built a roll bender for their shop before? Turns out they had, but in reviewing that video, we can see why they gave it a second shot. This build is a model of simplicity compared to the previous. With a frame fabricated from just a few pieces of steel I-beam, this version is far more approachable than its big brother and just about as capable. The three forming rollers ride in stout pillow blocks and can be repositioned for different bending radii. A 2-ton hydraulic bottle jack provides the force needed to direct the stock through the rollers, which are manually powered. In a nice touch, the incomplete tool was used to create the rim of the large-diameter handwheel for the drive roller.

The tools keep piling up at [MakeItExtreme]’s open air workshop — we even get a glimpse of their heavy-lift electromagnet that we recently featured. As always, we love the fit and finish on these builds, and watching the time-lapse videos is like a condensed class in metalworking.

Continue reading “DIY Roll Bender Keeps It Simple And Sturdy” →

GSM Sniffing On A Budget With Multi-RTL

January 30, 2017 by Elliot Williams 26 Comments

If you want to eavesdrop on GSM phone conversations or data, it pays to have deep pockets, because you’re going to need to listen to a wide frequency range. Or, you can just use two cheap RTL-SDR units and some clever syncing software. [Piotr Krysik] presented his work on budget GSM hacking at Camp++ in August 2016, and the video of the presentation just came online now (embedded below). The punchline is a method of listening to both the uplink and downlink channels for a pittance.

[Piotr] knows his GSM phone tech, studying it by day and hacking on a GnuRadio GSM decoder by night. His presentation bears this out, and is a great overview of GSM hacking from 2007 to the present. The impetus for Multi-RTL comes out of this work as well. Although it was possible to hack into a cheap phone or use a single RTL-SDR to receive GSM signals, eavesdropping on both the uplink and downlink channels was still out of reach, because it required more bandwidth than the cheap RTL-SDR had. More like the bandwidth of two cheap RTL-SDR modules.

Getting two RTL-SDR modules to operate in phase is as easy as desoldering a crystal from one and slaving it to the other. Aligning the two absolutely in time required a very sweet hack. It turns out that the absolute timing is retained after a frequency switch, so both RTL-SDRs switch to the same channel, lock together on a single signal, and then switch back off, one to the uplink frequency and the other to the downlink. Multi-RTL is a GnuRadio source that takes care of this for you. Bam! Hundreds or thousands of dollar’s worth of gear replaced by commodity hardware you can buy anywhere for less than a fancy dinner. That’s a great hack, and a great presentation.
Continue reading “GSM Sniffing On A Budget With Multi-RTL” →

Hacking Together A Serial Backpack

January 30, 2017 by Elliot Williams 30 Comments

A serial backpack is really nothing more than a screen and some microcontroller glue to drive it. And a hammer is nothing more than a hardened weight on the end of a stick. But when you’re presented with a nail, or a device that outputs serial diagnostic data, there’s nothing like having the right tool on hand.

[ogdento] built his own serial backpack using parts on hand and a port of some great old code. Cutting up a Nokia 1100 graphic display and pulling a PIC out of the parts drawer got him the hardware that he needed, and he found a good start for his code in [Peter Andersen]’s plain-old character LCD library, combined with a Nokia 1100 graphic LCD library by [spiralbrain]. [ogdento] added control for the backlight, mashed the two softwares together, and voilà!

A simple screen with a serial port is a great device to have on hand, and it makes a great project. We’ve seen them around here before, of course. And while you could just order one online, why not make your own? Who knows what kind of crazy customizations you might dream up along the way.

Sticking With The Script For Cheap Plane Tickets

January 30, 2017 by James Hobson 27 Comments

When [Zeke Gabrielse] needed to book a flight, the Internet hive-mind recommended that he look into traveling with Southwest airlines due to a drop in fares late Thursday nights. Not one to stay up all night refreshing the web page indefinitely, he opted to write a script to take care of the tedium for him.

Settling on Node.js as his web scraper of choice, numerous avenues of getting the flight pricing failed before he finally had to cobble together a script that would fill out and submit the search form for him. With the numbers coming in, [Grabrielse] set up a Twilio account to text him once fares dropped below a certain price point — because, again, why not automate?

Continue reading “Sticking With The Script For Cheap Plane Tickets” →

SDR And Node.js Remote-Controlled Monster Drift

January 30, 2017 by Elliot Williams 9 Comments

Most old-school remote controlled cars broadcast their controls on 27 MHz. Some software-defined radio (SDR) units will go that low. The rest, as we hardware folks like to say, is a simple matter of coding.

So kudos to [watson] for actually doing the coding. His monster drift project starts with the basics — sine and cosine waves of the right frequency — and combines them in just the right durations to spit out to an SDR, in this case a HackRF. Watch the smile on his face as he hits the enter key and the car pulls off an epic office-table 180 (video embedded below).

Continue reading “SDR And Node.js Remote-Controlled Monster Drift” →