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.

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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.

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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.

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