inductance

23 Articles

Measuring SMD Parts With A Home Brew Version Of Smart Tweezers

November 7, 2012 by 22 Comments

SMD parts are great; they allow you to pack more parts on a board, do away with drilling dozens of PCBs, and when done correctly can produce a factory-quality board made in a home lab. There’s one problem with SMD parts; troubleshooting and measuring them. The ideal solution would be something akin to the Smart Tweezers we’ve seen before, but this fabulous tool costs three hundred bones. [Kai] came up with a much cheaper solution: home brew smart tweezers that can be built for a tenth of the cost as the professional model.

What [Kai] built is an LCR meter, basically a tool that measures inductance, capacitance, and resistance in a very, very small form factor. The technique of measuring a part’s properties involves feeding a set frequency into the device and measuring the phase, voltage and current coming out. It’s all wonderfully explained by [Dave] over at EEVblog in one of his earlier videos.

The hardware [Kai] is using includes an LCD display from a Nokia phone, an MSP430-based microcontroller, a very tiny opamp near the tip of one of the points of the tweezer, and a programmable gain amplifier used to measure the components. In testing, [Kai] can measure very low-value components with a +/- 2% accuracy, and larger, more realistic components with +/- 0.25% accuracy. An awesome accomplishment, and much better than the common Chinese meters that can’t measure in the nH/pF/mΩ range.

[Kai] hasn’t gotten his pair of smart tweezers working yet – he still needs to get the circuit up and running and write some software. We’ll keep our readers apprised of [Kai]’s progress, though, and gently convince him to work with Seeed Studio or someone similar to get his version of Smart Tweezers onto maker’s workbenches the world over.

PIC LC Meter Improvements Add Li-Ion Battery And Charging Circuitry

September 20, 2011 by 7 Comments

[Trax] needed an LC meter and decided to use a tried-and-true design to build his own. The only problem was that he didn’t want to be tied to a bench supply or power outlet, which meant a bit of auxiliary design was in order. What he came up with is the battery-powered LC meter you see above.

The core of the original [Phil Rice] design remains the same, with slight modifications to drive a different model of character LCD. The code is mostly unchanged, but some calibration routines became necessary after [Marko] noticed bugs in the behavior after power cycling. Now the device will perform what amounts to a hardware reset about 700ms after powering on or changing between inductance and capacitance measuring functions. The project box is quite small, and to get everything to fit [Marko] sourced the Lithium Ion battery from a Bluetooth headset. He needs 5V for the LCD screen so he used a TPS61222 boost converter. To top off the battery he’s included a MAX1811 single-cell Li-ion charger, which has a couple of status LEDs visible through the case as seen above.

[Thanks Marko]

Using An Arduino To Measure Inductance

July 24, 2011 by 24 Comments

Measuring an inductor is not something that most multi-meters can do. You usually need a high precision resistor (1% or better) in series with the inductor, a function generator to put a signal through the circuit, and an oscilloscope to measure the result. But what can you do if you don’t have these tools on hand? [Andrew Moser] has a method that lets you pull it off with an Arduino and an LM339 quad comparator.

The circuit works by feeding a signal in from the Arduino. This waveform is affected by the LC circuit, filtered by the comparator chip, then read back out the other side by the Arduino. That resulting signal is a square wave, which is an easy target for the Arduino to measure. That timing measured from the square wave can then be used to calculate the inductor’s value.

This is quite handy if you’re winding your own inductors. Now you can precisely tune that Joule Thief you’ve been working on.

[via Dangerous Prototypes and Adafruit]

555 Inductance Meter

February 25, 2011 by 7 Comments

[Apexys] is performing some experiments with switched-mode power supplies and needed to compare the inductance of the coils he was using. His multimeter doesn’t have an inductance testing function, but he does have a 555 timer on hand. He put the 555 and some other parts together to create his own L meter. The writeup includes the theory behind this meter, with an incoming AC source converted to a voltage by an RC network.

Once he’d worked out the design it was time to build the circuit. Instead of printing a circuit board he created what he calls a DCB; Drawn Circuit Board. We’ve got to admit that this was way faster than using toner transfer or soldering point-to-point. We also like his use of an Erlenmeyer flask and a torch to heat the etchant. We don’t make PCBs in the winter because our Cupric Chloride is too cold to use outside but that may change now. The final piece in the puzzle is an analog meter which he pulled from an extra microamp meter he had on hand. Check out the demo after the break.

Continue reading “555 Inductance Meter” →

Theory Behind Evanescent Wave Coupling, Aka Wireless Power

January 14, 2011 by 30 Comments

[Alan Yates] is building a persistence of vision display and needs a way to transfer power from the stationary base to the spinning circuitry. He’s decided to go with wireless energy transfer and he’s sharing all of his research and experiment data from the development process. It comes in two forms, the written version we just linked to, and a 37 minute video which is embedded after the break. If you liked some of the inductive energy transmission devices we’ve featured in the past, [Alan’s] video will fill you in on the why’s and how’s by using a combination of illustrative schematic examples and measurements on test coils that he built.

Continue reading “Theory Behind Evanescent Wave Coupling, Aka Wireless Power” →

Floating Globe, Hacked To Rotate

August 31, 2010 by 56 Comments

they need to hire this guy

[Alexy Sha] has done this fantastic hack, where he modified a magnetic floating globe to be motorized and spin on a tilted axis. The original globe was simply levitating via a magnet mounted inside. Though you could spin it by hand, it wasn’t motorized, and actually floated completely vertically instead of being tilted.

[Alexy] wanted to take this idea further and make it automatically spin on a rotated axes. He built a rotation assembly that was basically a motor, hung off-center, attached at the center of the globe. He had to power it via a coil hidden in the base unit, so that it could remain light enough to float. He did a fantastic job and the final product seems like it is the true way it should have been sold.

Check out a video of it in action after the break. We actually like the spinning ring, when he’s testing it, just as much as the final spinning globe.

Continue reading “Floating Globe, Hacked To Rotate” →

Inductive Cellphone Charging Without Voiding Warranty

July 28, 2010 by 26 Comments

[Derek Hughes] wanted to use inductive charging on his cellphone without voiding the warranty. He picked up a Pixi charging backplate meant for a Palm Pre and scavenged the coil and regulator circuitry from it. To make the electrical connection with his HTC HD2 he removed the mini-USB plug from a charging cable and connected it with 30 gauge wire. The whole package will fit beneath the back plate for use with a Touchstone charger (as we’ve seen with the HTC Evo) but there was one problem. The metal backplate from the HD2 interferes with the inductive charging. For now he’s using tape to hold everything together while searching for a plastic case replacement.

He walks you through the hack in the video after the break. We’re usually not worried about voiding warranties, but a phone like this takes a lot of abuse and having warranty protection or even a service agreement isn’t a bad idea. Continue reading “Inductive Cellphone Charging Without Voiding Warranty” →