Monday, June 30, 2008

Identifying Electronic Components

How-to identify and locate information for electronics components you can recycle from discarded gadgets. Brandon gives us example pictures and descriptions for most types of electronics components to help you stock up your home electronics lab. This is a must read for new electronics hobbyist.

This article was submitted by Brandon Uhlig as part of the “Hobby parts for articles ” program. Brandon receives a Modern Device Company Bare Bones Arduino Kit for this fantastic article. Let Brandon know that you appreciate articles such as this by posting a comment. I hope to see many more articles like this one here at uC Hobby.

Scrounging for parts is a great way for hobbyists to save some money. You can get tons of parts out of discarded or unused electronics. But how do you identify all those parts? This article will give you some ideas on where to start.

The focus will be on common reusable through-hole components hobbyists will be most likely to scrounge and re-use.

Obviously, this is by no means a complete list, there are way to many different electronic components to put into a quick guide, but maybe this will give you some ideas to narrow down your search on an elusive component.


Resistors are one of the most used components in a circuit. Most are color coded, but some have their value in Ohms and their tolerance printed on them. To identify values, you can check out the Electronic Assistant software found in the Free Electronics Hobby Software article here on uC Hobby, or find one of the many online tools. A few of them can be found at in the Calculators section. A multimeter that can check resistance can also be helpful, providing the resistor is already removed from the board (measuring it while still soldered in can give inaccurate results, due to connections with the rest of the circuit). They are typically marked with an “R” on a circuit board.


Potentiometers are variable resistors. They normally have their value marked on them, normally marked with the maximum value in Ohms. Smaller trimpots may use a 3-digit code where the first 2 digits are significant, and the 3rd is the multiplier (basically the number of 0’s after the first 2 digits). For example, code 104 = 10 followed by four 0’s = 100000 Ohms = 100K Ohms. They may also have a letter code on them indicating the taper (which is how resistance changes in relation to how far the potentiometer is turned). They are typically marked with an “VR” on a circuit board.


Capacitors are also very commonly used. A lot have their values printed on them, some are marked with 3-digit codes, and a few are color coded. The same resources listed above for resistors can also help you identify capacitor values. They are typically marked with an “C” on a circuit board.


Inductors, also called coils, can be a bit harder to figure out their values. If they are color coded, the resources listed for resistors can help, otherwise a good meter that can measure inductance will be needed. They are typically marked with an “L” on a circuit board.

Crystals Oscillators

Crystals and Oscillators are also fairly easy to identify by sight. Most are clearly marked with their operating frequency printed on them. They are typically marked with an “X” or a “Y” on a circuit board.


Relays are typically enclosed in plastic, and many have their specs printed on them. They are typically marked with an “K” on a circuit board.


Transformers are normally pretty easy to identify by sight, and many have their specs printed on them. They are typically marked with an “T” on a circuit board.


Batteries are also pretty easy to identify, and are well marked with their specs.


Fuses can be easy to identify, and typically have their voltage and amperage rating marked on them.


Semiconductors, such as Diodes (typically marked with an “D” on a circuit board).


Transistors (typically marked with an “Q” on a circuit board),


Bridge Rectifiers (typically marked with an “BR” on a circuit board)


Integrated Circuits (typically marked with an “U” or “IC” on a circuit board), can take a little more work to figure out what they are. Many different types can use the same packaging, so they all can’t be identified by just their looks. In most cases the information you need is found in the device’s datasheet. The datasheet is a document containing the specs on the device and many will include example circuits, links to app notes, and other valuable information. They are typically in a .PDF format. If you have never used a PDF file before, you will need a PDF reader to open it. A couple of free ones can be found below. (Adobe Reader) (Foxit Reader)

To find a datasheet, you first need to find some info on the part. Luckily, they have part numbers which can be used to help identify them. They may also have the manufacturers logo on them. Finding the manufacturer can be extremely useful as the most up-to-date information is usually available on their website. For help in finding the manufacturer based on their logo, check out the following sites. They also include links to the manufacturer’s websites. Datasheets can normally be found under the support/download section, or you can put the part number in their search bar.

If you can’t find any information on the manufacturer, or are unable to find a datasheet on their website, you do have a few more options. There are several search engines on the web to help locate datasheets. Some free ones are listed below. You can search by part number, or even by a partial part number.

If those fail, you can try using a search engine such as google. Adding “pdf” to your search string can slim down the results, reducing the amount of sites just selling the part with no other useful information. There is also a chance of finding no information on a particular part. Some manufacturers will produce special order parts with “house” numbers, which can mean nothing except to the company that actually purchased them.

There are also many other components you may want to scrounge off a board, but may be difficult to find specific information on. They may not be marked, but you can find some good general information on the web to help you out.




And now for a little test :) See how many components you can identify on the following board. Answers can be found by scrolling below the board - No cheating!



1 Diodes
2 Piezo Buzzer
3 Transistor
4 Transformer
5 Relay
6 Inductors
7 Integrated Circuits (IC’s)
8 Capacitors
9 Crystal
10 Resistors

Nokia 3310 PCD8544 Based Graphical LCD Demo

Ah. Happy New Year!! This is one cool graphical LCD. Not only it is easy to programme, the Nokia 3310 LCD also consumes low power. I manage to get hold of one of this from a friend of mine who is no longer wanting his Nokia 3310 cellphone. =)
Therefore, I decided to dismantle the cellphone and see what I could do with its individual parts. And, what really interest me was the LCD screen.

The Nokia 3310 is based on a PCD8544 Controller which is manufactured by Philips. With this controller, you can easily interface any PICs to it via SPI.

A simple text demo. Also a New Year's greeting. :)

Its pinout is as follows:-
1 - VDD ==> Input voltage.
2 - SCK ==> Serial Clock.
3 - SDI ==> Serial Data Input.
4 - D/C ==> Data/Command Input.
5 - SCE ==> Chip Select.
6 - GND ==> Ground.
7 - VOUT ==> VLCD.
8 - RES ==> Reset.

There are quite a few source codes available out there on how to control the LCD with a PIC. One good instance can be found in Michel Bavin's website. His firmware was coded in CCS-C. He has done a great job by providing good explainations on the functions of his Nokia 3310 LCD codes. I do not have CCS-C, therefore I decided to translate some of his codes to Hi-Tech C and add alittle features to it. Both codes uses 'bit-banging' SPI. =)

There, the picture to the left is another snapshot of it. Here, I added a function to plot a smooth continuous line and its plot time is surprisingly rather fast. There's also the typical bar plot as shown below. The firmware provided here runs a demo program at main( ) to generate random numbers and plotting them on the LCD using both bar and continuously line plot. Simply adjust the delay in the programme to control the speed of the plot. It's cool to see animation, rather than a still picture. ;-)

Graphical animation of random number plots using both bar and continuous line plots.

Okay, I guess this should be it. Most of the explainations of the firmware are already provided in the C source file. Check it out. And as usual, here is the source code and the schematics. =)

Schematics : Nokia3310schem.jpg
Source codes :

PIC Development, Linux Style

In this article Steven Moughan shows us how to setup for PIC microcontroller development on Linux. Steve writes the following…

PICs are great, they really are… they have great features, decent instruction sets,
there’s lots to choose from, their manufacturer released a great IDE (MPlab) what could go wrong? Unfortunately the PIC is somewhat lacking when it comes to development software for Linux, and by this I mean IDEs and compilers. Here I will be dealing with getting your very own uC lab set up using Ubuntu Linux and some freely available tools.

By the end of this article we are going to have the following…

  1. An IDE to develop in (PIKlab).
  2. A C compiler to develop with (Hi-Tech C Lite)
  3. A PIC simulator and some utilities to help debugging (GPsim and GPutils)

This article was submitted by Steven Moughan as part of the “Hobby parts for articles” program.

Ok, so first you’re going to need something to write in… alright so gedit is good but it’s no IDE. The guys over at are doing a great job creating an IDE with similar functionality as MPlab, this is good no? Unfortunately for us (Ubuntu users) it’s developed for systems that run the KDE window manager (roll on Kubuntu). The first obstacle we are going to have to overcome is the lack of Qt libraries and KDE libraries in the base Ubuntu install. To do this we are going to make use of the Ubuntu repositories and the command line tool ‘apt-get’. Essentially the Ubuntu repositories store all the information for software that is available officially from Ubuntu and they also store the .deb files (don’t worry: you don’t have to know what they are), by using apt-get you can automatically install or remove software from your system with very little effort, to make this even better Ubuntu will let you know when there are updates available for whatever software you have installed on your system, as long as it’s done this way (or through Synaptic but that’s another beast altogether).

Installing Qt:

  1. In the command line interface (CLI) type in “sudo apt-get update” in order to update the available packages.
  2. Now that your list of repositories is up to date, you can type the following into the CLI:
    sudo apt-get install libqt3-mt

Installing KDE libraries:

  1. Use “sudo apt-get install kdelibs” to install the basic KDE libraries.
  2. Use “sudo apt-get install kdelibs4c2a” to install the core libraries & binaries for KDE.
  3. Use “sudo apt-get install kdelibs-data” to install the extra stuff for the kde libraries.

Ok, now your system should have the prerequisites for installing PIKlab, so its time to head on over to the PIKlab web site and get to downloading the latest package. We’re getting close now! Oh no! What do you mean there are no .deb packages?!? Fear not… a little command line utility called “alien” is here to save us! Depending on the options you chose when installing Ubuntu, alien may or may not be installed, if its not, yep, you guessed it, you can run “sudo apt-get install alien” and within a few seconds it will be here to rescue us.

What you need to do now is download the latest RPM package for PIKlab from their website. Now you can issue the command “alien ” and alien will generate the .deb file that we are going to cherish so fondly. Now the last thing we need to do to get PIKlab installed is issue the following command “sudo dpkg -i “.

Congratulations, take a break, the hard part is over now… We have a working IDE installed and ready. The bonus feature from this is that PIKlab will also work with the PicKit 1 and the PicKit 2 (although it does need some tweaking). In order to launch PIKlab now you can simply open a CLI and enter “piklab“.

Now that’s over, we can move on to installing HT Soft PIC C Lite. It’s free although a little restricted, and you will have to register to download it. Once you have the file downloaded, you’re going to fire up another CLI and navigate to where you downloaded the file and execute “chmod +x “, this will make the file executable, then the following command will begin the installation : “./“. After following the on-screen instructions you should now have HT Soft PIC C Lite installed.

Ok, now we have an IDE and a compiler… What else do we need? How about something that will help us debug our code? We’re going to install the GPsim and GPutils tools—these are great tools. GPsim is the “GNU PIC Simulator” and GPutils are the “GNU PIC utilities”. They are very useful, especially GPsim as it has loads of add-on modules such as HD44780 controllers and the like. So now that you know what it is we can go get it installed on our system.

Again “apt-get” is going to be our savior. First we’re going to install GPsim, to do this we use “sudo apt-get install gpsim“. Next we’re going to do GPutils… you get the idea of this apt-get thing yet? I’m going to leave this one to you.

Ok, now we have our IDE, compiler and simulator set up, the rest is up to you…

Thanks for reading!

Convert a computer power supply to lab power supply

Things You'll Need

An obsolete computer with an ATX 250W, 300W or 400W power supply.
Wire cutters, needle nose pliers, drill, reamer, soldering wire, soldering iron, electrical tape, heat shrink tubing
Binding posts for output terminals,
LED, current limiting resistor for the LED, power resistor to load the power supply, a low wattage switch.


Unplug the power cord from the back of the computer. "Harvest" a power supply from a computer by opening up the case of the computer, locating the gray box that is the power supply unit, tracing the wires from the power supply to the boards and devices and disconnecting all the cables by unplugging them.

Remove the screws (typically 4) that attach the power supply to the computer case and remove the power supply.

Cut off the connectors (leave a few inches of wire on the connectors so that you can use them later on for other projects).

Discharge the power supply by stripping the insulation of the ends of a black and a red wire and connecting them together for a few seconds.

Gather the parts you need: binding posts (terminals), a LED with a current-limiting resistor, a switch (optional), a power resistor (10 ohm, 10W or greater wattage, see Tips), and heat shrink tubing.

Authored by Abizarl at WikiHow, Added: 30 May 2007

4 Tips to Extend Your Lithium Battery Life

1. Battery Memory - When I first got my new cellphone, my friend recommended to fully drain the battery before recharging it. His reasoning was connected to the idea of battery memory. Allowing the battery to fully discharge then recharging to max, supposedly gives you the complete battery capacity. Otherwise, if you simply charged from the half way point to max battery capacity, the battery would treat the half way point as the empty point, thus cutting your battery capacity in half.

Problem is battery memory doesn’t apply to Lithium batteries, this advice was meant for Nickel based batteries. Fully discharging your Lithium battery frequently can actually be quite harmful to your battery’s health, possibly rendering it completely unusable if energy levels go too low.

The good news is today’s lithium batteries have a safety circuit in place to insure the battery doesn’t reach the point of no return. The safety circuit isn’t fool proof of course, if you leave your battery completely drained for a few days, even the circuit’s protective measures won’t save it.

2. Battery Calibrating - There is some benefits to fully discharging your lithium battery periodically, for laptops especially this can be important. If you start to notice your battery meter is becoming more and more inaccurate, it may be time for some battery calibration. By allowing your lithium battery to fully drain, this will help the battery recalibrate allowing for more accurate measurements of battery life. This should be done once every 30 charges or when you notice battery readings are off.

Authored by Iron Cook at Spicy Gadget Roll, Added: 20 Jul 2007

Motherboard PCB Bracelet

This bracelet is for the geeks of the leet'est and also for looking funky. You will need 1 Computer
motherboard and some telephone wire and thick copper wire (size of the earth wire for house wiring)

It is easier to cut up all the pieces you need and refining them then do all the easier things later.

You will need a dust mask when cutting up and filing the motherboard pieces, although it most likely won't kill you breathing in the PCB dust it will not do any good and could possibly destroy your lungs. I didn't wear a dust mask but my excuse is that there wasn't any available, it doesn't smell nice and can get quite nauseating.

The easiest way for cutting the mo-bo. is to cut strips of the width that you want for your bracelet, so cutting strips down the mo-bo. of your choicest electrical components, and then cut the strip up into segments. On after thoughts I would make the segments a little longer so you don't need as many for the circumference around the wrist.

Also salvage the bigger chips because they can become segments and will add geek points to it.

After you have cut the pieces washing them in water will remove most of the dust off them, don't worry, water won't affect them.

Authored by llama13 at Instructables, Added: 1 Jul 2007

Nokia 1110 mono to color display MOD

Florin shows us how to convert a Nokia 1110 cell phone’s normal monochrome LCD to a color LCD scrounged from a Nokia 1600. This article does not have much to do with microcontrollersMaker spirit. or electronics hobby work but it is interesting and shows that you can hack your cell phones to make them suit your taste. This is very much in the

The idea for the project came when I wanted to change the Display LEDs from my Nokia 1110. The original LEDs are green, so you get a green light behind the screen, well I didn’t like that so the main goal was to place some white LEDs to get a white background. But luckily I stumbled on a problem that made me reconsider the mod.

The LEDs for the display on all modern phones are built-in inside the LCD so there are 2 pieces of very thin glass and the LEDs are placed between them. No possible way for me to change those.

Now if think about it, it is probably a bad idea to place white LEDs behind the original LCD, because the contrast will be considerably lowered. The point is I ended up changing the whole display.

If you want to do this mod yourself, you’re going to need only one tool, and that’s a special screwdriver. I don’t have a code, or a name for it but it just fits on Nokia screws. I paid about $5 for one. Besides the tool you’re also going to need a broken Nokia 1600, just to use the color display from it.

I had a broken Nokia 1600 lying around, so I used the display from it because the connector is the same as for the monochrome display from Nokia 1110. Probably there are other displays from Nokia that have the same connector and will work on Nokia 1110, so if you have a Nokia in the 1xxx series you should check to see what kind of display and connector it has.

The first step is to disassemble the Nokia 1110, and you start by removing the battery and the battery cover, next you remove the front cover together with the rubber keyboard

Nokia 1110 Mod_removing covers

Now you should be able to see the screws that keep everything together. Grab that special screwdriver and start removing the screws one by one. The different parts are layered, so remember their place so you can put them back together.

Nokia 1110 Mod_removing screws

After removing all screws the first thing that comes off is the black frame that holds the LCD in place and also houses the speaker.

Nokia 1110 Mod_removing LCD frame

Now you should be able to see the LCD connector, you simply disconnect it.

Nokia 1110 Mod_LCD connector

Now leave the Nokia 1110 as it is and start disassembling the Nokia 1600 to take its display out. Mine was already missing the screws so it was easy. Here is the color LCD and its connector; you can notice it’s the same as for the monochrome display.

Nokia 1110 Mod_ Color LCD connector

The displays have the same size and shape, so now just place the color LCD inside the Nokia 1110 and connect it to the main board.

Now all you have to do is re-assemble the Nokia 1110, just place the parts as they were and insert the screws.

Nokia 1110 Mod_ placing covers back

If you made it so far and everything went okay, power on your phone and it should look like mine. It’s cool to have a color display on a phone that everybody thinks its monochrome. I haven’t researched the idea behind this compatibility, but I can only imagine that Nokia builds the same main board for several phones, in order to reduce the costs. It’s cheaper to run one manufacturing line instead of two.

Nokia 1110 Mod_the new colored display_1Nokia 1110 Mod_the new colored display_2Nokia 1110 Mod_the new colored display_3Nokia 1110 Mod_the new colored display_4

Aerosmith gets unboxed

Guitar Hero: Aerosmith gets unboxed, rag-covered mic stand not found

Well, what do you know? That Guitar Hero axe that was spotted a few months back on How I Met Your Mother was actually a sneak peek of the six string that comes bundled with the new Activision title. The unwavering rockers over at FW Labs were able to secure a copy of the game in Chile before most everyone else on the planet, and rather than enjoying their fortune without telling a soul, they decided to snap a host of photos and even upload a few videos of the experience. The new toys in the attic are right there in the read link.

GLaDOS GPS voice pack

An enterprising nerd by the name of Ryan VanMiddlesworth is clearly a bigger

Portal fan than you, since he's cobbled together a GLaDOS-simulating voice pack for Garmin Nüvis. Just don't try to prevent "GLaGPS" from constantly trying to divert you to cake-related points of interest, else you may find yourself tossing your Garmin into an incinerator. Video after the break.

An enterprising nerd and Portal fan by the name of Ryan VanMiddlesworth has cobbled together an installable GLaDOS-simulating voice pack for Garmin Nüvis. Having "GLaGPS" guide you to point B seems like it'd be only slightly unnerving, but that's mostly to do with the

fact that its constantly trying to divert you to cake-related points of interest. Video after the break.

Powerful 7.1 AV Amplifier - TX-SA706

TX-SA706: A Powerful 7.1 AV Amplifier from Onkyo

Onkyo released a new 7.1 AV amplifier equipped with an HDMI1.3 port, the TX-SA706X. Our new amplifier features five HDMI inputs and one HDMI output supporting 1080p video signals. It can reproduce the latest audio codec such as Dolby True HD, DTS-HD Master Audio…

The TX-SA706X also provides a maximum output of 200wx7, a frequency response of 5Hz-100,000Hz (Not sure if this is useful…), and includes Audyssey Dynamic EQ Processing.

It should be available July 19th for 1,120ˆ

IM-R300 - New Touch Phone from Pantech

IM-R300, a New Touch Phone from Pantech

Here's a new phone made for the Korean market, the IM-R300. Under it sleek design it carries some nifty features like a DMB TV tuner, GPS, a 2Mpix Camera, MP3 player, 260Mb of internal Memory, microSD, a 2.6” LCD with a WQVGA screen (400x240), HSDPA, WCDMA, GSM, eWallet functions and payment. With a total weight of 111g and a size of 51x102x13.9mm.

So far only Available on Korea's SKY network. Pretty girl, unfortunately not included...

Mitsubishi's new iSP 149 series

Mitsubishi's new iSP 149 series LCDs have it all in one place

If you're a lazy ass consumer (the very best kind), bent on pulling a device out of the box, plugging it into a wall, and never messing with another bit of "setup" again, you're certainly not alone. In fact, most folks never lift a finger to calibrate their displays, plug better speakers in, or place those speakers in actually advantageous spots. To that end, Mitsubishi is debuting its new LT-46149 and LT-52149 LCDs with integrated 16-speaker sound projectors. Similar to the sound bars offered up by many home audio manufacturers, the "Integrated Sound Projector" (iSP) is designed to bounce sound off walls and around the room to give the illusion of surround sound. The perk of TV integration is an easy to use room configuration on-screen tool to specify your room's dimensions, couch placement and preferred sweet spot size. At the end of the day, your sound is all coming from one spot, so directionality isn't going to quite match a for-realsie surround sound setup, and the system we listened to was a little sharp in the high end, but it's certainly a unique and appealing offering from Mitsu to the everyman TV watcher. The TV itself is CableCard ready, can support sound over HDMI and PCM inputs, and offers Mitsu's 120Hz film dejuddering -- that rather awkwardly makes your favorite films look like they were shot by a TV news crew. The 46-inch and 52-inch LCDs will sell for $3,299 and $3,699, respectively.

Sunday, June 29, 2008


When this electronc project first appeared in the American magazine ELECTRONICS NOW back in July 1998 I was somewhat initially amazed by the claims made for its performance.
completed lc meter kit
As it subsequently happened some months later, I had an opportunity to purchase a complete kit for myself from Neil when a member of my family visited the U.S.A.

I found the instructions quite easy to follow and yet although I am an experienced constructor, albeit suffering from diminished eyesight, I found that even I could easily have this kit up and running as was claimed within a couple of hours. Although I must mention I did take time out for several cups of coffee.

I found all the claims made about the project and the kit were perfectly true. If you really want a first class piece of test equipment to measure inductance or capacitance then this project is really for you.

Neil is quite happy for anyone to build it themselves using their own source of parts but really why would you bother when you can obtain the pcb and everything else so conveniently at one place and directly from the author himself?

Currently this very handy electronic project comes in complete kit form for the economical price of $US 99.95 + s/h.

If you're not especially confident of your construction skills or you simply don't have the time, then Neil will supply a ready built and tested unit for only $US129.95 + s/h. Commercially made units cost a great many more times than that amount.

On behalf of all, I would personally like to thank Neil for sharing his LC Meter project with us, I think he has been most generous. Also I think you will find the underlying principle of Neil's design to be rather ingenious, I most certainly did. May Neil continue to enjoy the success that he so richly deserves.

Read on and enjoy this unique project as much as I did myself.

Disclaimer - apart from being a satisfied user I have no commercial relationship whatsoever with Almost All Digital Electronics (AADE) and I have paid the full advertised price for my LC Meter kit.

Any advertising benefit which might be derived by AADE on this page is by way of compensation for presenting an interesting electronic project for our mutual benefit and enjoyment. The links to AADE are provided to assist my readers.

.001 mH (1 nH) to 100 mH (most units measure to 150 mH)
.010 pF to 1 mFd (most units measure to 1.5 uF)
(capacitors must be non-polarized)

1% of reading Typical
    Typical means the average error of 83 different components compared to an
    · HP4275A digital L/C meter (test frequency 1MHz) for components ranging from .1uH to 1mH and 2.7pf to .068uF,
    · B&K 878 digital LCR meter (test frequency 1KHz) for components ranging from 1mH to 100mH and .1uF to 1.6uF.


16 Char intelligent LCD
Four Digit Resolution
Direct display in engineering units, ie: Lx= 1.234 mH / Cx= 123.4 pF

Sampling Rate:
Approximately 5 samples / second. (will track while adjusting adjustable components)

The unit displays values in one of two modes which can be changed during operation. The "micro mode" displays values in uH, mH, pF, and uF when applicable. In this mode, for example, 10.00 nano-Farads displays as .01000 micro-Farads and 1 nano-Henry displays as .001 micro-H. It is for old timers like me and is the way many parts are marked. The "nano mode" is for those more metrically inclined. Table 1 shows how each range is displayed in each mode.

nano mode
micro mode
nano mode
micro mode
000-999 nH
0.000 - 0.999 uH
0.00 - 0.99 pF
0.00 - 0.99 pF
1.000 - 9.999 uH
1.000 - 9.999 uH
1.00 - 9.99 pF
1.00 - 9.99 pF
10.00 - 99.99 uH
10.00 - 99.99 uH
10.00 - 99.99 pF
10.00 - 99.99 pF
100.0 - 999.9 uH
100.0 - 999.9 uH
100.0 - 999.9 pF
100.0 - 999.9 pF
1.000 - 1.999 mH
1.000 - 1.999 mH
1.000 - 9.999 nF
1000 - 9999 pF
10.00 - 99.99mH
10.00 - 99.99mH
10.00 - 99.99 nF
.01000 - .09999 mF
100.0 - 999.9 mH *
100.0 - 999.9 mH *
100.0 - 999.9 nF
.1000 - .9999 mF

1.000 - 9.999 uF *
1.000 - 9.999 uF *

TABLE 1. Display Options (* Some values out of range)

One input pin to the micro controller is a jumper which determines if the unit powers up in the "micro mode" (jumper open) or "nano mode" (jumper shorted).

Operating Modes

When the Lx and Cx switches are off pressing the ZERO button sequences L/C Meter IIB through five different operating modes.

    READY MEASURE n measures Lx or Cx and displays the result in "nano mode" ie: Lx = 99 nH, Cx = 12.34 nF

    READY MEASURE u measures Lx or Cx and displays the result in "micro mode"
    id: Lx = .099 uH, Cx = .01234 uF

    READY MATCHnMODE first measures a reference component Lz or Cz and displays the value in "nano mode". When the ZERO button is pressed this value is stored in RAM and the difference between it and subsequent components is displayed in "nano mode"
    ie: Lx - Lz = 99 nH, Cx - Cz = 12.34 nF

    READY MATCHuMODE first measures a reference component Lz or Cz and displays the value in "micro mode". When the ZERO button is pressed this value is stored in RAM and the difference between it and subsequent components is displayed in "micro mode"
    ie: Lx - Lz = .099 uH, Cx - Cz = .01234 uF

    READY MATCH%MODE first measures a reference component Lz or Cz and displays the value in "nano mode". When the ZERO button is pressed this value is stored in RAM and the ratio of the difference between it and subsequent components is displayed in percent.
    ie: (Lx - Lz)/Lz*100 =12.34%, (Cx - Cz)/Cz*100 = 12.34%

Note that a positive reading in the matching modes means Lx is greater than Lz or Cx is greater than Cz and visa versa.

L/C Meter II is intended to measure inductors and capacitors "out of the circuit". Inductors must have a reasonable Q for their value and negligible distributed capacitance for their value. I have tested it using commercially available RF chokes ranging from 0.1 micro-Henry to 1000 mico-Henry , Hash chokes up to 100 mico-Henry wound on ferrite rods, on Pi-wound RF chokes up to 7.5 milli-Henry, on toroid wound inductors up to 150 milli-Henry (such as the HI-Q series obtainable from Mouser Electronics), and on several slug tuned inductors from a Coilcraft Slot-10 designers kit (similar to the TOKO line of tunable inductors).

Circuit Description

The Oscillator

The key to L/C Meter IIB's operation is the oscillator circuit of FIGURE 1. The LM311 is a voltage comparator. When power is applied, the voltage at pin 2 is 2.5 volts causing the output to be at a level of 5 volts. This charges capacitor C4 through resistor R4 until the voltage at pin 3 equals 2.5 volts. As it reaches 2.5 volts the output switches to a low level inducing a transient into the tank circuit composed of L1 and C1. The transient causes the turned circuit to ring at it's resonant frequency. The ringing causes a square wave at the resonant frequency to appear at the output of the voltage comparitor. The square wave is coupled back to the tuned circuit through R3 and C3 sustaining oscillation.

For the nominal values of L1 (68 uH) and C1 (680 pF) an increase in L of 1 nH (.001 uH) or an increase in C of .01 pF produces a frequency change of slightly more than 5 Hz. A 0.2 second measuring period can resolve 5 Hz and therefore .001 uH or .01 pF.

Besides being simple, this oscillator circuit is very reliable in that it always starts and can tolerate a large variation in the inductance and capacitance used in the tank circuit.

The Micro-computer

The complete schematic is shown in FIGURE 2. The output of the oscillator is applied to the RTCC, Real Time Clock Counter, pin. This increments an 8 bit counter inside the micro-computer. The micro-computer accumulates the count for a period of 0.4 seconds. The frequency is then the accumulated count divided by the period. Discrete signals from the Lx, Cx and ZERO switches are input to the micro-computer so it knows what the operator wishes it to do.


During the calibrate cycle the micro-computer first measures F1, the frequency when only L1 and C1 are in the tank circuit. The frequency will be:

In order to obtain another equation, so that we can solve for both L1 and C1, a known capacitor is switched into the tank circuit. The micro-computer energizes relay RLY1 by raising the CALIB line to a logic high level which switches capacitor C2 into the tank circuit. C2 is a 0.5% tolerance 1020 pF capacitor composed of C2a and C2b. C2a is a 1000pf 2% polystyrene capacitor. C2b is an NPO ceramic which in parallel with C2a is 1020pf +/-5pf. This causes the frequency to become:

The two equations can be solved simultaneously to give:

and finally:

Because of this self-calibration capability, the exact values of L1 and C1 are not critical and 10% tolerance components are used. The accuracy of the device is dependent upon C2 which is a .5% tolerance capacitor combination.

Measuring Inductance and Capacitance

When the Lx and Cx switches are off the micro-computer continuously measures F1 to track any drift in frequency. When the Lx switch is depressed the unknown inductor is placed in series with L1. The total inductance is then L1 + Lx. This causes the frequency to change to:

This equation can be solved, simultaneously with the equation for F1:

to produce:

Similarly when the Cx switch is depressed the unknown capacitor is placed in parallel with C1. The total capacitance is then C1 + Cx.

Which is solved for Cx, with the equation for F1, to produce:

Stray Inductance and Capacitance

The circuit traces on the PCB, the switches , and the test leads all contribute a small amount of "Stray" inductance (Ls) and capacitance (Cs). These stray values add to the values of Lx or Cx. The unit is zeroed by pressing the ZERO switch which causes the unit to store the values of stray inductance or capacitance and subtracts them from the measured values. The values displayed are thus:


To zero Ls the operator must short circuit the test leads, press Lx and then press the ZERO button. Similarly, for capacitors, the operator open circuits the test leads, presses Cx and then presses ZERO.

The stored values of Ls and Cs are saved until the operating mode is changed. When measuring components, it is not necessary to re-ZERO between components. When the operating mode is changed from MEASURE to MATCH these values are reset to zero.

You will notice from the above equations that inserting an unknown always causes F2 to be less than F1. If an inductor is inserted when the Cx switch is depressed the result will be an increase in frequency, F2 greater than F1, rather than a decrease. This is because the inductor has been placed in parallel with L1 and inductors in parallel always are less than the value of the smallest of the two values. If the unit detects an increase in frequency it will display "NOT A CAPACITOR". This does not work for very large values of Lx. The decrease in the effective value of L1 is trivial while the shunt capacitance of the large inductor is significant and the frequency will decrease causing an erroneous reading. The effect of putting a capacitor in when the Lx switch is pressed is similar except the oscillator tends to stop causing F2 to be zero. The unit detects this and displays "NOT AN INDUCTOR". This is not true for very large values of Cx in which case the unit may display an erroneous reading.

L/C Meter IIB can zero out ANY value in it's range. If a value is inserted and ZERO'd the unit will display the difference between it and subsequent components similar to the MATCHnMODE and MATCHuMODEs. The difference in the MATCHxMODEs is that the range is frozen to the resolution of the initial component. This limits the minimum difference in values to be 1 part in 10,000 or .01%. The reason for this may not be obvious. The maximum resolution of the unit is four digits at the value of the components being measured. Consider two components, one with an exact value of 5000 pF and the other with an exact value of 5010.25 pF. The difference would be 10.25 pF, however the unit cannot resolve less than 1 pF at this range and it would be misleading to display the fractional portion of the difference.


The unit is indeed simple and there is no particular order of assembly. Refer to parts layout, for important information.

NOTE: there is only 3/8 inch (10 mm) space under the display, leave enough lead length to tip taller parts at an angle so that the vertical dimension does not exceed 3/8 inch (10 mm).

Precision alignment of the switch pins is required for easy installation. Align the pins parallel to each other by eye-ball (particularly the two rows of pins when viewed from the rear of the switch). Start by inserting one or two rows of pins with the switch at an angle to the PCB. Turn the assembly upside-down with the switch resting on top of your bench and press down on the PCB. Do no press down on the switches as there is a risk of pushing the pins all the way out of the body of the switch.

Solder J1, the female square post header, at the top of the PCB. Solder just one pin then make sure the connector is perpendicular to the PCB then solder the rest.

Install the contrast control, R6, on the back of the PCB otherwise you will not be able to adjust it with the display installed. Install the two 3/4 inch (20 mm) spacers for the test jacks as shown in Mechanical Detail. This should complete the PCB assembly.

Decide which type of capacitor display you prefer the unit to be in upon power-up. If you prefer the nF method solder a jumper wire as indicated on the parts layout.

Pass the leads from the battery clip through one of the slots in the battery box of the case and solder them to the appropriate pads of the PCB. Plug in the display, turn the contrast control fully clockwise and turn on the unit. The unit will display "WAIT" for 10 seconds followed by "CALIBRATING" for two seconds followed by "READY MEASURE x". If so, your up and running. Adjust the contrast control so the background is just barely visible. Install the PCB in the bottom of the case using three #4 sheet metal screws. Install the top cover of the case and install the binding posts as shown in Figure 4, Mechanical Detail. Test leads should not exceed 4 inches (100 mm) in length with a banana plug at one end and alligator clip at the other.

It may be necessary to "move" the edge of a hole or slot in the case. This is easily done using sandpaper, file or hobby knife. Before fitting the test jacks or screws in the back of the case, fit the cover and squeeze the case together while testing the switches for binding to the edge of the slot. "Move" the edge as required.


It is very unlikely you will have any problems, however, if you just can't seem to get it to work I will try to fix it free except for a $US4.00 return postage and handling fee.

If it did not work, remove the PCB and carefully inspect to see you have soldered everything that should be soldered and have not soldered anything that should not be (look for solder bridges). Bad soldering accounts for 99% of units failing to work immediately. Here are some hints on where to look.

1) Blank display, contrast control not adjusted correctly. Start with it fully clockwise.

2) Blank display, check 5V power to CPU and display.

3) Displays 8 black squares, CPU not communicating with display. Check solder around CPU and display. CPU crystal not oscillating. Check with oscilloscope if possible.

4) Displays WAIT, then CALIBRATING and sticks in CALIBRATING. A) Oscillator (LM311) is not oscillating. Check soldering around LM311, LM311 properly installed, parts properly installed. C3 in backwards?. B) ZERO button stuck in or not soldered. Check continuity to ground from pin 13 of the CPU.

5) Seems to work but readings appear way off from components marked value. Calibration capacitor not correctly installed or relay in backwards. (relay should be installed with it's part number opposite the switches (facing the LM311) and little circle toward top of PCB).


The typical stray inductance is .04 to .06 m H's and the typical stray capacitance is 5 to 7 pF's. When measuring inductors less than 5 m H's or capacitance's less than 50 pF's it is advisable to ZERO the unit first. For larger values the strays are insignificant to the result. It is difficult to retain a reading of 0.000 pF's because of the extreme sensitivity of the unit. Your body capacitance influences the reading. Try ZEROing the capacitance and then move your hands around the test leads without touching them. You will find your can adjust the reading a few hundredths of a pF.

To measure inductance place the unknown across the test leads and depress Lx. To measure capacitance place the unknown across the test leads and press Cx.

The oscillator tends to drift a few Hertz during the first few minutes of operation. When measuring very small values the unit should be allowed to warm up for about five minutes. With a resolution of 5 Hz, thermal drift will always occur as evidenced by a slowly drifting reading. The first readings after pressing Lx or Cx are the most accurate.

Accuracy and Resolution

L/C Meter IIB is specified at 1% of reading. I have about 60 components which I had measured on a HP4275A L/C meter. Measuring these components on L/C Meter IIB found an average error of 0.23% for inductors and 0.24% for capacitors. These values ranged from .1 mH to 6.8 mH and 2.7pF to .068 mF. These measurement were for a single unit and could vary, from unit to unit, by .5% as a function of the exact value of C2.

L/C Meter IIB has four digit resolution which for small values of L and C are 1 nH and .01 pF. You cannot accurately measure values this small. The resolution greatly exceeds the accuracy. You can measure values as small as .01 mH and .1 pF with about 15% accuracy. You generally won't find components this small. For example a piece of wire less than one inch long is .01 m H. The resolution is, however, relative and can be used for sorting a batch of similar components as it truly does indicate which are slightly larger of smaller than others. Also, for small values of inductance, the leads will contribute quite a bit to the value. Measuring from the ends of the leads instead of next to the body of the component can add up to .025 mH.

For small values the frequency of operation (test frequency) is about 750 KHz decreasing to about 60 KHz at .1 m F's or 10 mH's and about 20 KHz at 1 m F or 100 mH's.

Parts List
R1, R2, R3 100K ohm 1/4 watt
R4 47K ohm 1/4 watt
R5 1000 ohm 1/4 watt
R6 10K ohm potentiometer
C1 680pF (disc ceramic marked 681 500v)
C2a 1000pf 2% (C2a and b are packed in a little brown envelope)
C2b 5, 10, 15, 20, 24, 27, 33, or 39pf NPO

as required to make 1020pf total.

C5,C6 .1 m F ceramic (tan monolythic marked 104)
C3 10 m F /10v Tantalum (tan tear drop shaped, observe polarity)
C4,C9,C10 10 m F /10v electrolytic (black radial, observe polarity)
C7,C8 22 pf ceramic (brown disc marked 22J)
X1 8.0 MHz crystal
L1 68 m H (blue)
U1 LM311N voltage comparitor
U2 PIC16C622 microcomputer
U3 78L05 voltage regulator
RLY1 SPST N.O. reed relay (has diode, observe install orientation)
DISP LM-16151 or equiv'
J1 14 pin square post socket (built onto the display module)
P1 14 pin square post plug (install on PCB)
Lx, Cx, PWR DPDT alternate action SW
ZERO DPDT momentary SW
Test Jacks 5 way binding posts
Schematic Diagram