Solder, not Sodder? The Story behind the Silent (or not so Silent) L

|ˈsɒldə(r)| and |ˈsəʊdə(r)|

The word solder originates in Middle English. The Latin origin is the word solidaire, meaning to “to make solid,” which is where the -l- in solder comes from.

Solidaire (v.) – to join, be united, standing together, or interdependent.

The word more immediately comes from the Anglo-French word soudure. This Anglo French word is similar to the contemporary French verb souder. The word eventually evolved in English to its current spelling.

The modern form of the word solder in English is a re-Latinization from the early 15th century. The -l- was dropped on the way to Old French, which was common (for example, pulverem to poudre, collum to cou, calidus to chaud, etc.). Note that the -l- in solder is typically sounded in British English.

Interestingly enough, the English translation of the French word soudure refers to welding, not soldering. The word for soldering in French, soudage, is similar and shares a common root.

Souder [soo-deh] (v.) – to solder or to weld.

Avec le fil a souder, which literally means with the line of solder, applies to soldering whereas soudre a l’arc refers to arc welding. Isn’t everything a little more elegant in Latin languages? This is yet another example of a simple yet beautiful group of shared words. Why have two distinct words, weld and solder, for processes that are so similar? Almost as logical as the Standard system of measurement where lbs refers to pounds and oz refers to ounces.

Anyhow, next time you are wondering why there is a silent -l- in solder — or not silent if you live in England — you can recall this bit of knowledge and clue in your EE classmates […who will turn to you and say, “Hey, Chomsky, the Linguistics building is thataway” – Ed.].

Constructing a DIY 3D Printer

Many of our customers are hobbyists who use our components as part of their maker or DIY projects and we’ve worked with a number of customers shopping for stepper motors and other motion control supplies for building a 3D printer. It occurred to us that a great way to gain insight into our customers’ needs and challenges would be by building a 3D printer ourselves!

We began by comparing and evaluating various models on RepRap, which is a Wikipedia of sorts for open source 3D printers. There are many models of DIY printers with many iterations of each model, but we finally settled on the Mendel90, which is a slight modification of the Prusa Mendel. We liked the clean look and versatility of the printer, so we ordered a kit from the printer’s creator, Nophead. The kit didn’t include a power supply, so we used our 600W 12V power supply.

Here is an overview of the build in pictures:


The unpacked kit, ready for assembly

The unpacked kit, ready for assembly


Frame assembly

The assembled printer dibond



The threaded rod, rod guide, and x and z motors after being assembled and mounted


The Melzi controlled board after mounting (since our power supply has an integrated fan, the two resistors on the right were unnecessary)


Assembled 3D printer

The completed printer assembly with the filament from the kit on the spool (we used our 3mm glow-in-the-dark ABS 3D printer filament from MG Chemicals for the subsequent print)


It took us about a week, working a few hours time, to build the 3D printer and it certainly isn’t a simple process. Don’t expect to breeze through a project like this. Although there are many components and sub-components, with the proper tools and enough determination most people can build one of the 3D printers on RepRap.

3D printed elephant

Our print of an elephant by LeFabShop we found on Thingiverse, an excellent resource that has thousands of .stl files to print (you may have noticed we put polymide tape on the glass surface, which we found helps with the removal of the plastic parts and adhesion of filament)


The post-assembly process was equally challenging. It takes a bit of time to get familiar with the software used to convert a generic sketch .stl file to .gcode that the printer can understand.


Logo screenshot

Here is a sketch of the Circuit Specialists logo from Google SketchUp that we converted to .gcode for printing


Printed logo

…and here’s the logo after printing


As previously mentioned there are dozens of models of DIY 3D printers for you to choose from. That being said, most builds use many of the same parts, so we put together a bill of materials (BOM) for building a 3D printer. We hope you find it useful!

And, finally, here is a time lapse we filmed during one of our elephant prints.

Common Parts & Tools List for DIY 3D Printers

(Note: This is not a complete BOM that applies to all 3D printers.)

600W 12V power supply

Polymide tape

NEMA 17 motors

3mm PLA/ABS 3D printer filament

Jumper wires

Lithium grease

Multimeter (qualifies as free gift on orders over $50)


Soldering station

Plier & cutter set

Cutter/Stripper 20-30 AWG

Heat shrink wrap


Surface cleaner

Axial fan (if using non-cooled power supply)

Wire Gauge Guide

Roll of 22 AWG wire

Selecting the appropriate gauge of wire for your next electrical project will ensure that the circuit functions properly and safely. Wires come in a variety of thicknesses, most often measured as a gauge number. American wire gauge (AWG) is a standardized wire gauge system for wire diameter, and the cross-sectional area of each gauge is important for determining its capacity to carry current.

Use the following formula to calculate the diameter of wire between No.  0 and 36 AWG  (where n = gauge number):

d_n = 0.005 inch x 93 ^ ( 36 - n / 39 ) = 0.127 mm x 92 ^ ( 36 - n / 39 )

Please note that as the gauge number increases, the diameter of the wire decreases. Because of this inverse relationship, selecting the right wire gauge can be quite confusing. When we use No. 18 AWG wire in the equation above we see that the diameter of the wire is .0403″ (1.024mm), and when we solve this equation for No. 22 AWG wire we find that the diameter is 0.0253″ (0.644mm). Notice that the No. 22 AWG wire is thinner than the No. 18 AWG wire.

As electricity flows through wires they tend to heat up depending on how much power (usually measured in watts or kilowatts) flows through them as well as the length of the run. The longer the run, the greater the voltage drop through the wire. To compensate for this voltage drop, sometimes you may need to select a thicker wire. No. 18 AWG wire is generally accepted to carry a maximum of 10A, whereas No. 22 AWG wire is accepted to carry a maximum of 5A.

Again, when determining which diameter of wire is appropriate you must consider the length of the run and how easily the wire will be able to dissipate heat. If your wire cannot quickly dissipate heat the insulation may melt, so when in doubt always err on the safe side.

Tech Tip: Measuring Energy Requirements for Home Appliances

As energy costs continue to rise and as alternative power systems like solar energy become more cost effective, it is important to know how much energy your electrical appliances are using. Since residential and commercial facilities use AC power, the AC voltage and power values must be converted to the equivalent DC values required by electronic instrumentation. This article will explore one way to convert the AC quantities into DC values suitable for measurement by modern electronic circuitry.

There are several methods you can use to convert current to voltage including using a shunt resistor or a current transformer. The AC voltage produced must be converted to DC values. You will not be able to use a simple rectifier circuit due to the low level signal produced by the shunt or transformer and therefore you will need an active circuit that will eliminate the forward voltage drop produced in a simple rectifier arrangement. This will allow you to measure very small AC current values with a small value shunt or standard current transformer.

The simple full-wave active rectifier circuit shown below is only an example circuit and is by no means the only possible implementation. This circuit uses readily available components and is easy to build on a simple prototyping printed circuit board. This circuit should produce a DC output voltage that is proportional to the AC current value being drawn by the electrical appliance whose energy consumption you’re measuring. If you need a different scale factor you may use the unused op-amp in the LM324 quad op-amp to provide additional gain or scaling.

Because electrical power is what we’re interested in, we should also measure the AC voltage powering the appliance. But for a first order approximation we can simply substitute in the known AC voltage of the household wiring, since this value does not change appreciably and is normally maintained at a constant level by the power company at a nominal 120 volts. We can use the Ohm’s law power formula P = V x I (Power = Voltage x Current) to determine the power dissipated by the appliance.

P = V x I = Voltage x Current = Watts

This application note has shown a simple method you can employ to obtain a reasonably accurate indication of the energy consumption of a standard household electrical appliance. The resulting voltage can be suitably scaled and displayed on a digital panel meter or used in any data acquisition system. The circuit diagram for the active rectifier circuit is shown below.

Click to enlarge

What Can You Do with the Aardvark HD3M Inspection Camera?

One of our satisfied customers recently sent us this message:

“Works great! Yesterday a guy brought in a Dyson vacuum that was clogged. I used the Aardvark to have a look-see — and there it was. A chew toy from his dog that his daughter sucked up. I was able to justify the service fee it would take to get it out. Thanks again for helping an old man with new technology!”
— Mike, Vacuum Repair Technician

This is a perfect example of just one of the many applications for an inspection camera like the Aardvark HD3M.

Ever lost your keys? You know they’re around your office somewhere, but you can’t see them. Try using a wireless inspection camera to find them. In the video below we show what it looks like under one of our desks here at Circuit Specialists.  Well, what do you know — keys!

Look down the kitchen sink drain for the ring you accidentally dropped while doing the dishes. Check inside the wall behind your home theater system to see whether or not there is enough clearance to run and hide AV lines for a cleaner looking installation. Those are just a couple uses for the Aardvark HD3M inspection camera. The possibilities are endless.

What will you find with yours? Get your very own Aardvark HD3M wireless inspection camera.

What interesting ways have you used your wireless inspection camera? Post your stories and ideas in the comments below.

Circuit Specialists employees enjoy a great BBQ lunch!

Once a month the management of Circuit Specialists organizes a nice lunch for our employees.  A nice gas BBQ was purchased recently and we all enjoy the good times spent having some fun around the table and eating a good meal.


Featured on the grill this month was Brian Loeb, President of Circuit Specialists.  He flipped a mean burger!

Visit our website and see our line of soldering stations, power supplies, test equipment and electronic parts..


How to Use a Soldering Iron

Soldering is the process of melting a metal on other metal components to bind the two components together. The most common tool used for this is called a soldering iron.
Soldering is not the same as welding. When you weld something, the components are directly melted together without using solder. Solder is a softer metal with a lower melting point. This allows the components to be connected without using the high temperatures associated with welding and it preserves the integrity of the components. Because solder is conductive, it is widely used in electronics.

Rolls of solder


Using solder to bind things

Solder is the actual material used when binding things together with a soldering iron. Solder has traditionally contained lead, but it is gradually being phased out due to health concerns. Most lead-free solder is slightly more difficult to use than leaded varieties; when melting unleaded solder, the soldering iron needs additional time to recover from heat loss.


Manufacturers of soldering irons use various techniques to make their soldering irons work better with lead-free solder. One strategy is to make the soldering iron heating element more powerful, which helps keep the soldering iron tip at a constant temperature. Other techniques include assembling the heating element and the soldering iron tip as a single contiguous element in order to transfer the heat more rapidly and therefore help maintain the tip temperature.


Using a soldering iron to heat and melt the solder

Most low-priced soldering irons typically heat the tip between 800 and 900 degrees Fahrenheit, so be very careful when using a soldering iron. More advanced soldering irons include a heat control so the user can select a specific temperature for different projects and types of solder. It is important to keep the tip of the soldering iron clean while using it. Common practice is to use a wet sponge to keep the tip cleaned. Clean the tip before you start soldering and continue to clean the tip as you continue the soldering process.


Heat the component, flow the solder

Touch the soldering iron tip to the component you want to solder. After a second or two, introduce the solder to the joint area. The heat will conduct to the solder and cause it to flow. This entire process should only take 3 or 4 seconds, but it is important for the solder to flow to ensure a good electrical contact. If the solder looks like a ball or is lumpy, it is likely a “cold solder joint” and will not conduct electricity. If this happens, reintroduce the soldering iron to get the solder to flow in order to create a good electrical contact


Practical applications for a plastic project box

When Circuit Specialists moved to our new building in Tempe, AZ we noticed our communications closet was getting a bit warmer than we wanted it to be. Rather than spending the time and money needed to route an air conditioning duct into the closet, we decided that just getting some air from the room outside moving through the closet would reduce the temperature by a few degrees, which would be sufficient in this case.

Door fan 1Door fan 1a

There were already two vents installed in the closet door, so we gathered a few parts we stock and went to work. We first mounted two 12 volt DC fans to the upper vent (we also drilled extra mounting holes for two more fans, in case we need them later). We then used a 12 volt wall mount power supply and a small SPDT miniature toggle switch to power the fans.  We mounted the switch and an LCD digital temperature display  — for monitoring the exact temperature — inside a PB-1P plastic project box and attached it outside the door.

Door fan 2Door fan 2a

The DTM0503 temperature display that we used is normally powered by a 1.5 V battery, but we chose to power it with the same DC power supply used for the fans, which required adding a few components to the mix. We used a 1N4741 zener diode soldered in series to the battery terminal on the back of the panel meter to bring the 12 volts down to the 1.5 volts required for the temperature display.

Door fan 3Door fan 3a

Now that everything is installed, we can see at a glance what the temperature inside the communications closet is and turn the fans off to conserve energy whenever possible.

Door fan 4


Wireless inspection cameras are terrific tools for contractors and building inspection professionals as well as do-it-yourselfers doing repairs and renovations around the house. Inspection cameras have become very affordable in recent years and are becoming standard equipment for HVAC repairmen, electricians, mechanics, and plumbers. Any situation that requires observing what is happening in an otherwise inaccessible area can be made much easier with a good inspection camera.

Choosing an Inspection Camera

Let’s start by ruling out any inspection camera that is designed with a 1 meter camera shaft. What good is an inspection camera that doesn’t reach what you want to see?  A good wireless inspection camera should have a shaft long enough to see around corners and underneath objects. A camera with a 3 meter camera shaft is simply more effective than one limited to just 1 meter.

Furthermore, a good inspection camera needs to provide good lighting to produce a good image of the target. Adjustable bright white LEDs are usually placed near the camera head for this purpose. If you do not have adequate light, the image quality will never be good enough. The images or videos captured from an inspection camera should be clear and high quality.

The DeWalt DCT411S1 captures both still photos and video and stores them on a micro SD card. The Bosch PS91-1A is also quite popular and receives good reviews. Prices for these units start at around $200. Ridgid sells an inspection camera with a 200’ reel for around $5,000 for demanding professionals and other high-end users.

A 200’ reel is complete overkill for an average user. Your typical handyman or mechanic can do very well with a wireless inspection camera with a 3 meter shaft as long as it provides sufficient lighting and produces a clear image or video.

Wireless inspection camera

New Trend in Inspection Cameras: High-Definition Cameras that Work with Your Smartphone or Tablet

The Aardvark HD3M waterproof wireless inspection camera is a recently developed camera design that interfaces with the user’s iPhone or Android smartphone or tablet. This inspection camera connects to the user’s wireless device via WiFi and features the desired 3 meter camera shaft length. The camera unit itself acts as a WiFi access point, so it may be used in remote areas where WiFi isn’t available.

The waterproof camera head provides high-definition images or videos (2 megapixel/1280×720) directly to your wireless device and the six adjustable high-intensity white LEDs placed at the camera head provide plenty of light. Most smartphones and tablets have a large high-definition screen, and since the images and videos are stored on the user’s wireless device, it’s very simple to email or text the files virtually anywhere. Perhaps more importantly, since the Aardvark HD3M inspection camera doesn’t have a video screen and doesn’t need a storage card, it is available for a much lower price than traditional inspection cameras, yet it provides superior performance compared to units that cost up to three times as much.

This wireless inspection camera includes a hardshell carrying case and a 3 meter flexible shaft as well as some handy accessories. The shaft diameter is 7.0mm while the actual camera head measures 8.5mm (outside diameter). It can provide crisp still images or videos at 30 fps. The unit runs on 4 AA alkaline batteries.

Buy an Aardvark HD3M wireless inspection camera

Tech Tip: Controlling Electronic Test Equipment with SCPI

The Circuit Specialists CSI3721A and CSI3723A programmable DC electronic loads and the 3631A, 3662A, 3663A, and the 3664A programmable power supplies are fully programmable test instruments that support the standard commands for programmable instruments (SCPI) control protocol. The SCPI standard specifies a common syntax, command structure, and data format for controlling and receiving data from a wide range of test and measurement equipment.


Array 3664A Programmable Power Supply

Because the communication type is not specified by the SCPI standard, you may use GPIB, USB, RS-232, Ethernet, and several other types of cables. Most of the Circuit Specialists units offers feature an RS-232 port, but they can also be used with USB adapters or outfitted with a GPIB interface as a special order.

SCPI commands are ASCII text strings consisting of one or more keywords and one or more optional parameters. Responses to commands such as data or handshake responses can be ASCII text strings or binary data.

SCPI commands either perform a “set”, such as turning a power supply or electronic load on or off, or a “query” operation, such as reading a voltage or current value. In addition to setting and querying in a single operation, SCPI enables you to group similar commands.

Examples of simple command syntax for performing an operation on an programmable electronic load like the CSI3721A are listed below.

INPUT OFF disconnects the load from the device under test.
MODE CCL sets the CC mode.
CURR:0.5 sets current level
INPUT ON connects the load to the device under test.
MEAS:CURR? sends the actual current measured back to the PC.

The SCPI specification provides an easy-to-understand and universal method for controlling and measuring a wide variety of electronic test equipment. Earlier protocols were mostly vendor specific and required a custom user interface to allow computer controlled operation. Circuit Specialists will be providing more test and measurement equipment that adheres to the SCPI protocol in the future as we improve and expand our selection of products.

Simply smart circuitry since 1971.