As you look through RV-Project.Com and it's videos, you will soon realize that I have several Do-It-Yourself electronic projects for your RV. These projects typically require a minimal level of soldering ability. Truth be told, there is only one way to develop this skill, that is learning by doing. Fortunately there are several "Learn-to-Solder" kits on the marketplace, and a few of them are quite good.

In my projects, I try to build the circuit boards using "thru-hole" technology whenever possible. However, there are two instances where this cannot be done, and a few of my projects use "surface-mount" technology, often called SMT or SMD (Surface Mount Technology-Surface Mount Device). SMD is a newer technology, and newer devices are often only available in SMD packages, so when those devices are used, the only option is SMD. Secondly, SMT devices are smaller, meaning more components can be placed on a givern sized circuit board.

Whenever I use SMT for my projects, I always use the physically largest components I can, which somewhat mitigates having to use those components. And you will find that most of the SMT boards also include many thru-hole devices as well. Most projects then are hybrid in nature.

"Thru Hole" is so named because there is a hole through the circuit board, often with pads on both top and bottom, but sometimes only on the bottom. the parts are attaching by inserting them into the holes, then snipping the excess lead length off after soldering them.

These items are unquestionably easier for beginners. Components are typically larger than SMT, and thus typically are easy to identify, either with a color code or the actual part number printed on the component.

They are also easier to handle, and much easier to solder onto a circuit board.

SMT devices are attached to one side of the circuit board only, using pads that the device is soldered to. They do not have leads, and are typically smaller. Their smaller size usually results in the components being harder to identify.

With SMT technology, circuit boards are often populated with parts on both sides, so for a given board size, you can have double the components... at least in theory.

Many SMT devices are availale in different size packages, including 1206, 0805, 0603, and 0402 to name a few. These numbers correspond to the physical length and width in mils (0.001 in). For example, a 1206 component would be 0.012 long and 0.006 wide.

To solder any component to the board you use a solder, which is a low-temperature melting metal; traditionally comprised of Tin (Sn) and Lead (Pb). You may also find Silver (Ag) and Copper (Cu) in trace amounts. Due to RoHS (the "Restriction of Hazardous Substances" directive of the EU), many companies are going to lead-free solder, such as Sn/Ag/Cu. The melting point for this solder is slightly higher than lead-based solders.

63/37 Solder is slightly more expensive as tin is more costly than lead. Lead-Free even more so. I still prefer the traditional 60/40 solder such as Kester "44".

Solder typically also includes 2% or so rosin flux in it's core. Flux helps to clean the solder joint for improved solderability. There are also general purpose solders not intended for electronic work, such as solder used for copper pipes in plumbing. While this solder must be lead-free by law, it typically contains Acid flux. Acid flux is not appropriate for electronic work as it will damage the metals in the circuit board over time. Rosin flux is the only type that should be used.

Other solders exist as well, such as the type used for stain glass work. This solder is typically either 60/40 or 50/50 (Tin/Lead) and contains no flux. It is also usually larger in diameter. It is just too difficult to use this type of solder in electronic work. Use solder that is intended for electronic work.

Other electronic solder is available such as solder paste, used in automated soldering of SMT devices, or reflow (reworking) operations. Soldering paste works best with hot air guns, not soldering irons. Reflow is an advanced topic so it will not be discussed here.

First and foremost, a good mechanical connection must be made with the two metal parts. Do not rely on the solder alone for the mechanical integrity of the joint.

For printed circuit boards, the physical contact between components is a sufficient mechanical attachment.

For surface mount components, holding the part down with Kapton tape often helps.

For jobs such as wiring speakers, the wire should be fed through the speaker lug and wrapped around to provide additional support.

The basic idea of soldering is to heat the joint first, then apply solder. Do not heat the solder as you apply it; rather feed the solder into the hot joint, letting it melt as it contacts the hot joint.

To accomplish this, touch the soldering iron to the joint first. Then after a second or two, push the solder into the joint.

Heating the solder first then applying it to the cold solder joint can cool the solder off as the joint can act as a "heat-sink". This often results in a "cold solder joint", which has neither mechanical or electrical integrity.

Apply enough solder to fill the entire pad surface and fill the hole (for thru-hole components), yet not so much to create a solder bridge (see below).

When the soldering job is completed, the result should be a concave hill of solder around the lead. The solder joint should also be shiny looking. A dull solder joint is a telltale of a cold solder joint.

To fix a cold solder joint, simply re-heat it. You may need a bit of rosin flux when re-heating as the flux may have been consumed during the initial attempt.

There should be no gaps in the solder "hill", and no solder blobs.

A convex blob of solder typically indicates the solder pad was not hot enough, which can happen if the soldering iron does not touch the pad, or if the temperature of the iron is too low as heat can be wicked away by the circuit board trace (thermal wicking). This most often occurs when soldering grounded components due to the significant amount of metal on the circuit board ground.

Circuit boards for RV-Project.Com projects that require solder connections to ground planes typically have gaps between the pad and ground plane to minimize thermal wicking during soldering.

You can, of course upgrade your soldering iron if you find you want to do these kind of projects. I have used the following soldering irons for years, and I can recommend them all... it just depends on your budget and how much you intend to use it.

Again though, I would recommend you start out with the Elenco AK-100 Soldering Practice Kit. In addition to all of the necessary components to get started, the manual is full of information, including proper soldering technique, parts identification, how to desolder, and repairing circuit boards. A good start for $15.

One word of advice, you can spend a lot of money on soldering equipment, but it is not all necessary. You need a basic set of tools, and everything else is nice to have, but not essential.

The essentials are:

• 25W fixed or (higher wattage) adjustable soldering iron.
• Diagnoal Cutters to cut leads off thru hole components.
• Solder. I prefer Made in USA 60/40 solder (60% Tin - 40% Lead), either made by Kester or MG Chemicals.
• A method of cleaning the soldering tip. Either a Hakko steel wool style tip cleaner or a wet sponge.
• Flux if you are doing surface mount. Electrical solder will include flux, but sometimes you need a bit more.
• Desoldering braid.
• Kapton tape or ESD tweezers for SMD.

For convenience, I am providing a list of the items I use. Of course, feel free to purchase these items from your favorite retailer.

This is sometimes an art in itself. Tip temperature is very important as a tip too cold will not melt the solder quickly enough, and a tip too hot can damage the circuit board or components. However, it is better to have a tip slightly too hot than too cold. A cold tip also contributes to cold solder joints and solder blobs.

A cold tip requires you to keep the iron on the component longer, which tends to heat everything around it, including the circuit board. A hotter tip will allow you to make the solder joint quickly and can be removed more quickly, generally before over-heating the surrounding area.

Also, larger circuit board traces and pads require a hotter tip as they have more surface area to heat. This is also true with heavy gauge wire.

For this reason, I like an adjustable soldering iron. I can lower the temperature for delecate components, and crank up the heat for larger surface area soldering jobs.

If you only have the budget for a single soldering iron, then a 25Watt iron will work. If in the budget, consider a 25Watt as well as a 40-60Watt iron for larger jobs, or an adjustable temperature iron. Personally, I have a half-dozen soldering irons, some adjustable heat, and some fixed.

Some devices, such as integrated circuits can be thermal sensitive. For those components, I like to use a "torque" pattern as if you were changing a tire.

For example, if you have a 14pin integrated circuit, soldering the pins in a criss-cross order will spread out the thermal load on the device.

An arbitrary pattern such as shown on the right will minimize the heat build up in any given area (of course, you would continue soldering with pin 6 through 14 in a random criss-cross pattern).

As well, if you hold the Integrated Circuit down on the circuit board while you stake down the 4 corners, the device will tend to sit flush on the board.

Solder bridges are unwanted solder that bridges the gap between adjacent solder pads. They are caused by too much solder, and the effective removal method is to use a desoldering technique, such as desolder braid or a desoldering bulb.

Sometimes simply re-heating the solder joint will clear the bridge.

Another effective but somewhat dangerous method (so I recommend not doing it) is to heat the solder joint, and while still hot, whacking the circuit board against the workbench. If the solder is hot enough, it will fly off the joint.

This procedure could cause a blob of solder to create a new solder bridge in another location, or you could burn yourself when doing this, or in the worst-case scenario, hit yourself in the eye with hot solder. So don't do it!

Did I mention wearing safety glasses when soldering?

To minimize unintentional solder bridges, RV-Project.Com boards are made with a solder mask (what makes the boards purple) which is a film that covers all non-pad surfaces of the board. It's purpose is to prevent the flow of solder between pads. It is generally effective for all but very close adjacent pads. The natural color of the circuit boards is a pale shade of green.

Sometimes solder bridges are intentional. In a few RV-Project.Com projects we have used this techinque to set particular options on the circuit board by gapping the bridge with a blob of solder.

In the example shown here, the transmitter module voltage is set to either Battery Voltage, 5V, or 3.3V by a solder bridge (only one bridge should be programmed at a time in this example). This allows the circuit board to be used with various transmitter modules that require different voltages rather than having a specific circuit board for each module (3.3V programmed in the example).

When solder bridges are added to the circuit board, the solder mask between the pads is removed, and the pads are placed close to each other; both of which make it easier to create the bridge.

The advantage of this method is the setting can be easily changed at a later date by de-programming the solder bridge with a soldering iron.

Generally the instructions for the kit will include some sort of parts identification and orientation. Some parts are polarity sensitive and some are not.

Typically, resistors, inductors, and small value capacitors are not polarity sensitive and can be inserted into the circuit board either way. However, by convention it is nice to align all of the components so their color codes or other value identification are oriented the same way. This makes for a nicer looking job, and can be easier to later identify part values.

Resistors typically have a color code that makes it easier to identify. However, 5% and 1% resistors usually have different color codes (3 digit for 5% and 4 or 5 digit for 1%). Consult your installation manual for the specific color codes to look for as they do vary a bit (especially for 1% resistors).

Similarly, low value capacitors may have a number that identifies it's value. Again, there are some variances in these codes, so it is best to again consult the installation instructions.

You can also buy an inexpensive color code wheel like the one shown here as well as download an app for your smartphone that will aid you in identifying resistor and capacitor values. This is optional as all of the instructions I develop for RV-Project.Com projects have the color code for each component. Here is an example construction document for RV-Project.Com's LED Super Dimmer.

Standard resistors. the EIA (Electronic Industries Association) has produced a set of common resistor values, called the "E" Series. These are preferred values, and have been selected to provide a minimum number of components needing to be stocked, yet provide a full coverage range. It would not be economically feasible to manufacture every value of resistor or capacitor, therefore the industry adopted a set of common values. For example, the E12 series values assume 10% tolerance resistors, and comprise of 12 standard values per decade. E24 Series are designed for 5% tolerance resistors, and so on.

The E12 series consists of the following standard values: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 as shown below. This seemingly arbitrary pattern does have a method, and that is tolerance. For a 10% tolerance resistor, the furthest values of any two given resistors can be is 20%; assuming the lower value resistor is +10% and the higher value resistor is -10%. Therefore, each value is 120% from the previous value (1.0 x 120% = 1.2 x 120% = 1.5 and so on).

If you have not figured it out, each E-series value has a decade multiplier. For example, E6 would include 1.0, 10, 100, 1K, 10K, 100K, 1.5, 15, 150, 1.5K, 15K, 150K... and so on. So in the range of 1 Ohm to 999K Ohm, the E6 series would consist of 36 resistors, E12 would have 72 resistors, and E24 would have 144 resistors.

It can be hard to find resistor values other than the above examples, but the good news is most electronic components will work with any value resistor within the required tolerance. And you can always find additional resistor values by looking for a higher tolerance resistor (for example, 1% tolerance resistors - E48, would have 48 values per decade).

Capacitors follow similar E-series values, and are determined by their tolerance family.

Some components, such as Electrolytic and Tantalum capacitors do have a polarity (although some Electrolytic capacitors used for speaker crossovers are non-polarized). For such components, the circuit board will have a corresponding mark, whether it be for the positive, negative, or Cathode lead of the component.

The general convention is to mark the Negative lead for Electrolytic capacitors, and the Positive lead for Tantalum. This polarity is very important as if reversed, spectacular smoke may be experienced.

Marking is often done twice. Generally the Negative or Positive side is marked on the component itself, and the negative lead is typically shorter.

Diodes, including LEDs typically have their Cathodes marked. The Cathode in most but not all situations usually goes towards the more negative side of the circuit. However, since this is not always the case, we refer the marking as the Cathode, not the Negative side.

LEDs typically have a shorter lead to mark the Cathode, but typically also has a flat spot on the base of the component. Standard diodes normally have a ring on the Cathode end, but do not have a short lead.

Integrated Circuits (ICs), especially Dual Inline Pin (DIP) typically have a notch or dimple on one end. This is the orientation mark and should match a similar marking on the circuit board. The pins are usually designated Pin 1 to Pin XX (number of pins). When the IC is oriented so the mark is at the top, Pin 1 for the device is usually to the top-left of the device.

BJT Transistors (Bipolar Junction Transistor) used in RV-Project.Com projects are commonly in TO92 packages as shown to the right. There is usually a outline of the case on the circuit board designating the correct orientation of the component.

TO92 packages may also have in-line or "Ammo" pin configuration as shown.

In rare cases, there may only be dot on the board. This dot designates the Emitter lead, and the assembly instructions should show which lead is the Emitter.

Power Transistors. Whether they be BJT, JFET (Junction Field Effect Transistor), or MOSFET (Metal Oxide Semiconductor - Field Effect Transistor) are commonly supplied in the TO220 package. There is typically a metal tab on one side of the device. This tab is marked on the circuit board as shown.

In some cases there will be a Heat sink connected to the transistor. The heat sink is attached to the TAB side.

The assembly instructions will typically show if an insulator is required between the transistor and heat sink, and what hardware, if any, is used.

Here is a typical board you might find in a RV-Project.Com project. You can see the parts layout as well as orientation marks for those components that require the proper insertion. The circuit boards are typically well documented.

I am also providing a list of the various kits I built for this article and video, or equivalent kits I recommend. I show both thru-hull and surface mounting kits. Note that the surface mounting kits typically include additional components should you lose one.

If you don't like any of these kits, there are many others available - and some that are useful, such as AM and FM radios, test equipment, and audio devices. Simply search on terms such as Solder Practice Kit..

Of course there are a great many other items I could recommend, but I really don't want this to be a page full of ads for tools, so I will leave it to you to determine what else you need. Let experience be your guide. You will determine soon enough if you need anything else.

I will at least provide a list of what I have on my workbench, in addition to the tools I have already mentioned:

• Circuit board holder. After using a Pana-Vise and other types for years, I now prefer the cheap ones for cell phones.
• Isopropyl Alcolol. This is a good cleaning agent. Make sure you buy 99% or better (pharmacy rubbing alcohol is usually 40% water).
• ESD Cleaning brushes. For cleaning flux off circuit boards.
• Needle nose pliers. Sometimes you need to bend wire.
• Wire strippers. Used to bare the ends of wire.
• Workbench light. I like the articulating clamp-on LED types that have a ring-light with a magnifier in the center.
• Soldering pad. So you do not burn your workbench.
• Soldering stand - if you don't have one of the soldering station type irons.
• Fume extractor. Keeps from breathing toxic solder fumes.
• SMD Hot Air re-work station. Makes repairing SMD circuit boards easier.
• Spare soldering iron tips. For replacing worn out tips and for different tasks.
• Kim-Wipes. Used to clean circuit boards when using Alcohol.
• Cotton cleaning swabs.
• Precision tools; Jeweler's screwdrivers, file set, X-Acto knife, small flashlight, connector crimpers.

If you build any of the various electronic projects shown at RV-Project.Com, you know they are not offered in a kit. You simply have to buy each component individually from the sources I provide. I do try to minimize the sources I buy from to lessen the burden of purchase. I select the source according to likelyhood of having stock, lowest cost (including shipping), and quality of components (i.e. whether or not components from the Shenzhen Electronic Bazzar will work). Since I am in the US, I reference US based vendors whenever possible. If you are not in the US, you may find a different source works best for you.

I highly recommend purchasing additional components, at least for the lower-cost components. True, you will not likely want to buy more $30-dollar LCD displays than needed, but purchase extra components when they are cheap. For example, you can often buy quantities of 10 or more for less per-piece than one or two. If it costs 2 cents for a component and you need 3 of them, simply buy 10.

You never know - many of my projects use similar components so you might begin building a bench stock if you intend on building several RV-Project.Com projects. As it turns out, the ubiquitous 10K ohm 1/4W carbon-film resistor is used in just about all of my projects, so don't be afraid to buy 100 of them at a time (they cost a penny each at TaydaElectronics.Com).

As well, you will at some point install a diode on the circuit board wrong (and find you need to cut it out of the board), or lose a SMT resistor. Having a couple spares that cost 2 cents each is a lot better than having to pay $10 shipping to replace that 2 cent part you lost.

Even at my experience level, I am sometimes guilty of damaging components.

When you are completed with soldering your project, use the following checklist to ensure you have done everything correctly:

• All component leads have been soldered (you might be amazed the number of times I have missed a lead).
• All solder joints shiny - no cold solder joints found.
• All excess component leads clipped off.
• All polarity sensitive components oriented correctly.
• All components in the correct place - check values.
• No unintentional solder bridges.
• No solder blobs.
• Connections to power correct (Positive and Negative connected correctly).

Only after a cursory check should you apply power to the project.