Tuesday, February 26, 2013

Blue is Terrible

This is a quick follow up to my post a few months ago about Sharpie Gel Highlighters.

At the time I wrote the post, I was still ecstatic over the discovery of this wondrous innovation. Now, after I have had a chance to use more than just the yellow one, I'm going to reply with the sage advice won from experience.

These are the best highlighters I have ever used, with one small exception.

The blue one is awful. After I took the following picture, I threw the blue one away.

The purpose of a highlighter is to draw attention to things. The four other colors are brilliant and obvious.The blue one can barely be seen on paper.

If anything, the blue shows up better in the above picture than it does in person.

I now understand why I couldn't find the five color set in stores. If you are going to buy them, go with the four pack. It has yellow, orange, green, and pink. All four of these colors are vibrant and easy to see. Don't spend the extra money to get the blue one. It is not worth it.

Tuesday, February 19, 2013

Soldering Irons

One of my readers asked the question recently:
What do you use for soldering?
That was a topic that I hadn't thought of writing about. Today, I fix that.

Soldering is a vital skill for playing with electronics. Breadboards and twisting wires together are useful for prototyping, but they will only get you so far. They leave much to be desired when you want something reliable and durable.

Soldering is one of the best ways to make electrical connections. It is easy to learn, and all it takes is a good bit of practice to become proficient.

But, I have to admit that decent tools make it much, much easier to learn.

Like many, I started off soldering with a very cheap soldering iron. It was old, underpowered, and not temperature-controlled. But, it was free.

There are several problems with cheap soldering irons. If it is a low-wattage model, it will take a while to get up to temperature. Trying to solder with an iron that is too cool can actually increase the likelihood of damaging some of the more delicate and temperature sensitive electronic components. The iron is too cool to melt the solder effectively, but it is hot enough to cause harm. This is usually made worse since you will be holding it against the part you are trying (and failing) to solder for a much longer time than usual.

If it is overpowered, or if even a lower-wattage one is left on for too long without using it, it will get too hot. This will make it more likely to damage things as well. Using an iron that is too hot has caused me to lift the traces off of a circuit board more times than I would like to admit.

That is what I started with. I currently own three different soldering irons:

My workhorse is a Weller W60P purchased from Altex for about $70. (As a side note, Altex is one of my favorite stores. It is one of the few remaining electronics stores that still sells soldering tools and equipment. However, they no longer carry this model.)

The W60P is 60 watts, so it has plenty of power and heats up in about a minute. It has a temperature-controlled tip, so it never gets too hot. I have never damaged a circuit board using this iron. It is a joy to use.

The only problem with the W60P is that the temperature-controlled tip doesn't get hot enough for some of the higher temperature solders used in some electronics. It is not adjustable without replacing the tip. This is why I have a cheap backup for when I need something hotter.

My high-temperature backup is a Craftsman model 113.540420. This cost about $12. It is 45 watts and without temperature control. It gets more than hot enough to work with high temperature solders.

I have the third soldering iron for portability. Sometimes it is terribly inconvenient to be tied to an electrical outlet. For those situations I have a butane-powered BernzOmatic Soldering Torch purchased from Lowes. It cost about $20. It can get very, very hot. It is suited more for soldering wires than for delicate work. It is incredibly convenient to have around. I use it mostly for working on my car, since I don't have the luxury of a garage or outdoor outlets at my apartment. The hot knife tip is also useful for cutting nylon rope.

Since it doesn't have a built in igniter, I keep a butane lighter stored with it.

That is my fleet of soldering irons. Note that the cord to the W60P is not in the best shape. It turns out that using something that gets over 700F near a cord that melts around 320F can be problematic at times.

This is why it is important to have a proper stand. In addition to avoiding melted cords, the stand also prevents the soldering iron from rolling off the table. Since things like laps, legs, and feet are typically below the edge of a table, and soldiering irons are incredibly hot, the importance of a stand cannot be overstated.

Don't forget to dampen the sponge for periodically cleaning the oxidized solder from the tip of the hot iron.

This is another useful and inexpensive tool to have around. Everyone needs a helping hand every once in a while. It takes one hand to hold the soldering iron and a second to hold and apply the solder. That doesn't leave many hands to hold the work. Most of the time it is ok setting the work on a table. However, sometimes things need to be positioned or held more precisely.

There is one other thing that is required for making a good solder joint:  good solder. I prefer small diameter solder 0.025" or so. It should be rosin core for electrical work. Never use acid core solder. Acid core solder is only for plumbing or structural applications.

60/40 lead/tin solder is good. 63/37 lead/tin solder is better. The 63% lead and 37% tin alloy is the eutectic mixture of these metals. This means that there is a single melting point instead of a melting point range. For any other proportion of lead and tin, one of the two metals starts solidifying first and then the other. If the work is disturbed while the solder is partially solidified, you get a poor connection. Using the eutectic alloy reduces the chances of this happening.

Also, this is a good time to note that you are playing with lead. It is not the friendliest heavy metal out there. Always work outdoors or with proper ventilation. Wash your hands. Eat elsewhere.

When soldering, you will often have the need to de-solder something. My favorite tool for this is solder wick. This is a fine braided copper wire saturated with rosin flux. If this is placed over a solder joint and then heated with an iron, it wicks up the solder and removes it from the joint. This is surprisingly clean and easy to do.

 The other option for removing solder from a circuit board is a solder sucker. It is a spring loaded plunger with a Teflon tip that can withstand high temperatures. You compress the plunger until it clicks in place. Then you melt the solder joint, quickly place the tip of the solder sucker into the molten solder, and press the release button on the side. This releases the plunger and the spring pushes it out causing a rapid vacuum action. This sucks the solder right out of the joint... in theory. I haven't had the best luck with this. Sometimes it works for me, sometimes it doesn't. The tip tends to clog with hardened solder and requires occasional cleaning. I tend to prefer the solder wick.

That sums up my arsenal of soldering equipment. Every tool is not necessary, but each has its uses. This is probably a much longer answer than that reader expected from such a simple question, but it turns out that I had quite a bit to say about it.

Tuesday, February 12, 2013

FrånkenLämp Update

It has been over two months since I committed to posting updates at least every other week.

This has been working rather well for me. It's about time that I updated the banner on the site to reflect this fact. I try to stay a post or two ahead, and I have been occasionally inserting smaller updates on the off-weeks.

This is one of those smaller updates. It is a follow up to the two-part FrånkenLämp story.

Part I inspired this comment:
...You'll laugh, you'll cry, you'll wish it was already Tuesday after next to read part two of the FrånkenLämp adventure. Critics are calling it "the most thrilling quest for accent lighting of our age."
And the conclusion inspired this one:
It's here! The thrilling conclusion to the FrånkenLämp saga. Critics are heralding it as: "Poignant. An accent lighting adventure to end all accent lighting adventures. A coming-of-age lamp tale that is both riveting and thought-provoking."

Both comments were from the person for whom the lamp was being constructed... So she may have been slightly biased...

I am happy to say that she is very happy with it (if you couldn't tell by the comments above). Here is an artfully staged action shot of  FrånkenLämp in its new home:

Tuesday, February 5, 2013

Useful Power Supply

I enjoy playing around with electronics. One thing that most, if not all, electronics projects need is a good power supply. Some projects are more forgiving than others, but many have strict demands on things like voltages and current.

Obsolete computers tend to provide a wealth of interesting and useful pieces. For example, every computer has a power supply. Most are of a surprisingly high quality. They supply a number of set voltages, usually with the ability to supply a surprisingly high amount of current. They use standardized connectors which can also be scavenged from old computers.

Mine is rated for 28 amps at 3.3 volts, 40 amps at 5 volts, and 30 amps at twelve volts. In comparison, the typical power supply used to charge a cell phone is rated to supply only 1 amp at 5 volts.

Many electronic circuits do not require heaps of current. But that is the beauty of the thing. A circuit will only pull as much current as it needs, and it is convenient to have the excess current available when it is needed. Like when trying to power ridiculously large stepper motors... but that is hopefully the subject of a future post. For now we focus on the power supply.

A computer power supply can be much more cumbersome than is desired for use on an electronics bench. By my count, there are typically somewhere around 50 individual wires sprouting out of the side. More modern versions (ATX) don't even have a power button. They will not turn on unless connected to a computer's motherboard. Conveniently, these limitations and inconveniences can be overcome.

Lets start with turning it on.
There is a 20 pin or 24 pin connector on the power supply. This is how it connects to the motherboard on a computer. One of the wires going to this connector is green. If you connect this wire to ground, the power supply turns on. When you disconnect it, it turns off.

With this knowledge, a switch can be added to turn the power supply on or off. Or, the green wire can be soldered to ground, and the power supply will turn on whenever it is plugged in.

Next, let's get rid of most of those unnecessary wires.
For my purposes, I only left a few of the 4-pin connectors in place. This gives me access to 12 volt (yellow) and 5 volt (red) power. I also left one of the 6 pin connectors in case I needed 3.3 volt (orange) power. With the power supply unplugged, I opened up the case and removed the main circuit board. I then cut off or un-soldered the unneeded wires.

In the picture below, you can see several of the ground wires (black) cut off almost flush with the circuit board. (Above the leftmost corner of the fan, next to the mounting screw.)

An important detail is that there are three feedback wires on the 20 or 24 pin connector. These are smaller diameter wires that connect to the same pins as three of the standard diameter ones. There is one for each of the three main voltages. These must remain connected to their respective supply voltage for the power supply to continue to function. You can see below where I shortened these wires so they would fit inside the case and soldered them to the appropriate supply wires. You can also see some red and orange wires that could not be cut close to the circuit board. These were left longer and the cut ends were insulated with heat-shrink.

The last step I performed was to add some additional connectors.
When prototyping, it is often convenient to be able to supply power to the bare end of a wire. I had the following set of connectors that I rescued from some broken speakers. When you push on the lever, you can insert the end of a wire. When you release, it is held tight. A standard 4-pin female connector was added so that it could easily be plugged in to the power supply. Below are top and bottom views.

I then attached the connectors to the top of the power supply with some double-sided foam tape.

You might note the comment written in Sharpie on the top of the power supply. When using old computer power supplies there are two weak points. One of them is the cooling fan or fans. The fans ran whenever the computer was on, and as a consequence they can be dusty, worn, and noisy. If the fan fails, there is the danger of overheating the power supply. To prevent this, I placed a drop of fresh oil on the fan bearings when I had everything disassembled. This should help preserve them and allow them to continue to cool the power supply. 

The second weak point in some power supplies are the electrolytic capacitors. Due to poor manufacturing, there are many capacitors that fail before they should. Before going through all this trouble, a check should be made that the top of the capacitors in the power supply are not bulged, domed, or leaking. The top should be perfectly flat. 

There are many other how-to articles on the web that discuss re-purposing a computer power supply. The power supply can be modified in a number of ways, depending on your needs.  This is one good example. The author gives a brilliant tip on modifying the fans to run on lower voltages to reduce noise. This is a great idea if you don't plan on using too much current and dislike listening to the whir of a loud fan.