It is not often an engineer looks at a circuit and says: "OMG, that is so cute!" However, there are no better words to describe the 555SE solder kit from Evil Mad Scientist Laboratories (EMSL). Based on the infamous 555 timer IC, this is a surface mount soldering kit, scaled up from a SOIC package. Not only is it aesthetically pleasing, but it is also functional.
The circuit board is a beautiful dark color with a clear solder mask showing the traces. These surface mount pads allow soldering discrete transistors and resistors. Exposing the functional design in this way makes the 555SE a fantastic learning tool. Also available from EMSL is the 741SE, which is a kit version of the popular ua741 operational amplifier (op-amp).
Opening up the box reveals an inside joke. Surface mount components ship on "carrier tape," which is meant to be handled by pick and place machines. Keeping in line with the up-scaled motif, each electronic part of the kit is labeled inside of a massive piece of carrier tape. The ingenious sorting method helps make it much easier to manage the various surface mount parts.
The well-written instructions logically lead you through its construction. You might be wondering: "how hard is it to solder the surface mount components?" Conveniently, the design only uses transistors and resistors. There are a handful of resistor values, NPN transistors, and PNP transistors. That is it. The component simplicity means you only need to know how to solder two package types: a 1206 passive and a SOT-23. Even with limited surface mount soldering experience or a soldering iron tip that is too large, the 1206 resistors are relatively easy to solder (and very forgiving.)
The SOT-23 transistors, though, do need a sharp conical tip--and some patience. Initially, I tried soldering them with my bevel tip, but it was simply too large for the small leads. Then I tried to use a hot air tool. While it worked out, I could not find a way to apply the solder paste cleanly. EMSL does not provide a paste stencil. However, they do offer a design file so you can create your own stencil.
If you have never soldered surface mount before, I would consider practicing with a lower cost kit first. Or start with assembling the 741SE. It has fewer parts with a little more work room around each. But if time is taken, anyone can solder these kits.
Once finished with the soldering, the mechanical assembly is simple. A snazzy looking anodized aluminum lead frame attaches with four screws. From there, small thumbscrews provide a method for connecting wires. In my test setup, I used male-to-male jumper wires with no problem.
Does the 555SE actually work as a 555 timer? As it so happens, I had a binary counter circuit already wired up in my lab. Its clock signal came from a traditional DIP packaged 555 IC. The 555SE fit nicely on my breadboard, and I was able to "drop-in" the flying lead connections into the existing circuit. And? It worked! I even compared scope measurements between the two. The output of the 555SE is about 100 millivolts less than the integrated version. Not bad performance, not bad at all!
These kits are not the first such products from EMSL. Previously they introduced the Three-Fives and XL741, which are scaled-up DIP-packages using through-hole parts. One notable difference is that the through-holes have extra silkscreen identifying the functional sections of the IC. While sold by Evil Mad Scientist Laboratories, Eric Schlaepfer designed these (and the previous through-hole) kits. You might recognize his name from his MOnSter 6502 project.
The moment I saw the 555SE and 741SE on Twitter, I knew I had to have them! I picked them up from EMSL's store the first day they were available and got to soldering that night. You can grab them from their website for $30 each. For more information, check out the store page for the 555SE and the 741SE.