Assembling parts onto the SORKIT1 controller board.
If you have purchased the SORKIT1 here at CircuitGizmos, or even if you purchased the parts somewhere else, you might be interested in the Gizmo build of the circuit board controller. The Society of Robots instructions here have a handful of steps for building the $50 robot. Steps 3A, 3B, and 3C have to do with making the electronics of the robot. Step 3B specifically is the step that has to deal with building the controller board. The Society of Robots step 3B also shows board assembly if you have a 10-pin AVR programmer, where here in this blog the 6-pin programmer is used.This blog entry will highlight steps that will help make your controller assembly a little more likely to succeed.
You should also read the step 3B documentation on the SoR website along with these instructions.
Mounting the DIP socket:
Above you can see the DIP socket placed on the PCB. Solder the DIP socket in place, but leave the Atmel AVR ATmega8 (the microcontroller) out of the socket for now. Pin 1 on the socket is identified in the top diagram. The hole location on the PCB is H-12. The PCB bottom side diagram also shows the pin location for when you are soldering. Note that the diagram of the bottom/solder side of the board looks like it has copper donuts. This is to make it easier to see the silvery pads where a soldered component is placed compared to unused locations.
Pins with too little solder:
If you have tinned the board like the last blog entry encourages you to do, then soldering the pins of the DIP socket is easier than if you have not tinned the board. The picture above shows the component soldered in place with perhaps the bare minimum of solder making the connection. You can see “missing” areas of solder.
Pins with the right amount of solder:
This picture shows a well-soldered component. The solder forms a cone around the pin of the component. The cone should have nearly flat sides. A little concave is ok, as is a little convex. Personally I start with a little concave and add solder later if needed. You can think of this as a straight cone with a little volume removed so that the sides cave in ever so slightly.
Do not make balls. If you have made a ball of solder on your connection, it is more likely that the blob of solder will short to the next pin. Or will melt and join with the next pin as you solder the next pin. If you end up with a ball you can remove a little of the solder with the solder braid that I mentioned in the last blog.
Headers mounted on board:
The pictures above show the locations of the headers used to connect to sensors, as well as the servos. Note that the board picture shows the LED and resistor in place along with two capacitors. The graphic only shows the headers and DIP socket. Getting the headers and the DIP socket in place – in the correct places – can be the most problematic thing about parts placement. The top side graphic shows you where to place the pin headers including the 6-pin programming header.
The bottom side graphic shows the soldered locations of the headers and also shows which pins are soldered together. For example, the graphic shows that the pins in column D are all soldered together with a thin wire. You can use a single strand from some stranded wire to do this. For example of you strip the insulation off of some #22 stranded wire and then untwist all of the copper strands you will have many pieces of thin copper wire.
D13 is connected to D14, D15, D16, and D17 by this thin wire. None of these locations connects to any of the soldered locations in column E, though. If they do, there would be circuit problems. You can use the solder braid to remove and “solder bridges” between two pins that should not be connected together.
Also see that H13 connects to F13 across the unpopulated G13. This is OK. A little bit of the thin wire makes the connection between H13 and F13 over the pad of G13.
Above is a picture of the bottom side of the board with the DIP socket, the headers, and some components soldered in place. The layout, with the exception of the 6-pin programming header, still follows that of the step 3B on the SoR website. Note the ground and 5V connections between the headers, the DIP socket, the parts, and the 6-pin programming header.
Next blog: Specifics of the 6-pin header.
SoR Kit assembly, Part 3