Next phase produces a L298 based motor controller circuit. The circuit is mainly based on the datasheet, spiced with an additional electrolytic capacitor and a filter capacitor and the recommended schottky diodes. The layout design for perfboard took a really long time, as I tried to minimize the amount of jumper wires and board area. A really useful tool for layout design is the Eagle, which freeware version I used on Ubuntu. Despite its somewhat weird GUI, experimenting with different component layouts is quite easy. Beside the schematic and layout editors, the Eagle has also a circuit verifier/simulator, which finds out mistakes in schematic before they produce smoke on the real life.Here one can see the too heavy duty rectifier diodes I chose.
Perhaps on next time, I read the component datasheet also on the physical measurement section too. These 1N5822-diodes have really thick (around 1,5mm) leads, which required some drilling to install on a perfboard. As a positive side, this was a good excuse to get a miniature power drill:)Underneath the components there is the board layout design. At least for me, the schematic diagram itself is not enough to build a board, but the layout diagram helps on building and testing the connections.
On the diagram there are a few mistakes, which I corrected to board, but not yet to the Eagle. For instance, there is one electrolytic capacitor too much on the L298 chip power supply side, which I considered a good idea at first. After studying the electronics a bit further from a excellent tutorial, I got worried for the inrush current draw and left it out.
Phew, it is ready for testing.And a peek to under the skirt. Perhaps it is not ready for beauty contest, but the functionality is more important than form.
While soldering the first contacts, my relatively cheap soldering station first tip died. I don't know, if the top coating was corroded due to lead-free solder, touches with kynar wire insulator or what, but it really became resistant to solder. The tip rejected the hot solder like it was a mercury and also lost its heat when in touch with component leads. There are a few places in board,where this really frustrating situation can be seen.Lesson learned, after changing the tip to a new one, I now tin the tip always at the start and end of burning session and also time to time, when needed.
Here are couple of pictures of the Seeduino Mega with the additional connector added. I wrote about it on last entry, but forgot to add pictures.
