First off, I'm a software guy trying to learn about hardware, so apologies for nOOb questions...
That said, I'm trying to build the JDuino plan referenced in chapter 6 of the book, and I've run into a bit of a problem. The bill of materials provided in the early part of the chapter doesn't seem to match up completely with the buildout.
The capacitors specified in the BOM are two 10uF 25 V. However, the schematic seems to indicate 220uf 50V and 220uf 10V, in addition to C4 (unspecified) and C2 (.1uf).
Can you help me out with some clarification on what I need? I have the 2 10uF 25V caps, but none of the others. I've soldered most everything else on to my etched board already, but want to make sure I have these right before proceeding.
Thanks in advance!
thanks, still adjusting to getting sleep and whatnot, but all is well.
The capacitor C4 is supposed to be a 0.1uF non-polarized capacitor and is used for the FTDI port... it is only necessary for programming the board using the FTDI cable.
C2 is only used to stabilize spikes in the 5v output signal from the voltage regulator... it is not required, but recommended.
Both C2 and C4 are non-polarized so it doesn't matter which direction you put them in.
The 220uF bulk capacitors are used to provide a buffer for the power supply. One is used from the raw input (+6v to +24v) to keep the voltage regulator supply stable, and the other is used to keep the +5v regulated output voltage stable for the Atmega chip. These are both helpful when using the Arduino board with Servo motors and for stabilizing the input signals from various sensors to keep them from spiking.
Basically, you can use the board without ANY of the capacitors, but when testing various sensors, you might notice some flaky results without them.
I would say go ahead and finish with what you have and add the 220uF caps later. The board will work and you can at least test it out.
Hope this helps and let me know if you have any other questions or concerns.