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61  Using Arduino / General Electronics / Re: Arduino High pins supplying less then 5V on: February 13, 2014, 04:27:03 pm
Because the arduino pins employ mosfet push/pull drivers, there is pretty much no way you will get exactly gnd or vcc potential out of a pin. You will have potential loss due to passing through the active transistor at the pin in the chip.  If your mosfet is behaving wildly different with only a small [few millivolt] difference, then i say... you are using the wrong mosfet.
62  Using Arduino / General Electronics / Re: Optimal communication between Arduino and Raspberry Pi on: February 11, 2014, 07:08:43 am
This all implies that somehow your data will get corrupted or "bit slipped" in transit.  That is actually something I have not seen for months with my Arduino connected via USB to a HUB on the Raspberry Pi.  In my case, I just "send the data" as an assembled CSV "string".  No preamble, No checksum.    The only check I do is to verify that the CSV string contains the correct number of "fields".

In this same configuration, the arduino can regularly ask for a "time sync" for the software RTC running on the arduino (so I can show time on the arduino LCD.  When the Arduino sends an ASCII "bell" character, the RPI sends back a serialized timstamp used to synchronise the local clock.

In none of these situations have I needed to add any sort of extra packet overhead while running at 9600.  So, while you could get all fancy with a packet approach, I'm here saying... you don't really need it...  so really, you are doing it because... well, because you can.
63  Using Arduino / General Electronics / Re: connected the wires wrong power pins on: February 09, 2014, 06:42:15 pm
Yes "it would be fail"

You have probably killed all of the devices that expect no more than 5 volts on your board.  1) the AVR chip used by arduino and 2) the device used to create the USB-Serial adapter.

Best advice: buy a new board. 
64  Using Arduino / General Electronics / Re: Transistor Question on: February 02, 2014, 07:35:25 pm
Read up on how PWM works.

65  Using Arduino / General Electronics / Re: Ethernetcable and Dupont Connectors on: January 27, 2014, 06:46:49 am
As a general rule (but exceptions always exist), you would have MALE pins on a PCB and Female pins on a cable.

I must misunderstand you since I don't quite follow your statement; "I thought the housings were uni, and the pins are male/female."     It is true that they will accept either pin style... but male is far less common. 

Males sticking out of the connector are just... well,   odd.  (unless you need them that way, of course)
66  Using Arduino / General Electronics / Re: help with shift register on: January 15, 2014, 06:38:29 am
It's also common to use the 595(output) in combination with the 166(input) sharing the same control bus (data/clock/latch) thus keeping the directional parts separate.
67  Using Arduino / General Electronics / Re: Relaying/switching 2000w at 240v on: January 10, 2014, 09:12:26 am
This is what you want to use.  And add a heatsink.
68  Using Arduino / General Electronics / Re: negative wire problem on: December 27, 2013, 10:18:07 am
Where are you getting such bad ideas about how transistors really work.

Your drawing is wrong,  For one, you are missing a base current limit resistor.  Are you sure you have a PNP transistor?  Because that is what you have drawn... and that would be the wrong part here.

69  Using Arduino / General Electronics / Re: Choosing BJT or MOSFET on: December 24, 2013, 07:49:37 pm
So let's put this out there.  Using a MOSFET does not make you more "cool"  but it can make your motor driver run cooler.

A good designer uses the right tool or part for the job at hand.
70  Development / Other Hardware Development / Re: Breadboard compatbile ATmega1284P board with V-USB on: December 20, 2013, 06:46:37 pm
And it's even pretty...

71  Using Arduino / General Electronics / Re: XBee RSSI out to Arduino Mega on: December 19, 2013, 07:45:26 am
Unless you are playing with different crystals, PWM won't frequency/period change.  I mean, you can manually change it... but that requires code.  The PWM hardware and the UART hardware are isolated and one does not affect the other.
72  Using Arduino / General Electronics / Re: Lithium cells / batteries. More efficient to step-up or step-down on: December 19, 2013, 07:05:56 am
For what it's worth, here is my opinion.

 A switching regulator in a step down configuration is usually 80-90% efficient in most cases.  You will not get that kind of efficiency from a step up or boost scenario.  In simplest terms, if you boost the voltage, you get lower instantaneous current.
73  Using Arduino / General Electronics / Re: my display lights some LED's very lightly and it should'nt do that on: December 15, 2013, 10:39:45 pm
A "schematic" is still our language... no matter how much time it takes.
74  Using Arduino / General Electronics / Re: Smaller alternative to breadboard? on: December 13, 2013, 08:19:17 am
Note: I think Coding badly pasted badly... :-P

These work too...

AKA  Dolphin Multiwire splice connectors... used in telephone industry.
75  Using Arduino / General Electronics / Re: Transistor as two diodes on: December 13, 2013, 07:43:32 am
More stuff you didn't need to know...  when the team at Bell Labs told their boss they had success in the lab, he was supposedly not pleased... he wanted them to show him a Field Effect Transistor and not the transistor we now know as  Bipolar Junction Transistor.  The BJT was proven to have the characteristics they wanted (signal amplification) so it was a success and announced to the world a month later.
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