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61  Using Arduino / General Electronics / Re: Security for Arduino. on: December 04, 2013, 10:08:50 am
Assuming we are not talking anything more than plain vanilla arduino (not DUE or some other larger variant) then we are talking about something like an ATMEGA328.

A commercial design based on a generic Arduino (bootloader and all) is rather crude since it really is just an enhanced development platform.  From a coding perspective, you have made it easy for someone to replace your firmware.  Maybe that is not a concern... but to others it is a big security issue.  You are also subject to any coding errors made by 3rd party library developers.

Consider that the arduino is mostly a "proof of concept:" solution.  A commercial product really should get re-written from the ground up when creating the final embedded device using your own AVRGCC code.

Using the AVR Atmega328, programmed via ISP (maybe carefully crafted in AVRGCC and not using "sketchy" libraries) , without the bootloader, and with security fuse bits engaged means that you have a good standalone solution, that is reasonably secure and you are using the 328 as an embedded controller... as Atmel intended.
62  Using Arduino / General Electronics / Re: Help with transistor problem. TIP120 switching/control circuit for a motor/ on: November 30, 2013, 10:50:04 am
My belief is that they probably worked before you got the wiring right.
63  Using Arduino / General Electronics / Re: Help with transistor problem. TIP120 switching/control circuit for a motor/ on: November 29, 2013, 02:48:23 pm
The diode doe not go across the Emitter/Collector pins... it goes "across the motor pins" from the Battery Source, the cathode end,  and the Collector pin (middle pin)  which is the anode end.
64  Using Arduino / General Electronics / Re: Electrical contact lube? on: November 28, 2013, 10:14:57 pm
I bought a tube at my local Autoparts store after my weather station RJ11 connectors corroded up.  I stuck  a blob onto the connector, inserted it and it has been fine ever since.  (years)
65  Using Arduino / General Electronics / Re: Solderless socket strip on: November 27, 2013, 01:32:54 pm
What I do:

Quick... easy.
66  Using Arduino / General Electronics / Re: interface msp430 with cc3000wifi TI need external components on: November 27, 2013, 01:28:28 pm

Your question is much better answered if you ask it here-->
67  Using Arduino / General Electronics / Re: Unique Serial Number on each of my boards on: November 13, 2013, 08:52:41 pm
The only one that can't be hacked after the fact is the DS2401, since it is mask rom  and non-erasable.
68  Using Arduino / LEDs and Multiplexing / Re: In led matrix display add more than 8 row on: November 12, 2013, 07:06:57 am
Yes, you "daisy chain" the 4017.

See picture for an example:

69  Using Arduino / General Electronics / Re: Shorting Digital Output pins together - ok or not ok? on: November 10, 2013, 07:38:02 pm
And really... with transistors selling for 2 cents each or less in some places... it makes more sense just to by a bunch and build proper driver circuits.
70  Using Arduino / General Electronics / Re: Stranded Wire + Breadboards on: November 07, 2013, 06:49:45 am

The high density male pins work quite nicely for me.
71  Using Arduino / General Electronics / Re: full out output voltage?? on: November 06, 2013, 09:54:55 pm
also, plugging less than 7V DC into the "round" power jack is not recommended, as it will likely be  below the drop out voltage of the onboard regulator.  You don't want to power your board that way.
72  Using Arduino / General Electronics / Re: Standalone ATmega328 + oscillator on: November 04, 2013, 03:05:47 pm
Crystals should not make audible noise.  That seems to be what you are saying.  If it really is... audible...  your crystal is stressed and not working.
73  Using Arduino / General Electronics / Re: What do I need to programatically connect / disconnect 2 wires? on: November 04, 2013, 03:00:59 pm
Standard "American" home Heat/Air Condition thermostats are 24V switch closures.  Meaning... 24 Volts are in the line.  This, to me, qualifies as "higher than TTL Signal level" and a relay is justified as a "switch closure" device.
74  Using Arduino / General Electronics / Re: Control 5v chip on: November 01, 2013, 05:12:49 pm
too  much current causes that.
75  Using Arduino / General Electronics / Re: 7hc595 Voltage Out. on: October 25, 2013, 03:55:28 pm
I think you really need to spend more time learning how things work (be analytic) and less time flailing.  I'm wondering if more complex electronics is not in the cards for you right now.

A BJT transistor is not "driven more" by increasing the voltage.  The Base pin is driven by current... plain and simple.  Using higher voltage only means your don't know what you are doing.   

Draw out on paper what you are trying to do.  Take the time to analyse each problem and solution in your design.  Also, keep in mind that is would be very difficult for a TTL signal to drive a power transistor directly.  This is why you often see a low power, high gain transistor driving a low gain high power transistor. Sometimes a solution requires more than 2 or 3 parts.

Also. if your power source was USB based... there is commonly a current limiting power controller in the path.

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