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31  Using Arduino / General Electronics / Re: relay circuit won't work? Please help on: March 28, 2014, 07:31:54 pm

32  Using Arduino / General Electronics / Re: Drive a led with NAND gate on: March 27, 2014, 08:56:53 am
I wish you luck in your quest to convince the Internet that the 74HC595 *isn't* the key to driving multiple LEDs with Arduinos.

One read of the data sheet will explain why we are constantly abusing this poor IC.  If you draw 20mA per pin off of a HCT device continuously, you will certainly drive it outside the Absolute Maximum rating listed in the Datasheet and assuming harm is not done is just wishful thinking.

And for the curious, I have a retro collection of 74LS family logic chips... some of which I have "tested to destruction" on purpose to see how far outside Max Specs you can go before death.  Most chips are pretty hardy... but I have also seen chips perform ever so slightly differently after being abused if I didn't actually make it release smoke.
33  Using Arduino / General Electronics / Re: Drive a led with NAND gate on: March 27, 2014, 06:18:28 am
<gasp>  Electronics technicians and engineers have been getting it wrong for 50 years.  All those wasted resistors... the horror. <sarcasm off>

Yes, I'm being half serious here and not aiming my comments at you personally, but we constantly see people wanting to skip the current limiting part of a design by employing what I see as misguided rationalizations for why  a simple and inexpensive part can be omitted.

TTL Logic chips deliver logic level *signals* to other TTL logic chips.  Nothing in the design of a standard TTL logic chip is designed to drive non-standard loads (something other than another TTL logic chip) unless the chip has the word "buffer" or "driver" in its name.

Any other implementation constitutes "chip abuse" and while it may not be obvious right away... you are harming the chip (and likely the LED if it is a typical red one) when you ask  the chip output to deliver maximum unrestricted current to an LED.

It's not best practice. A well trained technician or engineer would not do it.   But how you abuse your own chips is your own problem and your own choice... just remember to buy more parts than you need.  And while you are at it, buy a big resistor assortment for say $9.00 and you will be all set for YEARS without having to come up with excuses about why you want to skip using a resistor.  They exist for a reason... Engineers don't design them into circuits to make things cost more or to just annoy people.
34  Using Arduino / General Electronics / Re: [Newb] What salvaged part can be used with arduino? on: March 27, 2014, 05:55:55 am
Learn how the parts work (resistor, capacitor, diode, etc)

Use common sense

Learn how to desolder without destroying ( Solder Sucker, desoldering braid etc)

Build a "junkbox" where you can collect 'sensible' recycled parts

Most of the parts in all of the devices you listed are ASIC  (Application Specific IC's)

Here is a quick guide.  If you can't find a Datasheet on a google search, don't bother.  If your device ran on 3.3V, you will need extra parts to level shift to the 5V of the arduino to make it work.

Best advice I can offer... Find much older electronics to salvage.  Ones that don't have Surface Mount parts... you may still be able to find some.
35  Using Arduino / General Electronics / Re: resistance fail on: March 26, 2014, 12:25:45 pm
A long time ago I did this chart... it might shed some light on what is being discussed.

36  Using Arduino / General Electronics / Re: resistance fail on: March 26, 2014, 09:03:51 am

I want to have a minor objection to a statement you made
I understand giving something too much power and blowing it up

Power = Current * Voltage and it is a measure of "work".

I wish to clarify that providing too much power will not make something fail...  specifically.

You can provide too much voltage with a power supply and get bad things to happen if the load can't regulate that voltage .   You can provide too small a voltage with a power supply and very little will happen.  You can provide too little current with a power supply and likely burn up the power supply...  but you cannot provide too much current.   That is why I object to your statement about giving too much power to a load.   A load will only *draw* as much current as it needs. 

A short circuit is a form of failure where the power source is asked to supply an unrestricted amount of current between the two supply  connections, namely Power and GND.  As if a wire or component of high conductivity is place between the connections.  The unrestricted request for current will usually exceed the capacity of many parts, causing some rather catastrophic failures of at the very least... a fuse.
37  Using Arduino / General Electronics / Re: potting? silicone? epoxy coating? specifics on weather proofing Arduino circuit on: March 25, 2014, 09:15:43 pm
I think the tool dip/spray is called PlastiDip
38  Using Arduino / General Electronics / Re: basic soldering iron - tips and advice? on: March 25, 2014, 05:30:09 pm
If you EVER feel the urge to file your tip because you think it's "dirty" or just not working as good as it used to and you have tried the "normal" methods to prep it for work... D O N ' T!     Go out and by a block of Sal Amoniac.

It's practically magical and lasts for AGES!
39  Using Arduino / General Electronics / Re: potting? silicone? epoxy coating? specifics on weather proofing Arduino circuit on: March 25, 2014, 05:12:03 pm
There are actually multiple choices for standard PCB  conformal coatings from MG Chemicals.

40  Using Arduino / General Electronics / Re: Beginner Question control Power Cable on: March 15, 2014, 10:20:48 am
41  Using Arduino / General Electronics / Re: My circuit on: March 11, 2014, 06:35:52 am
42  Using Arduino / General Electronics / Re: Can U Convert Arduino into Muliti-processor with a shield? on: March 10, 2014, 05:52:04 am
With the right hardware, it becomes somewhat possible... but it will hardly be a the solution for the goal you have in mind...   you will just end up with multiple cores.
43  Using Arduino / General Electronics / Re: Control speed of a DC motor on: March 10, 2014, 05:40:41 am
I think he thought you were OP...

The email is very clear about what is needed "from OP" and to me... not "unpleasant" as you say.

OP   Please answer the questions... or we won't know enough to assist.
44  Using Arduino / General Electronics / Re: Alternative to reed switches in camera control project on: March 06, 2014, 06:59:32 am
Noob error...   he has no idea what he is talking bout... but to me... he is using this:
45  Using Arduino / General Electronics / Re: Power Supply on: March 03, 2014, 08:42:35 am
Hmmm... I'm just saying what was there... I know these things were cheap... but there were 4 1N4001's in a bridge configuration... I agree that a lot of these things would just use 1 diode with a filter cap.
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