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436  Using Arduino / Project Guidance / Re: Resistor 2W with LEDs on: February 22, 2014, 11:11:09 am


Using a zener diode and a resistor combo like this could be an option, except you need a string of LED's...

(Fire is unlikely,  but fair enough lol)
437  Using Arduino / Project Guidance / Re: Pull down resistor not working as expected on: February 22, 2014, 10:47:32 am
Does this happen on other pins?

And you're using pinMode (7, INPUT); in setup ?
438  Using Arduino / Project Guidance / Re: Resistor 2W with LEDs on: February 22, 2014, 10:43:15 am
You are going to generate the same amount of heat with any linear regulator method.
If you want to reduce the heat then you have to use a switching regulator, there are a lot harder to make because you need a good layout on a PCB to keep the circuit stable.

Quote
And just to reiterate - using a current source for the LEDs, you do not need to feed them from a voltage regulator.
I think you are misunderstanding this statement.
Quote
So again, the LM317/7812s would go away.
No, you replace it with all those transistors that generate a constant current supply.

I would not endorse the advice given by cjdelphi

He  asked for suggestions... now get off your soap box
439  Using Arduino / Project Guidance / Re: Resistor 2W with LEDs on: February 22, 2014, 10:36:54 am
There is an even easier way....  but you take a bit of a risk as there's no current regulation.

Simply using 1 transistor per string of LED's, you'd bias the transistor with the right resistor value on it's base, and leave out the resistor between the collector and emitter, eg a 2n2222 npn (800ma rating) what (i and probably I alone) i'd do is place different resistor values on the base until you get 1/3rd or so the target current...  once you hit your 100/200/300ma mark (just use a multimeter if you wish to test it) use the same resistor value on each of the transistors.

Cons - current is not regulated, heat will make the current rise, so the trick is to get it roughly 1/3rd of the max current rating, so when the heat does rise, the LED will get brighter but it should hopefully stay within your max range.

Pros. only 1 transistor and only 1 resistor, and cheap.

The better the heatsink, the less likely current will fluctuate with heat, for example i use the same method for 10watt RGB's and it works flawlessly all day every day, i have had it working with 3watt RGB's too but the smaller the LED, the more noticeable the effects.

ie.. winter time, the LED is not as bright, in the summer time, it's 30% or so brighter.

But as pointed out, using a sense resistor, you can accurately measure the current and alter the current accordingly via PWM.
 
440  Using Arduino / Project Guidance / Re: Resistor 2W with LEDs on: February 22, 2014, 04:04:24 am
You could get away with just using a couple of transistors (and a sense resistor) and basically make your own regulator.. but it would be more work than an ln317 in current regulation mode.

441  Using Arduino / Project Guidance / Re: Arduino Uno running in a car on: February 22, 2014, 04:01:52 am
Do MOV (Metal oxide varistor) get produced for low voltage ?   - if the same principal applied to the 120/240ac versions but only in low voltage DC form, that could be used to protect the circuit from voltage spikes.

442  Using Arduino / Project Guidance / Re: An arduino dial up modem? on: February 22, 2014, 03:59:38 am
Nope, turning it into one....

 
443  Using Arduino / Project Guidance / An arduino dial up modem? on: February 22, 2014, 02:21:14 am
Obviously there would be little use for one... but what about feasibility?   Would a 56k (or slower) modem be possible?
444  Community / Bar Sport / Re: Calls "from windows" about "online hackers inside your computer". on: February 21, 2014, 11:50:25 pm
I've always built my own machines so I'd never fall for it  .


But I'd love to have some fun with a scammer over the phone, I'd feed them false information and have some fun!
445  Using Arduino / Project Guidance / Re: Motion detecting to turn on device on: February 21, 2014, 07:06:03 pm
Yes you could....

Desktop or laptop?  (WOL / wake on lan) or button press
Ceiling light - a simple relay .

446  Using Arduino / General Electronics / Re: SSOP to DIP adaptor on: February 21, 2014, 10:40:12 am
http://m.ebay.com/itm/131119281904?nav=SEARCH
447  Using Arduino / General Electronics / Re: SSOP to DIP adaptor on: February 21, 2014, 10:36:06 am
I have a sop8 & sop16 adapters, you drop the chip in which grabs it with a spring and then drop it into your breadboard, no soldering required.
448  Using Arduino / General Electronics / Re: Need idea for voltage threshold switch solution on: February 21, 2014, 10:31:01 am
The transistor is the way, instead of a voltage divider, a zener diode placed backwards on the base pin would keep the transistor off  until the reverse breakdown voltage takes place switching your circuit on, a darlington transistor or possibly a schmitt trigger to keep a clean transition between off and on.
449  Using Arduino / General Electronics / ftdi chips fake vs real on: February 20, 2014, 11:08:28 pm
http://zeptobars.ru/en/read/FTDI-FT232RL-real-vs-fake-supereal


I have wondered, as some chips I've felt iffy about and this article confirms my suspicions about some ebay dealers!
450  Using Arduino / Project Guidance / Re: 1 input - 3 outputs. on: February 20, 2014, 09:18:49 am
You need to take a break judging by the code smiley

Simplify it, break it down.... what I'm confused over is this supposed to be a set pattern? Since there's only one button? Eg  123, 321, 123 looped over and over?

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