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166  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.
167  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.

168  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.

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

170  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?
171  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!
172  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 .

173  Using Arduino / General Electronics / Re: SSOP to DIP adaptor on: February 21, 2014, 10:40:12 am
174  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.
175  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.
176  Using Arduino / General Electronics / ftdi chips fake vs real on: February 20, 2014, 11:08:28 pm

I have wondered, as some chips I've felt iffy about and this article confirms my suspicions about some ebay dealers!
177  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?

178  Using Arduino / Project Guidance / Re: Consultation required on Arduino powered Android controlled car on: February 20, 2014, 09:09:36 am
A way of amplifying your signal.. transistors or a darlington array or fets... then protection in the form of a flyback diode for inductive spikes which can kill your transistors/uno.
179  Using Arduino / Project Guidance / Re: You have a way to go! on: February 20, 2014, 09:06:23 am
That's a little overkill.... but yeah that would work fine.

Umm, no, it won't!  smiley-eek

The reason for the Zener in my circuit is to protect against over-voltage to voltage regulator input


Well now, firstly you have the Zener the wrong way round - it will simply directly conduct and blow the fuse.

So, connect it the right way round?  No.  You specified a 1N4732, which is a 4.7V Zener which will again, conduct heavily and blow the fuse.  Were you even to connect it to the output of the 9V regulator (or even a 5V regulator), it would draw a heavy current and shut down the regulator.

Arguably, a 1N4745 specified at 16V would be appropriate.  On the other hand, better to make it more like 27V, a 1N4750 which will clamp at a voltage the regulator is stil rated (35V) to handle comfortably (at least as a transient).

I did not see a zener voltage so I figured it was a fast switching diode.. my bad
180  Using Arduino / General Electronics / Re: Problem of Arduino sharing ground pin on Darlington array chip ? on: February 20, 2014, 04:09:57 am
Placing a diode backwards across the motor will help reduce spikes, I stay away from motors but some people place a small ceramic across the motor  (not entirely sure except  protecting the electronics?)
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