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871  Using Arduino / LEDs and Multiplexing / Re: 10 Watt high power LEDs. on: October 23, 2013, 08:18:37 am

Here's the breadboard version and very dodgy connections, i'll ramp it up two - three x the power tomorrow when the paste fully sets.

872  Using Arduino / Project Guidance / Re: Newbie guidance for dslr timelapse controller (use relay or transistor?) on: October 23, 2013, 03:27:25 am
Electrons flow the least resistive path...

If your Arduino GND and battery GND are not connected there is no path for the electrons to flow, it's all about the voltage differential between point A and B, the greater the differential the more current will flow, the Transistor when switched on via the base controls how much current flows between the Collector and Emitter, the more current greater the current flow.

But, no current will flow IF the grounds are not tied because there's no "path" or voltage differential for the electrons to flow.

Arduino Pin Out --- [1k] ---- Base Pin (of Transistor)

+ Collector (of your Camera)  (+ side of your button)
- Emitter (of your camera)   (- Side of your button)

When the transistor conducts, a path will be made and you can think of the + and - from the camera "making contact" like a push of a button.

Now, if there's no resistor your camera flash side (which i highly doubt) you could create a short... but don't worry because a "short" is what one would do everytime a button presses to trigger the flash on the camera, so there has to be a resistor there.

A relay could induce a high voltage and do something damaging to your camera.
873  Using Arduino / General Electronics / Re: Transistors - what is the collector/emitter voltage drop? on: October 23, 2013, 01:46:43 am
Take a look a screenshot.

Thing is the voltage drop varies between transistors and the 2n2222 is guilty of a higher voltsge drop.
874  Using Arduino / General Electronics / Re: Still learning resistors on: October 22, 2013, 10:57:21 pm
You could if desperate do this... but any voltage drop would quickly result in less than desired results.

First image shows a circuit which uses a voltage divider with a 9v input and delivers  7.5v  ar 51ma..

2nd image 159ma with adjusted voltage divider to deliver 7v... it should work providing the input voltage stays constant, otherwise buy a regulator or zener.
875  Community / Bar Sport / Re: why do leaves reflect green light? on: October 22, 2013, 10:24:27 pm
The rest of the spectrum means little in this example... i'm concerned with visible wavelengths...  or rather what they do absorb vs what they do not....

876  Using Arduino / Programming Questions / Re: LED pin 13 output voltage on: October 22, 2013, 10:09:58 pm
Is there a transistor driving the led on pin 13?

What LED?

It just activates a 5V relay, well, it's supposed to anyways!

Unless i've gone mad and been dreaming, pin 13 when high activates the smt led on an Arduino.

877  Using Arduino / General Electronics / Re: Still learning resistors on: October 22, 2013, 08:30:07 pm
Point 1:
Voltage drives current.

If you stick a resistor from a 5v supply to ground, you will have 5 volts across that resistor.

Assuming the supply can source sufficient current, you will then have:

Current = 5/Resistance
{*This is called a 'Constant Voltage' supply*}

Nope, this is constant current.

If your supply hits its current limit, what will inevitably happen (assuming nothing cuts out or breaks) is that the supply voltage will drop such that the supply voltage becomes

Voltage = [Current Limit] * Resistance
{*This is called a 'Constant Current' supply*}


Point 2:
The voltage may not be exactly 5V from your 5V supply. That rating is nominal, i.e. it will be that voltage +/-some%. If your multimeter is 100% accurate then your supply is 4.98 - i.e.  -0.4% from its nominal value.
878  Using Arduino / Project Guidance / Re: Turn off arduino by software on: October 22, 2013, 08:13:25 pm
As far as i'm concerned when it's on doing nothing it's practically off, current draw is less than the battery discharge cycle..

Ie, battery loses more power than the atmel processor consumes, the linear regulator, usb chip, led, etc are the power monsters.
879  Using Arduino / Programming Questions / Re: LED pin 13 output voltage on: October 22, 2013, 08:09:25 pm
Is there a transistor driving the led on pin 13?

If not 5 - 2 for the vf of the led... 3v out.
880  Using Arduino / Project Guidance / Re: Hardware ideas for power outage notification? on: October 22, 2013, 08:02:49 pm
If the wallmart spit out 5.8v for example ...

I know vcc can just about handle a 6v input, wether or not a digitital pin can handle 6v .. no idea.

But, place a diode or 2, to lower the voltage or a voltage divider, or a zener... if you're worried, if digitalRead(wallmartpin) is HIGH we have power, you might wish to use a capacitor to stop any unwanted noise which might give a false reading along with a bleed resistor or it will think power is on when it's not... a 1k resistor would give it 2 - 3 seconds or so to make sure power is really off not just flickred on and off .   After the cap bleeds, arduino sees low and you do what you need.

I can draw a circuit....
881  Community / Bar Sport / Re: CPU used to cook with? on: October 22, 2013, 07:41:44 pm

That's scary......
882  Community / Bar Sport / Re: why do leaves reflect green light? on: October 22, 2013, 07:36:53 pm
From the link Paul__B posted:

Not all wavelengths of light can support photosynthesis. The photosynthetic action spectrum depends on the type of accessory pigments present. For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with peaks for violet-blue and red light. In red algae, the action spectrum overlaps with the absorption spectrum of phycobilins for red blue-green light, which allows these algae to grow in deeper waters that filter out the longer wavelengths used by green plants. The non-absorbed part of the light spectrum is what gives photosynthetic organisms their color (e.g., green plants, red algae, purple bacteria) and is the least effective for photosynthesis in the respective organisms.

I read that.... but again, this is *now*  back before plant life made it onto earth/rock. . Back way back, plants did not require humans due to the fact co2 was pretty much everywhere, we could have seen red or blue ..

So that begs the question of all the wavelengths .. why green? (Yes yes i know WHY scientifically) but not from an evolution design point.... the green is right smack in the middle of the visible wavelengths, also our strongest visual color.

883  Using Arduino / LEDs and Multiplexing / Re: 10 Watt high power LEDs. on: October 22, 2013, 07:25:29 pm
A 50 watt RGB led mood lamp (flood lamp) ....

And an arduino smiley
884  Community / Products and Services / Re: New Book, Programming Arduino Next Steps on: October 22, 2013, 11:14:40 am
Looking at the TOC i think you got most of the useful content covered, i'm intrigued  smiley-grin nice work smiley
885  Community / Products and Services / Re: Introducing the ATtiny85 ISP! - ISP and prototyping board for ATtiny85 - OSH! on: October 22, 2013, 11:11:43 am
I've thought about this one a lot... prior to your thread.

The perfect attiny85 tool consists of...

An atmega surface mount with a preloaded (or diy) arduino as isp, 1 micro usb interface (to upload your attiny sketches) and aziff socket to prevent damage from over use.

Step 1. Insert attiny into an attiny85.
Step 2. Set to arduino as isp, etc etc.
Step 3. Upload.

Take attiny85 out, anywhere anytime.
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