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1  Using Arduino / General Electronics / Re: Very simple amperage question on: December 21, 2012, 01:23:41 pm
Thank you!
2  Using Arduino / General Electronics / Very simple amperage question on: December 21, 2012, 01:17:04 pm
Hey guys!
I have an IR reader that needs between 2.7 and 5.5V to function, so I'm just gonna plug it into the 5V port on my arduino.
However, it also has a max supply current of 0.56mA.
Do I need a resistor? Because R = V/I;     R = 0/.00056   =>   R = 0   (?)
Thanks for the help!
3  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 17, 2012, 07:35:18 pm
Oh, I see the confusion. The resistors in the lasers are 130. However, since they're built in, I just need to make sure that 4.5 volts with 15 mA gets to them! So, I can use the built in resistors and just use 8 33ohm resistors to limit the 5 volts from the arduino to each laser (along with each laser's built in resistor) so that each laser/resistor combo is getting 4.5 volts at 15 mA, which is what they'd be getting from the 3 batteries.
The "replacing the resistors already in the lasers" was adding an extra step I didn't need. I think I'm gonna get some friends together and finish this project this weekend. Any suggestions, criticisms, thoughts?
Thank you all for your help! If we get it done, I'll be sure to post pictures!
4  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 17, 2012, 05:05:09 pm
I believe so. When I used my multimeter on 200 for resistance, it showed a steady 130. Does that mean 130R? Or does it mean 130 ohms? or both?
5  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 17, 2012, 04:38:46 pm
So...if those resistors are already in place...Don't I just need 8 33ohm resistors for each of the lasers?
6  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 15, 2012, 07:13:40 pm
So...brown orange brown for the resistor?
7  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 15, 2012, 05:24:34 pm
Ok, I lied. I set the multimeter to 200 instead of 20M and got a pretty steady 130. Does that mean I need a 130 resistor? (With the bands equaling to 13 * 10 to the power of 1?)
8  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 15, 2012, 05:16:00 pm
Ok, so I checked the resistance and it came out as 0.00, so I'm beginning to doubt my "resistor theory". Does anyone know what the piece on top is? Right below the metal rectangle? Thank you!
9  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 12, 2012, 09:03:19 pm
Ok, cool. So I need 4.5 volts at 120 mA with 8 *insert number after I test here* ohm resistors?

Also, why can't I use just one resistor? Wouldn't the voltage or amperage difference be the same after a larger resistor as 8 smaller ones?
10  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 12, 2012, 05:05:19 pm
And you are correct bibre! That's what I'm shooting for.
And thanks! I just found photoresistors and knew that I could make *something* cool. And I wanted it to involve lasers. So I came up with this!
11  Using Arduino / General Electronics / Re: Laser Harp Help? on: October 12, 2012, 05:03:55 pm
Alright guys, sorry for the long wait time. I'm back and ready to work on my harp again. As it turns out, Calc 2 in college takes up a lot more time than you would think. smiley-roll-blue
Anyways, I've been looking at the lasers themselves and they seem to have a resistor in front of the line that leads to the laser, meaning that it needs less power. But they *all* have the resistor (all 8 of my lasers). So here are my questions: How to I tell what kind of resistors they are? I have a multimeter - can I use that? Also: how do I calculate the energy the lasers will need? Is it something like...

Voltage needed by the individual lasers (so, if they each need 4.5 volts, I need one 4.5 volt wire)
with
the amps each laser needs * the number of lasers (8 lasers, 15 mA each, so 120 mA)
and
one resistor equal to the voltage of the resistor already in the lasers BUT equipped to handle 120mA

Is this correct, or am I missing something? Thanks for your patience and help all!
12  Using Arduino / Sensors / Re: Ambient Energy? on: August 14, 2012, 11:17:11 pm
Right, we wouldn't want to become one of those forums where the last post is always "Hey! I got it working! Thanx!" that you find when you Google a problem... smiley-roll-sweat
Sorry for the long response time, I was on a vacation.

I actually did what fkeel recommended, and he was correct in his assumption (connecting the resistors to zero the analog inputs out). That worked, as well as grumpy Mike's link to the arduino keypad tutorial (which, really, I should have looked there first...) worked charms for actual, simple use in a program!
13  Using Arduino / General Electronics / Re: Laser Harp Help? on: August 05, 2012, 08:31:17 pm
Thank you! And actually, I do want them all on at the same time. I'm on vacation, will  update I get back and play around with it.
14  Using Arduino / General Electronics / Re: Laser Harp Help? on: August 03, 2012, 11:02:27 am
Considering this is a first time, mostly "just because" project, a couple hours should be fine for me, and it's nice and simple because I have the holders, and I know it'll work perfectly. I don't expect this thing to be on more than about 10 minutes at a time.
How would I go about finding a 9-volt power supply that plugs into a wall? Are they called something particular?
Also, why a pair in series and four pairs in parallel? I would only want 8 actually, but why that configuration, instead the 8 in series as suggested earlier?
15  Using Arduino / General Electronics / Re: Laser Harp Help? on: August 02, 2012, 08:43:50 pm
Our assets consist of my Arduino Uno, 8 laser pointers (In varying stages of being taken apart), varying photoresistors, and a breadboard to put them all on (I'll move onto an actual board when I'm done with the planning). I would power the Arduino with a 9-volt battery, and I don't believe I have any regulators or transistors at my house. I could pick some up at Radioshack though...
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