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1  Using Arduino / Motors, Mechanics, and Power / Re: help with motor project on: July 26, 2014, 06:17:39 pm
i would say start by doing some homework.
1)make sure you know how stepper motors work and what type yours is exactly.
2) look up the datasheet for the uln2803 and make sure it can handle the current drawn by the motor. the datasheet will usually provide you  with enough info to connect it up.
3) learn to use the arduino. work through the examples in the IDE under Basics, Digital, analog, control and stepper. "stepper" should have most of the code you need, the rest you can probably just cut and paste .
2  Using Arduino / Motors, Mechanics, and Power / Re: help with motor project on: July 25, 2014, 11:26:12 am
What questions do you have? Show your code. How do you plan to wire it up? Show a schematic. You could do this with just one potentiometer. When the pot is in the center, the motor is stationary. As you twist the pot off center the motor will spin faster one way or the other.
3  Using Arduino / General Electronics / Re: Uno - how much current can Vin supply? on: July 24, 2014, 04:03:37 pm
Yep that's the idea. It is hard to say what the actual current will be that the vreg will source at 9v. Temperature plays a major role since the regulator will shutdown as it goes into thermal overload. Doesn, t necessarily hurt anything, but it is best to avoid frequently over stressing the part. The Basic rule of thumb is if the part is too hot to keep your finger on, you're probably overdoing it.
4  Using Arduino / General Electronics / Re: Uno - how much current can Vin supply? on: July 24, 2014, 03:45:59 pm
Yes lucky that vreg would power the arduino. If put twelve into the barrel you'll get slightly less than 12 at Vin- no good for addressable leds. Just plug your LED's into the 5v pin. You'll be limited to maybe .5 amp or so from the regulator. Better to just power everything from the 5v source.
5  Using Arduino / General Electronics / Re: Uno - how much current can Vin supply? on: July 24, 2014, 03:14:13 pm
You need to feed 7-12v to the input barrel to power the voltage regulator which can source 800 ma at 5v to the arduino and 5v pin under ideal conditions. Same goes for sourcing power to the Vin pin except you have no polarity protection. You can plug a  well regulated 5 v source directly into the 5v pin and also run your LED's off the 5v pin. If you feed 7-12v into the barrel, Vin will supply about  an amp at whatever input voltage you provide minus .5-.7v loss incurred by the protection diode.
6  Using Arduino / General Electronics / Re: Power Supply questions on: July 22, 2014, 12:01:32 pm
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The leakage current is under 1mA, which means the outputs could be floating
at mains voltage levels if not tied to PE somewhere - recommended unless you have
a genuine reason not to.
I would get shocks from my bench supply because i leave  Jumper wires sticking out of the Ground rail on the breadboard. Every now and then my elbow would brush across one and i would feel a sharp stinging sensation. It took a few times  to realize what was going on.  Probing V- wrt ground shows about a 30 volt difference :/.
7  Using Arduino / General Electronics / Re: Power Supply questions on: July 22, 2014, 11:37:02 am
I would agree with Fungus. "V-" is the DC negative return path which is probably isolated from earth ground . Earth ground should be connected to mains grounding system for safety. In any case Probe it to be sure. Rarely, these cheap SMPS power supplies are dual voltages unless specifically marked. If you use Vin, you best be absolutely sure of your polarity.
8  Using Arduino / Programming Questions / Re: I just do not understand these output voltages on: July 22, 2014, 11:10:47 am
a schematic and picture might be helpful. what value resistors are you using? its always smart to initialize your inputs as well.
9  Using Arduino / Project Guidance / Re: How rugged is Arduino? on: July 21, 2014, 07:09:59 pm
Reliable and rugged are to different things. arduino is very reliable within its specified operating conditions. Outside of its Safe Operating Area- all bets are off. What specific application did you have in mind?
10  Using Arduino / LEDs and Multiplexing / Re: Questions about 1w LED, 0.25w resistors, TIP120 on: July 15, 2014, 02:49:13 pm
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Question 1
the math looks about right. though actual numbers (Vf and R) may vary a little bit. i have bread boarded 1 watt Leds with a bunch 1/4watt resistors for a quick demo, but I certainly would never consider this route for any practical application. Use a constant current supply for optimal performance and reliability. they cost a dollar or two on ebay.
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Question 2
yea on paper looks like it might work but in real life those slight deviations in the actual values can significantly affect the circuit especially when you only have .6v across the resistor(s). And the voltage drop of the tip120 depends on the current flowing through it. Use a cc supply and a logic level FET.
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Question 3
Smoke will happen.  LED = diode. once it turns(@ 3.2v) it  offers practically no resistance and it will let as much current flow through it as the regulator will source burning  the LED up as well as the regulator. there are inefficient ways to use a vreg as cc supply, but just use a constant current  supply.
11  Using Arduino / General Electronics / Re: Slide Switch on: July 10, 2014, 07:23:48 pm
there are many ways to connect a switch. you need to be more specific and include some design parameters. Usually installation goes like: solder it and somehow affix it to the enclosure with hot glue, super glue, screws, duct tape or other.
12  Using Arduino / Motors, Mechanics, and Power / Re: Need help with RAMPS (reprap 3d printer shield for mega) on: July 10, 2014, 11:50:47 am
Yes the motor drivers must be plugged into the female headers on the ramps board and the motors are plugged into the male pin headers. unfortunately I don't think the easydrivers are directly pin compatible with the RAMPS board so will have to figure out how to make the necessary connections between the easydrivers and the RAMPS. or just buy the proper drivers mentioned in an early post.The Ramps board is not a controller or Motor driver per se- the Mega 2560, or sometimes Sanguinolo (sp?), is the controller (which you bought, right?), and the polulo A4988 chips are the drivers. the Ramps board is more or less just an interface board that makes the connections clean and easy.
13  Using Arduino / Motors, Mechanics, and Power / Re: Need help with RAMPS (reprap 3d printer shield for mega) on: July 09, 2014, 10:02:25 pm
Yes you can connect steppers directly to the RAMPS board. Did you by it as a kit for a 3d printer? If it is not part of a kit, you may also have buy the motor drivers.
14  Using Arduino / General Electronics / Re: LM2575 7.4V to 5V (i don't understand the circuit diagram) on: July 09, 2014, 06:15:36 pm
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great potential to destroy your phone, burn your house down, and die a fiery death
-a humorous over exaggeration, don't take life too seriously people. On the hand, if you have never seen what happens to an incorrectly charged lipo, you should definitely watch a few videos on YouTube before you try to make your own charging circuit.
15  Using Arduino / General Electronics / Re: Proper way of reattaching power cord in Ontario, Canada ? on: July 08, 2014, 04:18:06 pm
good link^
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