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22171  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor Knob tutorial problem on: July 14, 2011, 03:28:25 pm
Try running the motor at a slower speed. It can do this if you are trying to go too fast.
22172  Using Arduino / Project Guidance / Re: Power supply decoupling on: July 14, 2011, 03:25:55 pm
Thanks:-

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I can't find anything about the maximum capacitance in the ... data sheet

That is because it is not a low drop out regulator.
22173  Using Arduino / Project Guidance / Re: Power supply decoupling on: July 14, 2011, 03:18:15 pm
Are you sure about the number I can't find a data sheet on an LM8705. Have you got a link to one?
22174  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 14, 2011, 03:12:24 pm
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current draw would be less than 300 mA
Then I don't think it is on. At 300mA for 3 seconds you need 0.18F, and that is the whole charge in the capacitor. You want more than this because that is when the voltage is zero so double it and you get to 0.4F.
I know you can get super caps but I don't think you can get the current density out of them to sustain 300mA.
You would be much better off with a small rechargeable battery that you float charge and then turn off the whole thing in software / hardware after you detect the main power is gone.
22175  Using Arduino / Microcontrollers / Re: Arduino as a Simple Power Source on: July 14, 2011, 03:03:28 pm
Gods are not what they used to be when I was young.
22176  Using Arduino / LEDs and Multiplexing / Re: Help?? on: July 14, 2011, 03:00:19 pm
Either too much resistance or you haven't set the pins as outputs using the pinMode() function in the setup()
22177  Using Arduino / Project Guidance / Re: More is better: I need LOTS of sensors --> Multiplexer? AD Conversion? on: July 14, 2011, 02:59:03 pm
Yes I think these are too slow for what he wants. It is not the quickest of buses.
22178  Using Arduino / Project Guidance / Re: Power supply decoupling on: July 14, 2011, 02:57:59 pm
If you have a low drop out regulator it will say in the data sheet about the maximum capacitance.
Normal values to use on a regulator output is 47uF electrolytic and 0.1uF ceramic on an input 1 to 10uF electrolytic and again a 0.1uF ceramic
22179  Using Arduino / General Electronics / Re: Using only one resistor on a common cathode RGB LED? on: July 14, 2011, 02:55:05 pm
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What sort of things have capacitors in?
Everything electronic.
22180  Using Arduino / Project Guidance / Re: More is better: I need LOTS of sensors --> Multiplexer? AD Conversion? on: July 14, 2011, 02:53:51 pm
Well personally I would just buy the chips and wire them up myself, but I suppose you can get a shield.
22181  Using Arduino / Project Guidance / Re: Providing short term power to Arduino once main power source is turned off. on: July 14, 2011, 01:08:42 pm
You keep saying in line, that implies a series connection, you want a parallel capacitor and diode to stop it discharging back through the turned off power circuit. You need to know the current draw before you can calculate the capacitor size.
22182  Using Arduino / Project Guidance / Re: More is better: I need LOTS of sensors --> Multiplexer? AD Conversion? on: July 14, 2011, 01:05:09 pm
There is only one A/D converter on an arduino and on most other processors for that matter. There is an internal multiplexer. An external multiplexer is not going to slow things down any more than an internal one.
You can get external A/D chips that digitise faster but you will still need to multiplex on the inputs.
22183  Using Arduino / General Electronics / Re: Running 100 LED flashing at specific time intervals on: July 14, 2011, 01:01:06 pm
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i mean the analog pin of the arduino
The arduino doesn't have an analogue pin you can power anything from. The only analogue pin on the arduino is an input.

So you need to run 100 LEDs at a variable intensity with standard 20mA LEDs is this right?

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each LED uses 1.5 v
So they are red?

Do you need to control each LED independently? That is be able to put any number of them on at any time?
22184  Using Arduino / General Electronics / Re: ArduinoUNO and multiple relays on: July 14, 2011, 12:55:34 pm
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, I think, it depends by the VIN power. Am I right?
Yes here is an example:-

http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html
22185  Using Arduino / LEDs and Multiplexing / Re: Help?? on: July 14, 2011, 12:51:18 pm
No as long as they are connected together and not connected to any other signal the it physically doesn't matter where they are. It is only important where the electricity can flow.
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