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1  Using Arduino / General Electronics / Re: Question about resistor tolerance on: February 25, 2014, 01:52:42 pm
If you just want an LED as an indicator rather than to get a particular light level out of it, an order of magnitude over value is near enough.  Just stick a 1K on it, it will light and the current certainly isn't going to damage it.  In fact for many digital applications an order of magnitude (10:1) is near enough.  Its only comparatively recently that resistors with better than 10% tolerance have become affordable, +/- 20% will work for almost anything no matter how tetchy.  I've some 'water clear' LEDs in my box with the almost standard 20mA current rating that light convincingly with a 10k resistor on 5V.  Given a forward voltage of 2.2 V it means they light with a mere 280 uA of current.
2  Using Arduino / Installation & Troubleshooting / Re: Cannot connect to Arduino Uno serial port on Ubuntu after various tries on: February 19, 2014, 06:19:35 am
All I did on my 12.04 was to make sure the dependencies were in place, add the user to dialout and use the package off the website.  It just goes after that.   I'd try another lead and another Arduino, it might yield some clues.  Or program it elsewhere to put something out of the serial port and see if you can read it with a shell script or something.   Its all about clues.......
3  Using Arduino / General Electronics / Re: 5v wall wart as digital input on: February 17, 2014, 01:12:09 pm
Sounds like an expensive and stilted solution to a problem.  Personally I'd use a neon indicator across the pump and use a phototranny to detect if it were on or not.  Nice optical isolation to keep the dangerous stuff away from the signalling.....
4  Using Arduino / Project Guidance / Re: Arduino VCC connected to 10v supply with voltage divider connected to Ground? on: February 11, 2014, 02:24:53 pm
No.

The current pulled by the Arduino will seriously affect the voltage on the voltage divider, you can't pull any real amount of current from a voltage divider without having a ridiculous amount of current flowing through the 2 resistors (ie very low values and high power dissipation).  It doesn't matter that you're using the ground pin, the current used by the arduino will skew the voltage.  If you're using an old school Uno/Duemilanove/Etc with a built in voltage regulator, just feed the 10V into the power jack and let the Arduino sort it out.   You could pull 10V out of the Vin pin.  
5  Using Arduino / General Electronics / Re: Cheap Uk Supplier for 2.54mm Header Pin Connectors ? on: February 06, 2013, 09:06:04 am
http://www.bitsbox.co.uk/connectors/header_con.html
6  Using Arduino / Installation & Troubleshooting / Re: This problem for people about "Not in sync" error. Any updates? on: December 14, 2012, 04:23:17 pm
I have a Chinese knock off, it works as well as an Italian one.  If swapping chips around points to the chip, burning a new bootloader on it tends to sort things.  Its not too difficult is you've got another working Arduino.  Reading the 'ArduinoISP' sketch in the examples in the IDE yields clues or http://arduino.cc/en/Tutorial/ArduinoISP .
7  Using Arduino / General Electronics / Re: Superglue instead of solder? on: December 06, 2012, 01:49:19 am
Wirewrapping is quick & easy. A good solder joint starts with a good mechanical joint - wirewrap makes that mechanical joint to start, and is quick & easy to change/fix if needed.

Not so quick and easy if you solder it after wirewrapping.  smiley  I'd have doubts whether you'd ever get it apart again.......
8  Using Arduino / Project Guidance / Re: Reading more than one sensor in one analog pin on: December 04, 2012, 06:19:02 am
With a RC circuit its possible to 'emulate' an analog input with a pure digital pin with the 'R' being made by your nail in the soil.. In simple terms you set the pin to output, set it high to charge the capacitor, switch it low and then to input and time how long it takes to discharge to the point where it registers as being a low.  The lower the resistance of what is connected to the pin, the quicker it discharges.  You'd need to use something (multimeter or an analogue pin) to determine an approximation of 'R' the (resistance of your nail through the soil) to determine a suitable value for C.  Plenty of stuff on google to work it out but heres a start : http://www.allaboutcircuits.com/vol_1/chpt_16/4.html.  The digital input will register as low when it reaches approximately 2.5 volts.  This probably appeals more if you're a cheapskate...........  smiley-wink
9  Using Arduino / Installation & Troubleshooting / Re: 3.3V output only giving 2.55V on: November 24, 2012, 10:14:29 am
The default Analog reference is to use VCC which is nominally 5V but in actuality is whatever is coming out of the USB port of the computer.  If you plugged the 3.3V output into the AREF pin of the arduino and told it to use it

Code:
analogReference(EXTERNAL);

It will be reading a voltage relative to whatever is going in the AREF pin (3.3 volts if you connect it to 3.3 Volts).
10  Using Arduino / Project Guidance / Re: Questions about Arduino on: October 28, 2012, 12:11:35 pm


Lesson one : The chip circled in Red on the Pi is surface mount (a SMD - Surface Mount Device). The chip circled in blue is what used to be standard many years ago - a through hole chip mounted in a socket which is soldered on the reverse side with the legs of the socket going through holes.  They are relatively easy to mess around with a soldering iron and cheaply available stripboard or home made circuit boards. SMD needs specialist gear that a hobbyist isn't likely to have (or even afford).  In a mass production environment, the SMD lends itself to automation and hence cheap to produce in quantity.  
11  Using Arduino / Project Guidance / Re: Real time wireless video on: October 28, 2012, 11:53:29 am
Quote
My question is could the arduino wifi sheild transmit real time video to a laptop via a router on a wireless LAN network?

Not a hope in hell, the arduino lacks the required horsepower to process video in real time by several orders of magnitude.  Assuming you're connecting an arduino to said wifi shield of course....
12  Using Arduino / Installation & Troubleshooting / Re: Complete newbie - completely thick - LED not lighting! on: October 28, 2012, 11:46:41 am
It doesn't matter which you connect the resistor to, it will work on either, the LED still needs it's longer leg (the Anode) to the positive end of the circuit however. 
13  Using Arduino / Project Guidance / Re: Questions about Arduino on: October 28, 2012, 11:40:21 am
I have around a dozen Arduinos including thiose I made myself, owning more than one is very useful, especially when it comes to burning bootloaders (google it) and trouble shooting.  One of my dozen is an SMD clone, it has its uses but I can't take the chip off it......
14  Using Arduino / Project Guidance / Re: Questions about Arduino on: October 28, 2012, 11:33:08 am
Depends on whether you want to pull the chip out of it or not......

I don't own a Leonardo, but I know they don't do an old school 28 pin chip in an old school 28 pin socket version.  They used to do a SMD (surface mount) version of the arduino Uno, I don't know if its still available.  

If you wanted to take a surface mount chip off a bourd it involves special kit and melting solder.......
15  Using Arduino / Installation & Troubleshooting / Re: Complete newbie - completely thick - LED not lighting! on: October 28, 2012, 11:26:55 am
The old tutorials should have been updated or removed years ago.  I've been around Arduninos a while, but I never owned one I didn't make myself that didn't have a built in LED on pin 13.
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