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46  Using Arduino / General Electronics / Re: Crossover component on: August 23, 2014, 09:05:27 pm
You're for it now! Your fingerprint is on the internet   smiley-wink
47  Using Arduino / Programming Questions / Re: Trouble with millis() on: August 23, 2014, 08:48:21 pm
And take out all those blank lines. They add nothing and make your code more difficult to read.
48  Using Arduino / Project Guidance / Re: How to power the Arduino from a UK light switch on: August 23, 2014, 08:17:45 pm
Absolutley not.

Lightswitches in uk no not have a neutral.
The box behind the switch MAY  have a neutral running through it, but as you say, it's NEVER connected to the switch.
If you use the earth the very best situation would be you trip a leakage breaker if you have one.
They are not connected to lighting circuits in domestic situations any way.
All the circuits, including the lighting, in my house run through a leakage breaker in the fuse box. Damned annoying if it tripped after dark, until I installed a battery emergency lighting system.
Worst case various electrical devices in home will suddenly become live wrt local earth, FATAL.
No quibble there.
49  Using Arduino / Project Guidance / Re: Another multiples LEDs blinking question on: August 23, 2014, 07:39:32 pm
1) Look up 'blink without delay' in the learning  > examples pages. Read it, understand it and adopt it.
2) Look up 'State Machine' in the same pages.
3) Look up 'array' in the reference page.

We're not going to write your program for you (unless you're willing to pay) but, if you get stuck, we'll help you sort out your errors.
50  Community / Bar Sport / Re: Why Q for transistors? on: August 22, 2014, 09:49:36 pm
I guess "T" was already taken?
Transformers were invented before transistors.
51  Using Arduino / General Electronics / Re: Bread Boards & wishful thinking? on: August 22, 2014, 09:33:12 pm
 What voltages, other then the obvious 3.3 & 5vs, would be desired and at what amperage?

For me, 12V @ 1.5 - 2.0A would be useful, others might want 24V as well.
52  Community / Bar Sport / Re: Winter vs Summer on: August 21, 2014, 10:51:45 pm
London had hail a week or so back, its the middle of summer.
It's not uncommon to get hail in the summer.
53  Using Arduino / Project Guidance / Re: teaching arduino to high school students? on: August 21, 2014, 10:21:17 pm
We still haven't heard from the OP about how much time and equipment is involved. Four weeks could be anything from 1 hour a week for 4 weeks to 4 weeks * 5 days * 6 hours. The former wouldn't give time for anything but the simplest of projects, but until he gives us more details, we're just guessing how complex it can be.
54  Using Arduino / Project Guidance / Re: Does anyone notice Keyboard.begin() Keyboard.end() not working right? on: August 21, 2014, 09:40:57 pm
delay() only takes ints, so delay(.5) is nonsense.
55  Using Arduino / Project Guidance / Re: teaching arduino to high school students? on: August 20, 2014, 10:10:34 pm
The application that we often see is traffic lights. You don't say how much teaching time you have in those 4 weeks, but I suggest just one light running through all the phases* would be do-able in the time available. Before they start programming, get them to write down all the states in order (not forgetting the 'wait' states), so as to get them thinking logically about the problem. After they've completed programming the one light, you could ask them what changes would be needed and how they would implement them (not the code, just the basic method) for a pedestrian push button controlled crossing. Extra points if they remember the walk/don't walk lights and the bleeper for the visually impaired. 
I don't think you'd have time for a full cross roads junction (with filter [turn] lights) system, but you could, at least, get your students thinking about the problem.

If you had even more time, I would suggest a lift [elevator] system. With that, you not only have lights (floor indicators and 'lift coming') but also motion. The more floors, the more complex the problem!

How about an after school club for the more interested students?

*See the 'blink without delay' example in the IDE and also look up 'State Machine' and the switch-case construct in the reference pages of this site.
56  Community / Bar Sport / Re: Music & Electricity on: August 19, 2014, 09:30:56 pm
Shocking! But did the orchestra play at a higher AMPlitude after that?
57  Using Arduino / General Electronics / Re: Pull-up interference from DCC system? on: August 19, 2014, 09:20:14 pm
I'd keep all the electronics as far away as possible from the point motors, especially if you're using the solenoid type. Those give one heck of a magnetic kick when they're activated. I'd also suggest keeping all your electronics away from the track too, near to the edge of the baseboard (or, my preferred option, on the floor in a grounded metal enclosure). Then run your twisted pair or shielded cables to the points and signals at right angles to the track, as already suggested.  Remember that your rails are acting like a very long aerial.

58  Using Arduino / General Electronics / Re: Pull-up interference from DCC system? on: August 19, 2014, 08:53:11 pm
Or you can run the drill backwards a little bit to lose the torsion. 
Then you have to remember to twist it more than you need before turning backwards. But stretching sets the twist tighter.
With short lengths a hand-drill gives much more tactile feedback.
I wouldn't like to use a hand drill on 50' lengths.    smiley-roll-blue
I hope you didn't have to strip and solder them too!  (Or make litz wire!)
I wasn't trusted with a soldering iron then! No Litz wire either, thank goodness. I hear it was nasty stuff to work with and the soldering technique was a severe fire hazard. Plunging hot wire into methylated spirits [Sterno?] isn't a good idea!

They mainly made speaker enclosures with crossovers. The demand was so slow that the testing bods found time to turn their green screen circular oscilloscope into a TV, but no sound. That was in the days of single channel monochrome 405 lines TV (early 60s).
59  Using Arduino / General Electronics / Re: Pull-up interference from DCC system? on: August 19, 2014, 07:59:59 pm
You can easily make twisted pair using a hand-drill and a bench-vice.
My first vacation job was working in a small electronics assembly plant. I spent some of that time making twisted cables (2 to 5 strands) by tying one end of the cables to some fixed point at one end of the factory and spooling about 50 foot out to the other end. I then placed the ends in the chuck of an electric drill and turned it on until the cable was twisted enough. The trick, to prevent the cable from untwisting, was to take it out of the chuck and pull hard, to stretch it slightly. That was the fun bit. I then spent the rest of the day cutting it up into 6" lengths.  smiley-sleep smiley-sleep
60  Using Arduino / Programming Questions / Re: FSM diagrams: states and transistions on: August 19, 2014, 07:24:34 pm
In a "pure" state machine, the "fade" part would consist of multiple states, with boring transitions.
(LED10% -> LED20% -> LED30% -> LED40% ... unconditional, timed.  The process where a single state sits there and changes outputs is NOT "pure")
 Agreed, but I termed it 'an unsteady state'.
(of course, this level of purity can be annoying to implement...)
This would lead to the banishment of the for loop and further leads back to assembly language programming... smiley-eek-blue
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