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256  Forum 2005-2010 (read only) / Interfacing / Re: Automatic door on: January 06, 2009, 02:11:24 pm
Just keep in mind that the device linked to above is a "fail safe" design which is a misnomer if I've heard heard one. By fail safe they mean that your door is wide open when the power dies. Sure, that'll save you if there's a fire but it'll also let any Tom, Dick, or Harry into your house in the case of a power outage. It's better to get a lock which defaults to locked and must be actuated to unlock. For safety there should be an inside latch to open it in case of power outage.
257  Forum 2005-2010 (read only) / Interfacing / Re: Will this power supply work? on: December 31, 2008, 10:06:06 pm
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Oh wait! Positive on the outside? I think that's wrong. !
Can someone confirm for sure whether + or - should be on the outside?

Sigh... You mean I have to get up and walk 20 feet to look at the plug? ;-)

I looked and it is positive center.
258  Forum 2005-2010 (read only) / Interfacing / Re: Will this power supply work? on: December 31, 2008, 10:00:57 pm
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Oh wait! Positive on the outside? I think that's wrong. !

Yes, I'm almost certain that the center pin should be positive and the outer sheath is negative. Totally backwards of the power supply the original poster has.
259  Forum 2005-2010 (read only) / Interfacing / Re: digital tuner on: December 29, 2008, 12:18:14 pm
Anachrocomputer is correct, the mic outputs a very small voltage. But, it's worse than that. It outputs AC. The diaphragm vibrates both up and down. Just look at how sound waves on a scope go both above and below the zero line. The arduino wants 0 - 5V but if you use just a normal op-amp you'd be liable to get -5 - 5V. What you need is to use an amp to amplify the signal up to a maximum swing of 5V and bias it so that 2.5V is the new zero line that the signal crosses. You can do this with amplifiers but you need to be aware of it and plan for it.
260  Forum 2005-2010 (read only) / Interfacing / Re: Frequency Generation of 32.768hz on: July 30, 2008, 04:49:01 pm
Yeah, it would be nice if we could just all agree on a single standard. Of course, neither party is going to want to be the one to concede defeat.

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I often wonder what other differences there are that we should be aware of.  I got caught helping someone on a forum in England in that he was asking a wiring question.  I of course referred to gnd instead of wiring to earth so I felt pretty foolish on that one.

I read an interesting thread on the piclist a number of years ago.

If you have a dangerous industrial machine, in the US you will use green to indicate it is safe (ie stopped), and red to indicate it is dangerous (ie running).

In Europe, you would use red to indicate it is stopped (ie safe) and green to indicate it is running (ie dangerous).

The systems are exact opposites, both make perfect sense, and it could be a matter of life or death to get it right.
261  Forum 2005-2010 (read only) / Interfacing / Re: Frequency Generation of 32.768hz on: July 28, 2008, 08:14:04 pm
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Would be better to write just the number without decimal places if we are talking about integer numbers.

Yes, you are correct. Not using any seperators would be best if the # is an integer. Then there is no confusing between how US people write things and how the rest of the world does.
262  Forum 2005-2010 (read only) / Interfacing / Re: Frequency Generation of 32.768hz on: July 28, 2008, 08:02:11 pm
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I did mean 32.768Khz and not just hz.
If you mean 32768Khz then would be something like 32768000 hz. I guess you cannot get 32768000Hz from a microprocessor running at 16Mhz. I guess you really meant 32768Hz.

This is a real pain in the rear that happens between USA syntax and European syntax. You see, in the US we use . to mean a fraction of a number whereas in Europe you use ,

We use , to seperate groups of thousand powers  where as you use .

So you see, it's totally backwards. When we mean 32768Hz we write 32.768KHz and you would write 32,768Khz

This is REALLY annoying. It's hard to know what people mean when you can't count on the same syntax.

But since we in the US are ALWAYS right you should just get used to it! ;-)
(I'm ducking now and heading for the exit!)
263  Forum 2005-2010 (read only) / Interfacing / Re: Finding pigtails on: July 23, 2008, 06:40:33 pm
I got the tool but I'm having a really hard time using it. I might have gotten some sort of instructions with it but I left them at work... I suppose I'll have to look carefully.

It seems like it doesn't quite crimp tight enough to crimp my molex pico connectors onto 26 ga wire. If worst comes to worst I might try to use something like .006 shim steel to make the tool crimp a little harder.
264  Forum 2005-2010 (read only) / Interfacing / Re: Finding pigtails on: July 20, 2008, 07:26:04 pm
I'm giving that tool a try (just ordered it). It looks pretty similar to the tool I found at Digikey but much cheaper. It can't hurt to give it a try. Thanks!
265  Forum 2005-2010 (read only) / Interfacing / Re: Finding pigtails on: July 20, 2008, 11:04:23 am
Replying to myself...

I still have not found a source for pigtails with the correct connector on them but I did find a fairly cheap crimp tool in the digikey catalog which appears to be able to crimp the ends that I've got.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=AV4999-ND

It's like $60 instead of the way over priced $220 that Molex wants for their crimper.

It appears to me that this $60 crimper will will fine for me. Does anyone think any differently?

Thanks for any information and help anyone can provide!
266  Forum 2005-2010 (read only) / Interfacing / Finding pigtails on: July 19, 2008, 08:19:14 pm
I have need to interface with a module which has a molex picoblade 9 bin connector (the correct interfacing part is #51021-0900) I bought a few 51021-0900 from Digikey and bought the correct pin sockets as well. But it requires extreme skill and patience or a $200 tool to crimp those ends onto wire. I've tried it, I lack the needed skill w/o the crimper. I'd like to find some pigtails with this end on them. I've scoured the internet to no avail. Does anyone know of where I might find such things? Do I really need to break down and buy the crimping tool and some wire? (Well, if I have to go this route I plan to use ethernet cabling as it's about the correct wire gauge and 8 wires. I only really need 6 out of 9 pins anyway...) I've tried looking in the Digikey catalog but haven't seen what I need...
267  Forum 2005-2010 (read only) / Interfacing / Serial communications on: June 29, 2008, 07:13:14 pm
I want to verify that I am understanding this properly...

The serial communications on pins 0 an 1 are in TTL and not RS232 right?

Similarly with software serial, it's not proper RS232 right?

What I'd like to do is interface with a serial LCD (to save on the # of pins needed) and another RS232 device. As such I'd want to use the hardware serial for one and software serial for the other. How feasible is this? Do I need TTL to RS232 converters?

Thanks for any info including pointing me toward where I may RTFM.
268  Forum 2005-2010 (read only) / Exhibition / Re: Solid State Tesla coil on: October 25, 2009, 12:13:41 pm
Heh, I've got to laugh every time I hear or see the term "zero point energy." There are legit uses for that term but 99.99% of the time the person using the term has no real idea as to what they are talking about. Do you really understand quantum electrodynamics?

Also... free energy... really? So all of the laws of thermodynamics are wrong then? Here I thought that energy could be neither *created* nor destroyed. I was also under the impression that entropy must always increase... Boy, don't I feel silly now.

Forget both free energy and zero point energy. Those terms are only useful for fleecing people out of their money.

If I were you I'd spend way more time learning about science and way less time chasing unicorns.
269  Forum 2005-2010 (read only) / Exhibition / Re: Sketchduino (Automated Etch-A-Sketch) on: January 23, 2009, 07:05:24 pm
Usually USB controllers are hard to break. I've shorted a USB port out before and it was fine. Most of them seem to have over current protection that will disable the port temporarily if the controller detects an over current condition.
270  Forum 2005-2010 (read only) / Exhibition / Re: Levitating magnet and improved Serial library on: March 04, 2009, 03:13:18 pm
I know I'm being a bit evil suggesting this but it'd be awesome:

It's much easier to levitate a magnet from above it so... how about upping the challenge by flipping everything over! You'd need more than one electromagnet to stabilize things. Say, 4-8 coils arranged in a geometric pattern. This also has the bonus of allowing the system to intentionally move the magnet around. Imagine how impressed your family and friends will be seeing a magnet run a figure 8 in the air.
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