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1  Using Arduino / Project Guidance / Re: How to measure the frequency of a AC sine wave signal? on: October 28, 2013, 02:00:51 pm
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Haw! That's cute as hell.
2  Using Arduino / Installation & Troubleshooting / Re: pc doesn't recognize arduino as arduino on: October 03, 2013, 06:24:20 pm
And don't upgrade to windows 8 !
3  Community / Bar Sport / Re: Little physics brain teaser on: August 30, 2013, 07:18:27 pm
It doesn't seem to follow Ohm's law.
4  Using Arduino / General Electronics / Re: A question about solar panels on: August 06, 2013, 10:52:20 am
There are numerous tutorials on how to interface battery storage with solar panels. Most of the weather stations you see advertized have this setup.

 Some of them are pretty cheap and even include data storage, wireless connection and processing software. Might be better to just throw some money at it if you are serious about gathering weather data.

Google is your best friend in learning electronics.
5  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 26, 2013, 01:40:47 pm
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I think that the bottom line is that it is fine using aids to calculation but you need to be able to tell if the result is wrong for what ever reason, be it malfunction or user error.

And it doesn't matter if that aid is log tables, slide rule or electronic calculator.

When I was a G.A. in grad school I had a prof who insisted we we sum up test scores in our head, when we graded papers. Since the numbers were never more than two digits, it was pretty easy. However what I do now is take lots and lots of percentage compositions. like  1209.4/5321.8
I really can't see using long division to get the answer.
6  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 22, 2013, 11:03:15 am
I agree with you liudr Scientists and engineers... and pretty much every one else need to be familiar with basic math. The point is that the rote memorization of times tables and the ability to do long division on a piece of paper is no longer as important as it once was.

I agree, it seems like there is far less emphasis on science and math in schools. Back in the 1960's when I was in school, even the local Junior collages were offering four full semesters of calculus, chemistry and physics. Now this is condensed into one or two semester overviews. Also the inflated grad system was not in place. If you got and A or B in these courses , you deserved it.
7  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 21, 2013, 08:04:05 pm
I can still add, subtract,multiply, divide but a hell of a lot slower than I used to. I also used to use Log tables and a slide rule. The sad (or happy) fact is that I no longer have to know any of these things. Calculators and computers have made these manual processes obsolete. And how many engineers won't tip their hats to spell checkers. Now I can write a an intelligent looking document without spending half my time in a dictionary!

I'm thinking that this will only get worse with time. The question is; does everybody really need to know how to do simple math by hand? It's fine to know the underlying theory but how many real world situations do you run into where you can't grab your nearest electronic crutch and type in the numbers?

When I was in high school. You were not allowed to use anything but a pencil on any kind of test, now most places allow calculators, and why not. This is the twenty first century. The paradigm has shifted.
8  Using Arduino / General Electronics / Re: Controlling a 5v relay, only getting 2.4v? on: June 28, 2013, 01:03:44 pm
It's such a simple circuit. seems like something must be mis-wired. make sure you don't have the transistor hooked up backwards. In bread boarding, I've done that more than once. check the ohms on your resistor, it's easy to mistake orange for red. Not much else could be wrong.
9  Using Arduino / Project Guidance / Re: How to Waterproof TMP36 temperature sensor? on: June 18, 2013, 01:47:56 pm
That probably will be OK, the body is sealed, but you might as well coat the whole thing. it will end up having a little slower temp response, but then you know the wires are completely sealed.
10  Using Arduino / Project Guidance / Re: How to Waterproof TMP36 temperature sensor? on: June 17, 2013, 08:06:05 pm
Nicks idea is best but if you  already have bought them then just coat them with epoxy like the manufacturers do... are you sure that they are not already water proof?
11  Using Arduino / Sensors / Re: Thermocouple + MAX31855 + Arduino--SPI wiring Problems on: March 28, 2013, 07:48:02 pm
You should not have done any harm  unless you connected the MAX chip directly to the 5 volt outputs of the Arduino.  What voltage are you reading across the MISO connection? Do you ever get any other reading than the base reading?

12  Using Arduino / Project Guidance / Re: K Thermocouple+MAX31855+Arduino Mega Problem-PLEASE HELP ME!!! on: March 26, 2013, 05:22:01 pm
I had a similar problem even when all the connections were soldered to a perf board. I think this chip is very sensitive to noise. I added some extra bypass caps but that did not improve much. I went to much higher temperatures than you did and got larger swings as the temperature increased. Also got some very high and low spikes. As the temperature went up, the readings were pretty much where they should be but drifted high and low in sort of a random way, so the chip was working but picking up noise somewhere.

I was told that the voltage divider might be the problem and maybe a level shifter might do better, but I never tried it.

Hope you have better results than I had.
13  Using Arduino / Sensors / Re: Thermocouple + MAX31855 + Arduino--SPI wiring Problems on: March 26, 2013, 01:13:42 pm
The reason I said this is because I checked all the connections and they looked good, but the damn thing still didn't work. What happened is that I put just enough pressure on the open pun, to have it make contact with the solder beneath it. When I took off the probe, the pin opened again.

I probably would still be scratching my head except I saw the Arduino readout change if I pressed on the chip.

I had no problem with the 3.3 out to the Arduino. but I fried a chip by allowing 5 volts in, so make sure you use a voltage divider or level shifter.

Even after I got things running I still had problems with seeing large swings in output that got worse as the temperature rose. I never did track it down. I went back to using a AD595 that had no stability problem.

 
14  Using Arduino / Sensors / Re: Thermocouple + MAX31855 + Arduino--SPI wiring Problems on: March 25, 2013, 04:41:18 pm
I would make sure that you  have a good solder joint in the SOIC to DIP. use a straight pin contact to the top of the pins of the SOIC  and the regular lead to the DIP. so that you are seeing if the continuity is there. I found an open this way that was pretty elusive.
15  Community / Exhibition / Gallery / Re: Glass Kiln Control on: January 17, 2013, 09:03:14 pm
are you using the MAX31855 chip the older MAX6675. I have built kiln controllers with both and I am having stability problems with the MAX31855 chip that I didn't have with the MAX6675. the 31855 displays rolling temperature oscillations around a correct average that increase as the temperature gets higher. it seems like the fluctuations are around 10% of the actual temperature.   Also I see random scrambled readings. 

I have also used AD595 chips, and have had no problem... nice and quite. Have you run into this problem while you were shaking out your system?

I hope you can get the bad links back on line, I'd like to see your code.

I use a laptop to control and log the the results of the run graphically. If you are interested in trying it I'll send you the app and the Arduino code I am using.
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