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61  Using Arduino / Sensors / Re: K type thermocouple on: September 13, 2012, 08:01:33 pm
Go with what Jack pointed out. Its self contained and uses a digital readout. Google MAX31855... there are lots more at possibly better prices... if you don't mind waiting for a slow boat from China.

There are several  scripts ready to go. Just remember that the digital inputs from the Arduino have to be 3.3 volts, not 5 volts.
62  Using Arduino / Sensors / Re: Potentiometer with Seven Segment Problems on: September 13, 2012, 07:45:16 pm
The logic was  a little off, but it looks like it should work.  Put a longer delay between the states so you can see what is going on,

void loop()
buttonValue = analogRead(pot);
// the way you had it the code would always display "one"
if ( (buttonValue >= 0) && (buttonValue <= 127) )

else if ( (buttonValue >= 128) && (buttonValue <= 255) )

63  Using Arduino / Programming Questions / Re: Doing 'log' maths without a log function on: September 13, 2012, 12:39:54 pm
This seems to work pretty close to what the table shows

void setup() {

double Alt;
double PF= 450;
double PS=1013;
double div = -6.8755856E-6;
  double param, result;
  param = log10 (PF/PS);
  result = pow(10,param/5.255856)-1 ;
  Alt = result/div;
  Serial.println (Alt );


void loop() {

  //do nothing
64  Using Arduino / Project Guidance / Re: Hydrometer on: September 11, 2012, 10:49:11 pm
The point is; unless you are trying to automate the process of taking hydrometer readings, and maybe logging them, It's easier just to buy an ordinary hydrometer.if you are going to automate readings then A Hall sensor sounds like it will do the job. Remember though, any hydrometer ONLY measures density, it does not directly measure alcohol content, though that may be the major contributing chemical in the solution.
65  Using Arduino / Project Guidance / Re: Remotely control a transistor as voltage regulator on: September 11, 2012, 10:39:38 pm
I made a quick search about programming microcontrollers but couldn't find much when it comes to OSX.
Do you have any recommendation?
Or is it better if when the time comes, I move to windows to make this step?

I don't know about OSX, I have only used the Arduino on windows. You might move to windows to start because the windows IDE is very stable and easy to use. There are lots of samples of code that can be easily adapted to what you want to do. What I do is use the arduino board to burn the script into the ATmega chip and then just use the chip on a perf board with whatever components I need....Fast,Cheap and Easy.
66  Using Arduino / Project Guidance / Re: Hydrometer on: September 11, 2012, 10:28:58 pm
Not sure, from their notes it didnt sound like depth or being fixed was an issue
Depth is not an issue, temperature is and there are fudge factors to compensate...if you know the temperature at the time of reading. also, gas bubbles may be a problem as rarman stated. Even plain old sealed tube hydrometers are sometimes a pain to use. I used them for wine, but never for beer, and never with an actively fermenting solution.
67  Using Arduino / Project Guidance / Re: Remotely control a transistor as voltage regulator on: September 11, 2012, 10:18:42 pm
I do not need an arduino to send or receive the signal. I should be able to use/program just a microchip and add few components.
I believe I should be able to decide to use arduino to send signal if needed and not use arduino to receive it.

This is true, but starting out with the Arduino might be the best bet to get the project off the ground without having to learn a whole lot of stuff about programming and microprocessors you might not care to learn. Then, if you want to, you can just prototype up the bare bones chips to do what you want it to.
68  Using Arduino / Project Guidance / Re: Electromagnets to stir water on: September 09, 2012, 08:17:49 pm

When I was doing chemistry these Teflon coated stirring bars were much better than a direct motor driven. They might be better than a ball bearing. They pretty much stay fixed above the external bar magnet and you don't need a lot of logic to get them to spin and the other magnets stay on the outside. Since they are Teflon coated, they won't scale up or corrode in the boiling water. The bar magnets to drive the stirrers can also be purchased. I was always were stirring through glass, but you should be able to get enough penetration of thin stainless to pull it off.

69  Community / Exhibition / Gallery / Re: Warning! One Million Ohms on: September 04, 2012, 03:58:44 pm
Of course! IT BLINKS! Now all you got to do is add an IR sensor and a audio module that cry's DANGER! DANGER! when someone gets to close.
70  Community / Exhibition / Gallery / Re: Warning! One Million Ohms on: September 04, 2012, 01:39:29 pm
Why all the components on the bottom...smoke and mirrors?
71  Community / Bar Sport / Re: What is the most expensive board you ever smoked? on: September 03, 2012, 11:17:55 am
$160,000 in total damage isn't quite your $300,000 threshold, but it was real damage to production environment equipment and actual repair dollars that had to be paid.

I think I need to step aside for Oracle. Replacing the board on the machine I fried wouldn't even come close to $160,000.
72  Community / Bar Sport / Re: Inventor of the 555 chip dies on: September 01, 2012, 08:43:37 pm
I wonder if he knew that he invented the chip that gave the most fun to the most people ever. Is there any old timer out there that has not tried some form of the 555 atari-punk?

I made two portable units for my kids and they drove my wife nuts smiley-evil
73  Community / Bar Sport / What is the most expensive board you ever smoked? on: September 01, 2012, 08:36:45 pm
Just got to thinking. There were a number of new post form people who zapped their motor shields. I thought it might make them feel better to know that they are not alone.

While working as test manager for a company that manufactured mass spec units, I managed to short the internal high voltage source to main PC board with spectacular results. The machine itself retailed for $300,000. The PC board, of course, could be replaced so the whole unit was not destroyed, but can you imagine how you would feel if you were a lab tech doing chemical analysis and you zapped it?

The up side is that we corrected the problem, and since it was my job to try and break these guys... well I did my job even though I didn't know I was doing it at the time.

So since I really don't know what the repair would have cost outside the "test" situation, lets just say I zapped a $300,000 piece of equipment.

We have $300,000... do I hear anything higher?
74  Using Arduino / Motors, Mechanics, and Power / Re: Controlling a Peristaltic Filler with the Arduino on: September 01, 2012, 08:13:54 pm

    I am assuming pressing the foot switch just connects pin 1 to pin 2 temporarily.  

No, it should connect the pin1 the logic pin to pin 3 the ground pin. The 24 volts should just power whatever it is that drives the mechanism.

If it just requires a 5 volt signal to toggle the mechanism, then you should be able to connect the Arduino directly to the logic pin 1 with a common ground on pin 3.  Might be wise to see how much current the input pulls when the logic goes high. If it is less than about 30 mv then you can connect directly. it should be way less than that for most solid state things. If it isn't then you need to use a transistor or some other device between the Arduino output and pin 1. The Arduino would be connected to the base of the transistor through a 1 k ohm resistor. If there is a inductive kick ( some sort of relay) down the line from the Arduino, you should also put in a bypass capacitor.
75  Using Arduino / Motors, Mechanics, and Power / Re: Have I stuffed my stepper driver? on: September 01, 2012, 07:51:40 pm
there was a bad smell and I shut it down pretty quickly

By the time you smell it, it is too late. Yeah you smoked something. probably the board. You might check it out with a multimeter, sounds like there is some functionality. See if it draws a lot of current when nothing is happening. That would mean you burned a new current path some where. The driver working a low amps and not at higher amps may mean you partially fried something and now you have a high resistance path to output that limits the current and unbalances the steps after a certain load. Either way, the easiest thing is to just get a new board unless you are into removing board components. 
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