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 1 Using Arduino / Programming Questions / Re: Function Return on: March 28, 2011, 07:56:49 am Rob,Thanks so much for explaining this. I have it working now. Just so I understand the binary number is actually degrees C / 4 to get the 0.25C resolution? So the part about multiplying that number by 0.25 converts it to degrees C with a precision of 0000.00.So before the multiplication a raw number of say 105 is what the SPI brings back which is 105 quarters of degrees C. So 105 * 0.25 = 26.25CThis is so much fun...ThanksJohn
 2 Using Arduino / Programming Questions / Re: Function Return on: March 28, 2011, 06:14:55 am Is it because the SPI is in BIN the shift bits just pushes the unwanted bits off? I'm not sure I understand how the bit shift divides the number... and how can I get the 0.25C resolution?Thanks for the help.John
 3 Using Arduino / Programming Questions / Function Return on: March 27, 2011, 02:31:22 pm I have a function that I copied from the internet to return the temperature from a MAX6675. I don't understand what the return line is doing to the value obtained from the spi.Code:return((int)(temp_reading >> 5));Is it converting the variable temp_reading to an int? then what does the >> 5 do to the variable temp_reading?ThanksJohn
 4 Using Arduino / Sensors / Re: Thermocouple on: March 27, 2011, 02:20:17 pm Quote from: Graynomad on March 24, 2011, 06:16:51 pmThe A0:1 lines appear to be floating, if so what MUX IO is being selected?______RobBingo Rob! You were correct the A0 and A1 lines can not be left floating. I connected them up and set them to low in my setup loop and walla she works...A big thanks for spotting that.Onward and forward...ThanksJohn
 5 Using Arduino / Sensors / Re: Thermocouple on: March 24, 2011, 07:02:19 pm I've not tried with the thermocouple connected directly to the MAX6675 yet, but that seems like a logical step in trouble shooting.As I understand the data sheet on the ADG609 putting 5v on the EN leg will "connect" the S1A to DA and S1B to DB, putting 5v on combination of A0 and A1 bring the other pairs to DA and DB. Perhaps A0 and A1 "must" be connected and pulled low?I'm really new at this stuff and really appreciate the help.ThanksJohn
 6 Using Arduino / Sensors / Re: Thermocouple on: March 24, 2011, 05:12:07 pm Ok, I understand that using a multiplexer is not the best way. Barring that and the fact that it may not be as accurate as my lab grade thermometer does anyone see why the multiplexer is not passing the thermocouple on to the MAX6675. After further reading of the MAX6675 data sheet if the T- is not connected to ground the only thing this affects is the open thermocouple will not work so a -1 will NOT be returned. So can I assume the MAX6675 "thinks" that there is an open circuit. Is there something in my code that is not switching on the ADG609? Is there some way to see if the ADG609 is being switched on? ThanksJohn
 7 Using Arduino / Sensors / Re: Thermocouple on: March 24, 2011, 10:08:12 am kg4wsv, good catch on the ground but the schematic is wrong. I have the t- connected to ground on the MAX6675. Multiple MAX6675's cost a lot more than one ADG609.If that is correct why is one just like I'm prototyping available on the other side of the earth?http://www.oceancontrols.com.au/KTA-259.htmlI guess I don't have a clue what and "old school" thermocouple is compared to the one I purchased???John