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1  Using Arduino / Sensors / Re: DS18B20 all displaying 32*F on: July 01, 2013, 03:06:23 pm
Quote
saltwater
corrosion of wires contacts pins of the chip, ...?
I've seen zero corrosion anywhere but for the sake of argument, which wire would cause it to throw 32*F? If the 'one wire' is pulled it reads -196*F.

Would lack of power, from a corroded wire, to one or more cause the 32*F reading? I'll play around with the power side of things and see what happens. Also I've replaced the 4.7k resistor with no change.
2  Using Arduino / Sensors / DS18B20 all displaying 32*F on: July 01, 2013, 02:37:25 pm
I'd been running 6 DS18B20's for 2 years reading temps in a saltwater tank and ambient air as well. Originally they were running parasitic, but later set them up powered individually. A couple months ago 1 of them died and started reading -196*F, but I already had redundancy so I hadn't replaced it yet. Today all of the temps read 32*F (0*C). In the past, this has happens every couple of months, I simply reboot it and then it's fine. But today no amount of rebooting, wire jiggling, what-not will fix it. If I pull the "one wire" while it's running they all got to -196*F.

It's been 2 years since I touched the code, and I know all sorts of things have changed, but I have to assume it's a hardware issue. Anyone have thoughts as to what I can look for?
3  Using Arduino / Sensors / Re: PH PROBE atlas-scientific - Arduino 1 - on: August 24, 2011, 08:34:33 am
Any further advice?
4  Using Arduino / Sensors / Re: PH PROBE atlas-scientific - Arduino 1 - on: August 20, 2011, 07:08:30 pm
Quote
Does that mean that it's not seeing probe?

That means that there is nothing received at all!

Chance is that you mixed up the TX and RX line . You could change them and see if bytes arrive....
If they are switched then I get no flashes or red, just a solid green light. And 0's.
5  Using Arduino / Sensors / Re: PH PROBE atlas-scientific - Arduino 1 - on: August 20, 2011, 12:42:08 pm
Quote
But once it's uploaded it does nothing.

Add some sprint statements of let LED13 blink, code might be blocking!

e.g.   Add Serial.println(mySerial.available(), DEC);    in the loop to see bytes are received...  code might be blocking on   if (mySerial.available() > 3)


That gave me a response at least. It spewed 0's, one per line, infinitly.

It looks like the green LED does it's flash and then stays on, but the red flashes more or less continuosly.

Does that mean that it's not seeing probe? It has to see the stamp at least to get the green LED to flash, I assume. What should I next?
6  Using Arduino / Sensors / Re: PH PROBE atlas-scientific - Arduino 1 - on: August 18, 2011, 04:21:07 pm
If I could piggyback on this. I just got my pH stamp today and after wasting plenty of time to find out not to use the marked Tx/Rx pins (0,1) on my Mega1280 I used pins 6,7 (random free pins) to finally get it to upload. But once it's uploaded it does nothing.

Using code from this page:
http://atlas-scientific.com/arduino-test-code.htm

Last time I had an issue like this it was because I was using a Mega1280 with specific pins for SCL and SDA (RTC I'm looking at you) and once it was sorted out everything worked great. I notice that my arduino has Rx1,Tx1, Rx2,Tx2, pins, should I use those? Actually I tried a set of those, 18, 19 I think and had no success after upload as well.

Thoughts?
7  Using Arduino / LEDs and Multiplexing / Re: Fine tuning dimming LEDs with PWM on: July 16, 2011, 09:55:20 pm
I've just read in a fish tank forum how they were able to solve the flash by turning off the power supply before the LEDs are dimmed to "0". I'll give this a try and check back in. Thanks for the help guys.

Bah. After some testing and more reading I've come up with: "That flash? Yeah Meanwells do that..."

Would someone be able to throw together a quick diagram of how I'd need to hook up the relay and resistor? Thanks.
8  Using Arduino / Sensors / Re: Proper MOSFET to power DS18B20 in parasite mode on: July 16, 2011, 12:29:29 pm
Further, potentially anecdotal, evidence as to a power issue is that when I plug the Arduino into the laptop it throws -127C very frequently, where as on the straight power from the wall it only throws the -127 every once in a while...
9  Using Arduino / LEDs and Multiplexing / Re: Fine tuning dimming LEDs with PWM on: July 16, 2011, 11:39:07 am
I've just read in a fish tank forum how they were able to solve the flash by turning off the power supply before the LEDs are dimmed to "0". I'll give this a try and check back in. Thanks for the help guys.
10  Using Arduino / LEDs and Multiplexing / Re: Fine tuning dimming LEDs with PWM on: July 16, 2011, 08:47:19 am
Math is pretty simple:
page 8 in documents for leds, shows charts V-A for different color leds.
The range for blue led V = 2.8 ( I = 0 ) and V = 3.5 ( I = 1000 ma ).
Multiplying this digits by number of leds you plan to connect in series, you will get
minimum and maximum necessary voltage from power supply(driver).
Using this info you can check in data-sheet for driver witch model best fits.

Okay got it finally. took a little assistance from my math teacher wife to show me what I was missing. Thank you Magician.


I still have the other issue that when I shut down the LEDs I also have a solid state relay switch off that controls the drivers. This results in a single full bright flash of the LEDs. Any help pn this?
11  Using Arduino / Sensors / Re: Proper MOSFET to power DS18B20 in parasite mode on: July 14, 2011, 07:39:01 am
Wow lots of activity. My sensors are installed and have cable runs of about 5 feet to 30 feet. If it helps I'm using a ATMEGA1280. Not using parasitic is not really and option I want to explore. The temps I'm monitoring should never be outside of 16C to 26C.

Looks like I'm using v2.0 of the One Wire library and v3.7.0 of the Dallas Temp library.

For the time being I'm not touching the code as it takes too much mental energy and life is quite busy right now.

I'm still interested in "following the directions" and installing a MOSFET, but it kind of looks like I should let you guys argue it out and go from there.
12  Using Arduino / Sensors / Re: Proper MOSFET to power DS18B20 in parasite mode on: July 13, 2011, 07:36:08 pm
Sorry, datasheet here: http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf

I understand the idea of what the paragraph says but not the technicalities of it. In particular the last part:
Quote
The 1-Wire bus must be switched to the strong pullup within 10µs (max) after a Convert T [44h] or Copy Scratchpad [48h] command is issued, and the bus must be held high by the pullup for the duration of the conversion (tCONV) or data transfer (tWR = 10ms). No other activity can take place on the 1-Wire bus while the pullup is enabled


As well needing more power would make sense to me as it's pretty random for each one. As such I ruled out a wiring thing because the likelihood of all of them having wiring issues that only happen at random is pretty unlikely. But the idea of random occasions that it needs more power than is available sounds feasible to me. But then again this stuff just doesn't click for me sometimes...or perhaps more often than sometimes.
13  Using Arduino / Sensors / Proper MOSFET to power DS18B20 in parasite mode on: July 13, 2011, 06:21:35 pm
As I'm not sure if you are responding to me or not and I realized that this is a hardware, not programming, issue I've created a new thread in the appropriate sub forum for my specific issue.

http://arduino.cc/forum/index.php/topic,66452.0.html
14  Using Arduino / Sensors / Proper MOSFET to power DS18B20 in parasite mode on: July 13, 2011, 06:19:06 pm
I have 5 DS18B20s wired in parasite mode which all work. The problem I have is randomly each will read -127C. It seems that I didn't hook it up with enough power which would be taken care of with a MOSFET as indicated by the datasheet. And I don't understand enough to know what it means:

Quote
In parasite power mode, the 1-Wire bus and CPP can provide sufficient current to the DS18B20 for most
operations as long as the specified timing and voltage requirements are met (see the DC Electrical
Characteristics and  AC Electrical Characteristics). However, when the DS18B20 is performing
temperature conversions or copying data from the scratchpad memory to EEPROM, the operating current
can be as high as 1.5mA. This current can cause an unacceptable voltage drop across the weak 1-Wire
pullup resistor and is more current than can be supplied by CPP. To assure that the DS18B20 has sufficient
supply current, it is necessary to provide a strong pullup on the 1-Wire bus whenever temperature
conversions are taking place or data is being copied from the scratchpad to EEPROM. This can be accomplished by using a MOSFET to pull the bus directly to the rail as shown in Figure 4. The 1-Wire
bus must be switched to the strong pullup within 10µs (max) after a Convert T [44h] or Copy Scratchpad
[48h] command is issued, and the bus must be held high by the pullup for the duration of the conversion
(tCONV) or data transfer (tWR = 10ms). No other activity can take place on the 1-Wire bus while the pullup is enabled

To me that is Greek. Any assistance in determining the wiring and hardware would be appreciated. 
15  Using Arduino / Sensors / Proper MOSFET to power DS18B20 in parasite mode on: July 13, 2011, 03:55:02 pm
Check the connections, I've some experience with bad connections and DS18B20 (not in parasite mode) and saw the -127 (too) often. That said could be another cause too.

What is the bit resolution you need, as only for 12 bit there is a need for the 750ms delay.

That said, have you checked - http://www.milesburton.com/Dallas_Temperature_Control_Library - version 3.7.0. There are examples to read the sensors asynchronously so you can do usefull things instead of waiting.


When I had all of the wiring open I could not cause it to -127 by jiggling the wires. It seems that I didn't hook it up with enough power which would be taken care of with a MOSFET as indicated by the datasheet. And I don't understand enough to know what it means from the datasheet.

Quote

In parasite power mode, the 1-Wire bus and CPP can provide sufficient current to the DS18B20 for most
operations as long as the specified timing and voltage requirements are met (see the DC Electrical
Characteristics and  AC Electrical Characteristics). However, when the DS18B20 is performing
temperature conversions or copying data from the scratchpad memory to EEPROM, the operating current
can be as high as 1.5mA. This current can cause an unacceptable voltage drop across the weak 1-Wire
pullup resistor and is more current than can be supplied by CPP. To assure that the DS18B20 has sufficient
supply current, it is necessary to provide a strong pullup on the 1-Wire bus whenever temperature
conversions are taking place or data is being copied from the scratchpad to EEPROM. This can be accomplished by using a MOSFET to pull the bus directly to the rail as shown in Figure 4. The 1-Wire
bus must be switched to the strong pullup within 10µs (max) after a Convert T [44h] or Copy Scratchpad
[48h] command is issued, and the bus must be held high by the pullup for the duration of the conversion
(tCONV) or data transfer (tWR = 10ms). No other activity can take place on the 1-Wire bus while the pullup is enabled

To me that is greek.
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