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Anyone used the LM35 analog sensors? They're only A$1.85ea at modtronix. Is 0.8 of a degree accuracy (at the extremes (0degC and 100degC)) good enough? I like the idea of being able to chain the DS1820s on a single bus, but I don't want to order three more and get three more duds.

edit: forgot to close a bracket :rolleyes:
 
They might not be duds Bonj. They are pretty fussy about the bus timings.

Did you try wiring up the circuit that allows you to run them from the serial port on your PC?
 
They might not be duds Bonj. They are pretty fussy about the bus timings.

Did you try wiring up the circuit that allows you to run them from the serial port on your PC?
I haven't yet, as I don't have a serial port within easy access. I will try it though, just to make sure. I used the OneWire library available for the arduino development environment, which many have reported success with on identical hardware (the arduino diecimila is an AVR ATmega168 @ 16MHz), so while possible, it would be unlikely that the timing worked for all those others but not for mine. They won't even respond to a reset, which is supposed to pull the pin LOW. The reset code is pretty simple:
Code:
//

// Perform the onewire reset function.  We will wait up to 250uS for

// the bus to come high, if it doesn't then it is broken or shorted

// and we return a 0;

//

// Returns 1 if a device asserted a presence pulse, 0 otherwise.

//

uint8_t OneWire::reset() {

	uint8_t r;

	uint8_t retries = 125;



	// wait until the wire is high... just in case

	pinMode(pin,INPUT);

	do {

		if ( retries-- == 0) return 0;

		delayMicroseconds(2);

	} while( !digitalRead( pin));



	digitalWrite(pin,0);   // pull low for 500uS

	pinMode(pin,OUTPUT);

	delayMicroseconds(500);

	pinMode(pin,INPUT);

	delayMicroseconds(65);

	r = !digitalRead(pin);

	delayMicroseconds(490);

	return r;

}

I do suppose after reading that code again, that I should ensure that it's not just timing out on the retry loop, but either way, they were wired up correctly and tried on both powered and parasite configuration, with no response. There's definitely something wrong.
 
Have you got a CRO there Bonj so you can have a quick look at the waveform?

What value pull up resistor do you have?
 
I don't have one, but I will borrow my brother inlaw's to check them out.

I can't remember off hand, and am too lazy to check the datasheet, but I think it was a 4.7K.
 
Anyone used the LM35 analog sensors? They're only A$1.85ea at modtronix. Is 0.8 of a degree accuracy (at the extremes (0degC and 100degC)) good enough? I like the idea of being able to chain the DS1820s on a single bus, but I don't want to order three more and get three more duds.

edit: forgot to close a bracket :rolleyes:

I used them in my old fridge controller (since moved to a mashmaster since my construction is so dodgy it eventually fell to pieces) They work well. If your reading them with a computer via ADC no problem. If you are using them in an analogue circuit you will probably want to use the offset pin to make them read correctly in degress kelvin. The biggest problem I had was the supply circuit for the LM35 shared a +5V rail with the supply for the optoisolator driving my triac. When the fridge turned on there was enough voltage drop on the supply rail to alter the reading from the optoisolator. I tried buffering it with a bigger capacitor but it was still a problem. So if you are going to use one, overengineer the supply rails for the LM35 and comparators.

BTW I wouldn't run the DS18S20s on parasitic power for similar reasons. Reading the spec sheet they loose accuracy at higher temperatures (above 80C IIRC) when on parasitic power because the conversion takes longer and they don't have enough juice available to keep functioning through the whole cycle. Having said that I haven't played with my DS18S20s yet so take that with a grain of salt.
 
does anyone know what sensor is inside the mash master probe here

could make life easy!
 
does anyone know what sensor is inside the mash master probe here

could make life easy!

An analogue NTC sensor by the looks of it (negative temp coefficient resitor). Not sure what the specifics are though (you could easily work out it's resistance @20deg though with a multimeter).

I'm sure Frank will give you more info than this.
 
Anyone used the LM35 analog sensors? They're only A$1.85ea at modtronix. Is 0.8 of a degree accuracy (at the extremes (0degC and 100degC)) good enough? I like the idea of being able to chain the DS1820s on a single bus, but I don't want to order three more and get three more duds.

I use LM35's in my HERMS - they're reliable and accurate. I've also played around with 1820's with no issues. Unless you can scope the data line to ensure that your firmware isn't the issue, don't assume that the sensor is at fault. <_< Hang on. What sort of ESD countermeasures do you follow? That would explain why they're not working for you.

Regarding the accuracy of the LM35, I'm reminded of a quote I read elsewhere: A man with a thermometer knows the temperature. A man with two thermometers is never sure. A roundabout way of saying don't worry about the 0.8C accuracy as "ordinary" thermometers don't come with an accuracy spec - you can only hope they're as accurate as the LM35.
 
I use LM35's in my HERMS - they're reliable and accurate. I've also played around with 1820's with no issues. Unless you can scope the data line to ensure that your firmware isn't the issue, don't assume that the sensor is at fault. <_< Hang on. What sort of ESD countermeasures do you follow? That would explain why they're not working for you.

Regarding the accuracy of the LM35, I'm reminded of a quote I read elsewhere: A man with a thermometer knows the temperature. A man with two thermometers is never sure. A roundabout way of saying don't worry about the 0.8C accuracy as "ordinary" thermometers don't come with an accuracy spec - you can only hope they're as accurate as the LM35.

Now that you mention the ESD countermeasures, I have a feeling that the laptop doesn't have a good enough ground for me to ground myself properly. I guess I could have staticed them to death.

If I used the LM35, they'd be connected to the analog pins on the atmega168.
 
The thing about ESD is that you actually don't have to come into contact with the electronics/chip; you can damage it without touching it. Some of the more sensitive RF stuff that I've been involved with could easily be fried just by coming within about 1m without being properly grounded. The best solution would be to get a proper ESD mat, but simply running a wire from your house outlet's ground to your wrist helps. Also try to clear your workspace of paper. Paper is very, very good at holding a charge which is very bad from an ESD point of view.

Regarding running the LM35 into an ATmega, that's essentially what I do (sort of). I use the Microchip PIC family myself. To get a better range from the A/D converter without adding an amp, consider using an external voltage reference instead of the processor's internal Vdd reference. The general idea is that you get a larger A/D change (number) per degree celcius change when you use a reference that's smaller than the 3.3V or 5V power supply of your processor. This leads to a more accurate temperature reading. The only thing to watch for is that some built-in A/Ds actually have a minimum external Vref without incurring an accuracy hit. For most 5V PICs this is about 3V - you'd have to look into whether this is an issue with the Atmel processors.
 
Alright.... some idiot apparently used a 4.7ohm pullup resistor, when they should have used a 4.7Kohm. Needless to say, that person will not be named, so as to avoid public humiliation. :ph34r: All 3 sensors are now returning data.
 
nice work bonj!


still looking which kit ot get myself a work mate just got the nano which as just been released!

this one looks the goods and cheap as! $28.00

freeduino6.jpg

Rob.

i'm thinkin we start a new thread bonj for all this Arduion Stuff and give poor zizzles thread a break!

i can see a few ppl getting on board with this stuff in the future seeing as it's getting easier and more accessible!
 
Just checked it out Zizzle.
That looks like an awesome little unit with immense potential.
I couldn't see a price on it though.
What is the damage ?

If there was one more piece of tin I'd like to see incorporated though, it would be a wireless module.

Doc
 
Ethernet...


Hmmm...

You could put a brew on ANYWHERE!!!
 
That looks awesome, Zizzle!

I want one :D
 
Help me out here brothers.
I'm from the other side of the planet from hardcore computer guys like you.
Still, I like the degree of difficulty of automating at least some of my brewery.
So, what would be the best 'platform' for me?
I'm happy to devote an old laptop to this app if it came to it.
Arduino? FriendlyArm? Embedded control concepts BCS-460, Picax. What the F are these actually - I'm not sure if these are of the same category.
I need an orientation to this, can ahyone help with an 'English' reference, or at least get me started with a quick explanation.
Cheers.
 
Hi Yorg,

not sure about all the items you mentioned, but mostly they would be different platforms for doing the same thing. Arduino and picaxe are both microprocessor platforms designed for easy programming with good help forums and the like. Basically you start with a chip and then have to figure out all the bits to add on to make it do what you want. You can get industrial strength controllers that will cost an arm and leg but probably be easier to build in terms of the physical interfacing.

I've been coding with a picaxe for a long time and mostly it does what I want it to do. It has some limitations that I find annoying but it is very cheap and easy to use. The arduino is more powerful than the picaxe in most things.

Programming an automated system is a huge undertaking. After doing this for a long time I've conceded that the BrewTroller guys have got a pretty special thing happening which is why I've got one arriving this week.

That frees up my picaxe stuff for making smart add ons, like a hop dropper.

The thing that Zizzle was showcasing is effectively a standalone computer in its own right. You could replace your laptop idea with one of those.

cheers, Arnie
 

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