Please help with code for DS18B20

[malc-c]

In the set up below I used a commercial data logger to record the surface temp of the shelf over a 24 hr period.



Although I had originally posted this in my post above, the forum software said I had more than 4 images ????

[Darrel Taylor]

Malcolm,

Sounds like the perfect job for a PID loop.
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[Acetronics2]

Hi, Malc

Do you understand the "why" of the Parallax document, now ... ???

You'll have to place your Button Key INSIDE the vivarium ( hé,hé ... WITH the snakes !!! ) if you want a true image of your temp.

The graphs you've shown can't be used to finely trim a regulator ... but are a good example.

Temp measurement and moreover probes placing is a real art ... to get a nice temp regulation.

But let's begin by the beginning :

ALL you have to do already is in ZE Book ... with relevant code.

We'll see details later ...

Till then, I'll implement the PID Regulator on my existing " 84 " Thermostat ( not the one shown here, but a nicer one which is pin for pin compatible !! )

Alain

[lew247]

Alain

You were right as always. I hadn't the board configured properly.

I totally forgot about the row of jumpers to set the pins pull-up or pull-down, I had it set wrong.

Thank you

[malc-c]

Hi, Malc

You'll have to place your Button Key INSIDE the vivarium ( hé,hé ... WITH the snakes !!! ) if you want a true image of your temp.

Alain

Agreed,

I've just taken a further reading with the probes 2" from the heater, so its sampling the air temperature. Here's the result (the button logger still on the shelf as shown)



If you ignore the fluctuations in between 10pm and 3am when the snake was out and obviously laying on the sensor, and look at the period 4am to 4pm you'll see it a lot more stable and only has a 0.2C deviation.

DT, could you elaborate on a PID loop.

Alain, could you provide a link to that file... I'm frantically searching for a DS1820 so I can start developing this project, but as my PBP programming is so rusty (and basic) may need you guys to offer some assistance if I get stuck (or should that be when I get stuck )

[malc-c]

DT, could you elaborate on a PID loop.

OK - google was my friend

http://en.wikipedia.org/wiki/PID_controller

[malc-c]

Err.... yeah...

previous_error = 0
integral = 0
start:
error = setpoint - actual_position
integral = integral + (error*dt)
derivative = (error - previous_error)/dt
output = (Kp*error) + (Ki*integral) + (Kd*derivative)
previous_error = error
wait(dt)
goto start

LOL - £34 for a commercial thermostat looks more promising !

[Archangel]

Err.... yeah...



LOL - £34 for a commercial thermostat looks more promising !

What ? That's as clear as mud! I thought they taught you that in primary school.
34 pounds for a thermostat? Must be the VAT ! Damn Globalists, want to federalize the world !
http://www.prothermostats.com/produc...product=100934
$40 US 24.42 GBP

[Darrel Taylor]

OK - google was my friend

http://en.wikipedia.org/wiki/PID_controller

You've got better friends than that.
HenrikOlsson for instance ...

PID-filter routine (2nd try).
http://www.picbasic.co.uk/forum/showthread.php?t=5874

I've used it. It works great.
It's a little tricky to find the correct constants. But trial and error usually works.
Although there is a purposeful method to tune the loop.
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[malc-c]

You've got better friends than that.
HenrikOlsson for instance ...

PID-filter routine (2nd try).
http://www.picbasic.co.uk/forum/showthread.php?t=5874

I've used it. It works great.
It's a little tricky to find the correct constants. But trial and error usually works.
Although there is a purposeful method to tune the loop.
<br>

Sorry Darrel.... it's been a long day......!