cheap and simple way to measure temperature

[Heckler]

I am designing a simple PIC electronic POV (persistance of vision) project for the Boy Scout "Electronics" merit badge.

I would also like to include the ability to measure and display temperature. The "display" part is no problem as it will use a POV matrix.

It is the "Sensor" part I need help with. I am considering the DS1820 One Wire sensor, but would love to hear from this group's vast bank of experience. Low cost then simplicity is importaint.

Thanks in advance.

Dwight

[mackrackit]

I like the LM34. It comes in C or F.
Here is an example
http://rentron.com/PicBasic/LM34.htm

[malc-c]

My current project used 4 x DS18B20's

http://www.picbasic.co.uk/forum/showthread.php?t=12712

All you need in addition to the DS18B20 itself is a 4.7K resistor and obviously some means of displaying the temperature it reads - either an LCD display or serial to PC and use Hyperterminal. If you chose the LCD screen, then estimated cost would be less than £25 for the sensor, resistor,LCD, case and (depending on the PIC) the PIC too.

[Acetronics2]

I am designing a simple PIC electronic POV (persistance of vision) project for the Boy Scout "Electronics" merit badge.

I would also like to include the ability to measure and display temperature. The "display" part is no problem as it will use a POV matrix.

It is the "Sensor" part I need help with. I am considering the DS1820 One Wire sensor, but would love to hear from this group's vast bank of experience. Low cost then simplicity is importaint.

Thanks in advance.

Dwight

Hi Dwight

Could you tell us the temp range and precision + resolution you look for ???
Also if you have an ADC aboard your PIC.

Sensor selection will be greatly simplified ...

BTW ... using a OneWire device with some POV Display could be really interesting ... but, it's just me ...

Alain

[Heckler]

I am just looking for ~2 degrees F accuracy. I just want to measure ambient temp. in the range of say 0 to 100 F.

Here is a link to the base kit that I am trying to modify. http://www.chinchillasoft.com/Projects.aspx

This kit is not my design. But I wanted to add the temp sensor to make it more interesting and useful for the kids.

Is it true that the DS1820 does not also require the PIC to have an external precision voltage reference?

It appears that the LM34 does require the external voltage reference. Is that true?

This is a pretty neat kit that shows off the CNC router software on his site also. He uses it to route the PCB instead of etching the board. The kit is only $10 US and that is in the price range that kids can afford for the merit badge. If I could add the temp sensor for say $2 more then I think that would be a neat addition.

Thanks all
Dwight

[mackrackit]

VDD can be used as a reference for the LM34.

[Heckler]

hey Mack,

But if VDD is a 3 volt lithium coin cell whose voltage decreases over time, will that make the temperature also become less accurate over time?

Although, even if that is the case, that may be an acceptable amount of drift for this type of project.

Thanks I'll have to break out the breadboard (DANG!... Now the fun starts)

Still open to suggestions, though.
Price is really the main factor for my needs.

Dwight

[mackrackit]

I wonder how long a project like yours willrun with a coin battery?
Will the coin also be running the motor?

[ScaleRobotics]

Certainly not the cheapest, nor the most simple, but you can pick one up from Future Electronics for just under $10.00. The cool part about this one, is that you could have your POV clock sense a person in front of it, and have it do different things after sensing body heat, like saving your battery life.

http://melexis.com/Sensor_ICs_Infrar...O-can_685.aspx