go_away

Author Topic: Lm335a Temperature Sensor  (Read 1088 times)

0 Members and 1 Guest are viewing this topic.

Offline MastermimeTopic starter

  • Supreme Robot
  • *****
  • Posts: 316
  • Helpful? 5
Lm335a Temperature Sensor
« on: April 14, 2012, 08:13:08 PM »
Hello everyone,

I am using the Lm 335A Temperature Sensor with an Axon II and am transmitting that data back to my computer using Xbee modules.   There are so many schematics to use on this datasheet I just don’t know which one is applicable for my project. 

My original plan was to connect the temperature sensor directly to the Axon II’s ADC pins, but this PDF suggests that is a little more complicated than that.

If you scroll down to page 6 on the PDF, all the schematics are displayed there.  My hypothesis is to use the  ‘Basic Temperature Sensor’ circuit and then connect this to the Axon’s ADC pins.  Could one of you enlighten me on what the correct way of doing this would be?


Thanks

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Lm335a Temperature Sensor
« Reply #1 on: April 15, 2012, 06:19:24 AM »
Hi,

If you scroll down to page 6 on the PDF, all the schematics are displayed there.  My hypothesis is to use the  ‘Basic Temperature Sensor’ circuit and then connect this to the Axon’s ADC pins.  Could one of you enlighten me on what the correct way of doing this would be?
What pdf is that?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline MastermimeTopic starter

  • Supreme Robot
  • *****
  • Posts: 316
  • Helpful? 5
Re: Lm335a Temperature Sensor
« Reply #2 on: April 16, 2012, 11:44:32 AM »
Oh wow I completely forgot to post the pdf.  Sorry about that.  Here it is http://www.ti.com/lit/ds/symlink/lm335a.pdf

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Lm335a Temperature Sensor
« Reply #3 on: April 17, 2012, 09:53:08 PM »
Hi,

There are so many schematics to use on this datasheet I just don’t know which one is applicable for my project. 

My original plan was to connect the temperature sensor directly to the Axon II’s ADC pins, but this PDF suggests that is a little more complicated than that.

If you scroll down to page 6 on the PDF, all the schematics are displayed there.  My hypothesis is to use the  ‘Basic Temperature Sensor’ circuit and then connect this to the Axon’s ADC pins.  Could one of you enlighten me on what the correct way of doing this would be?
You could use the "Basic..." and just calibrate it in software.

The max. range of the chip is -40°C to 100°C (2.3315V-3.7315V calibrated) and you'll likely use it for an even smaller range, like eg. 15..35°C, which equates to a voltage range of 200mV, wasting a lot of range of the A/D-C. If you're OK with that, just use something between 1k and 2.2k (1k5 should give the best results - just enough current and hence minimum self heating).

If you need it to go above 57°C, you need a 5V supply (which the above values are based on as well), as a 3.3V supply will limit the max. to less than 57°C. If it's gonna monitor ambient temperatures where you are, that won't be a problem though, as in such heat, you won't be able to care about robots, temperatures, pretty girls or anything at all ;)

Back to the "Basic..." circuit...
The output can go directly into the A/D-C. Its impedance is under 1 Ohm, so no problem in that. Even so, if you mount it with long leads, twist the wires (around 2 full twists/inch) for common-mode rejection and keep the wires free of actuator wiring, if the signal is noisy.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline MastermimeTopic starter

  • Supreme Robot
  • *****
  • Posts: 316
  • Helpful? 5
Re: Lm335a Temperature Sensor
« Reply #4 on: April 19, 2012, 03:45:03 PM »
Ok thanks.  Consequently, the robot I'm building must be able to work in extreme and harsh conditions.  No Problem there though.  I'll just connect it to the Axon's 5v ADC pins.  Thanks again! :)

 


Get Your Ad Here