Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Temperature detector design

Status
Not open for further replies.

bahti

Newbie level 1
Joined
May 5, 2011
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,289
Hello,

As a school project i am supposed to desing a circuit that has three leds, one will light when it is lower than 20*c, one between 20 and 30 , and one when higher than 30*c. I can use the device AD22100. it has an output voltage equation like :
VOUT = (V+ / 5 V) × [1.375 V +(22.5 mV/°C) × TA]
where v+ is typically 5v and ta is the temperature.
calculations show that 20*c outputs 1.8v and 30*c outputs 2.1v. I can not find a way to detect this voltage intervals.
Do you have any ideas on how to achieve this?. We are allowed to use any components- diodes, zener diodes, ttl gates, mosfets etc.
Thanks,
 

BradtheRad

Super Moderator
Staff member
Joined
Apr 1, 2011
Messages
13,972
Helped
2,785
Reputation
5,568
Reaction score
2,691
Trophy points
1,393
Location
Minneapolis, Minnesota, USA
Activity points
104,221
Strange. The datasheet states the device can only drive small loads, 1 to 2 mA.

When output reaches, say 1.7 V, this can drive a red led.
But without a resistor in series it will hold the output at 1.7 V. Did the professor say you can use resistors?

Are all led's allowed to be lit at the same time?
If so then you might find another led that will light at 2.1 V. Different voltage ranges apply to different color led's.

If you're very meticulous, you can devise a resistor network that will divide down a target voltage so that it just starts to bias an led. You adjust the divider to the led turn-on voltage.

============

Oh, you ARE allowed to use components.

The easy way is to use an op amp as a voltage level detector. You may need two or 3 of them.
 
Last edited:

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top