OpAmp Help

Thread Starter

Roiw

Joined Nov 22, 2012
12
Hi guys!

I have another simple project that I need help :)

But for this one I need to make it real. ( I need to create the board and stuff)

And I dont know which components to pick. :confused:


I will post here the schematics of the circuit


The Circuit

It's a simple circuit that need to turn on a red light if the temperature of the enviroment is below 10ºC or above 30ºC and a green one if between those values.

BUT I MUST use a Thermistor :( I'm not allowed to use a LM35 for example.

And to make things worse the only ones I have avaliable are 20Ω ones ( But I have 10 of them, so I can at least make a 200Ω Thermistor)

Here is a pic of the circuit I designed and it works:




The VCC on the top OpAmp is +5 and -5

And in the bottom one is 0 and -10v

So, my question is:

WHICH OPAMPS CAN I USE ?

I need a name like LM741.

Thanks a lot guys! :)

EDIT: Forgot to mention! The top left resistor is in fact the Thermistor! ( The top horizontal one)
 

Thread Starter

Roiw

Joined Nov 22, 2012
12
Do you know if I can put (VCC+ = 0) and ( VCC- = -10) on a TL081?

Thanks


Edit: I mean OFFSET N1 = 0 and OFFSET N2 = -10
 

Thread Starter

Roiw

Joined Nov 22, 2012
12
Sorry for that. I'm talking about the VCC+ and VCC- on the op amps.

There is a schematic in the datasheet you gave me and they are referenced as OFFSET N1 and OFFSET N2 ( page 3 ) thats why I said that, maybe offset means something different, sorry for that I'm still learning.

Thanks
 

Thread Starter

Roiw

Joined Nov 22, 2012
12
What's happening is :

Voltage output OPAMP1 -> 5, -5

Voltage output OPAMP2 -> 0, -10

So when my temperature is less than 10ºC OPAMP1 saturates in 5V and OPAMP2 in 0v D1 is turned on

When I'm between 10 and 30ºC my OPAMP1 saturates on -5 and OPAMP2 keeps on 0v
so D1 is off and D2 is on

When I'm above 30 OPAMP1 saturates on -5 and OPAMP2 on -10
so D1 is on and D2 is off

And we get the desired output :D
 
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