After searching through the forums i can see this is a common problem - but i cant seem to work out what i need to buy to resolve my issue. I have a Velleman USB 8005 board which has an onboard ADC (8 bit) which takes 0-5v
Ive interfaced an LM35, but due to the low outputs i cant get the results i need ( im measuring temps circa 40-60 degrees celsuis ) - im only getting circa .4 to .8 volts for my temps so im unable to get any meaningful results from the ADC.
I see that i can use a 2 resitors across + and ground and take a reference of 2.5v which may increase the output scale by 2.
I also see that i can use an Op-Amp and scale the output from the LM35 by a factor of 5 which would give me the resolution required by both my application and the ADC.
My (rather long winded) question is - what op-amp and components would i need to buy to fabricate a 0-5v op-amp.
The LM35 and the ADC are all being fed from a 5v supply.
as you can tell, very new to all of this and still trying to get good electronics selection purchased to avoid the frequent trips to maplins.
+9Cdef is fine, im more interested in the 30-85 degrees range, but will have another sensor for monitor outside airtemp and was hopging to use the same op-amp circuit on the other LM35.
For now though, +9 is absolutely fine as my typical readings with the multimeter have been no lower than 29CDeg.
+9Cdef is fine, im more interested in the 30-85 degrees range, but will have another sensor for monitor outside airtemp and was hopging to use the same op-amp circuit on the other LM35.
For now though, +9 is absolutely fine as my typical readings with the multimeter have been no lower than 29CDeg.
Could you clarify what the 5V1Z symbol is , and also the 10K0 with the line through it please? Im so new to all this that i dont want to get anything wrong as it takes days for the components to arive in the post!
Consider that you powered the OPA from a 12V supply, under fault conditions the OPA could drive the input of the ADC upto about +12V. Although the inputs to the PIC are protected, IMO its not a good idea to connect a 12V low impedance source to the ADC input.
The series resistor and 5V1Z, clamp any excessive output to about 5V.
The 10K with a line thru it is a variable resistor, its purpose is to set the gain of the OPA.
In this way you set a +5V output for the 85Cdeg point, OK.?
hey ppl..can you please provide me the circuit diagram for LM35 and then amplifying it using LM358... the circuit that i am building in which LM35 gets really hot