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ArcticMyst Security by Avery

small help with a circuit






ndrew2505

ndrew2505

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a friend told me i was supposed to use the 2 offsets(n1 & n2) on the op amp along with along with the vin+&- and the out pin. i suck at schematics so im kinda lost. ive tried building the circuit 4 times and everytime the op amp gets hot so i know im hooking something up wrong just not sure what... :-/
 
lasersbee

lasersbee

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drew said:
a friend told me i was supposed to use the 2 offsets(n1 & n2) on the op amp along with along with the vin+&- and the out pin. i suck at schematics so im kinda lost. ive tried building the circuit 4 times and everytime the op amp gets hot so i know im hooking something up wrong just not sure what... :-/
Click to expand...

There is only one offset pin on the LM741 OP Amp... it is pin #1 and you DO NOT need it for this
circuit.

Which exact OP Amp part number are you using... and do you have a copy of the data sheet so you
know the pinouts... :-?

Here is a data sheet... http://www.fairchildsemi.com/ds/LM/LM741.pdf

I think you are referring to the Inverting Input (IN1) Pin #2 of the 8 pin IC and the Non Inverting
Input (IN2) Pin #3 of the IC.

All you need to do is follow the schematic like a road map (Point A to Point B)
The only pins of the OP Amp you need to connect are:

Pin #2 goes to the junction of the 100k Pot and the Thermistor

Pin #3 goes to the junction of the two 10K and one 270K Resistors

Pin#6 goes to the Junction of the 270K and 4K7 Resistor

Pin #7 goes to the Positive Supply

Pin #4 goes to the Ground (the Negative Supply)

No other connections to the OP Amp are required for this circuit...

Since your OP Amp got hot... there is a good chance that it is fried..
Use a new part and try it again... ;) The circuit is simple enough that
you should have no problems if you just follow the road map (schematic).

Jerry
 
lasersbee

lasersbee

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drew said:
http://focus.ti.com/lit/ds/symlink/ua741.pdf

this is the opamp im using. i guess i was told wrong about something.. :-? i also think the opamp was getting hot b/c it was hooked up wrong....
Click to expand...

Are you using the 14 pin IC or the 8 pin IC... :-?

The pin numbers are NOT the same for the two types... one is a dual Op Amp and
the other is a single Op Amp...
The Pin Numbers I quoted above are for the 8 Pin OP Amp IC.
 
ndrew2505

ndrew2505

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oops my bad ;D im using the 8pin ic. ::)

ill try rebuilding it after work tonight but ive got to leave in a few so i dont have time. i suck at reading schematics.... ::)
 
lasersbee

lasersbee

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Just take it slow a methodically and you'll get it... it's really not that
difficult... ;)

Jerry
 
ndrew2505

ndrew2505

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i know its not that difficult but i dont know how to read some schematic details and was told to use the wrong pins. thanks for the clarification jerry. ;)
 
lasersbee

lasersbee

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drew said:
i know its not that difficult but i dont know how to read some schematic details and was told to use the wrong pins. thanks for the clarification jerry. ;)
Click to expand...

If you need an explanation of a part or the way it is connected on this circuit... you can PM me.. ;)
 
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