"Thermostat using ic741"-circuit explaination please? - Page 2 - Electronic Circuits Projects Diagrams Free

ace.neerav · 26th April 2008, 07:17 AM

i still dont understand the feedback concept?

ace.neerav · 26th April 2008, 07:34 AM

OMG! there is a huge confusion. when does the opamp turn on? when the temperature rises or when the temperature falls?

ericgibbs · 26th April 2008, 07:38 AM

Quote:

Originally Posted by ace.neerav

OMG! there is a huge confusion. when does the opamp turn on? when the temperature rises or when the temperature falls?

hi ace,
I have already previously explained in detail and included a drawing which answers these questions.

May I ask are you studying electronics or is this just to explain the circuit diagram you posted.?

Are you planning to build this circuit.?

ace.neerav · 26th April 2008, 08:51 AM

hi. i am in the nd of second year of electronics and telecommunication engineering. i asked the above question because in our project (which we have already got made from some one and which now only requires to be explained to our professors) when we touch the thermistor the LED would glow. and that would happend only if the opamp o/p tunred high when the the voltage drop accross the thermistor increases and that would also mean that the thermistor has +temp coefficent.

if ur talking about the feed back then as i have not yet come up to the topic of opamp in my self study i m not quite sure what hysterisis is and how the f/b works

ericgibbs · 26th April 2008, 09:05 AM

Quote:

Originally Posted by ace.neerav

(which we have already got made from some one and which now only requires to be explained to our professors)
when we touch the thermistor the LED would glow.
Your circuit does not show an LED???

and that would happend only if the opamp o/p tunred high when the the

voltage drop accross the thermistor increases and that would also mean that the thermistor has +temp coefficent.
Your circuit is showing a NTC thermistor, reducing resistance with increase inTempr

if ur talking about the feed back then as i have not yet come up to the topic of opamp in my self study
There are basically two types of feedback:
negative, this is where a portion of the output signal is fed back to the input in antiphase to the input.

positive this is where a portion of the output signal is fed back to the input in phase to the input.

i m not quite sure what hysterisis is
I would suggest as a starting point that you look [Google] for hysteresis.
Look at magnetic hysteresis also schmitt inputs.
and how the f/b works

hi,
Google for the topics and then come back and ask specific questions.

**Nigel Goodwin** · 26th April 2008, 09:50 AM

This is really a VERY simple circuit, the sort of thing you do in school aged about 13 years old (although they probably don't understand how it works).

As with any circuit, it's all about understanding the basics, surely that's what you've been learning the last two years?.

ace.neerav · 26th April 2008, 01:05 PM

we have not yet been introduced to what a relay is as yet and as for the opamp, it the the final chapter of the subject so havent reached there yet.

ace.neerav · 28th April 2008, 02:43 PM

hello all. i just want to thank u all for ur help. the project explaination was a success! i scored 5 outta 5 in it. thanks to u guys for explaining me the concept.

ericgibbs · 28th April 2008, 02:52 PM

Quote:

Originally Posted by ace.neerav

hello all. i just want to thank u all for ur help. the project explaination was a success! i scored 5 outta 5 in it. thanks to u guys for explaining me the concept.

hi ace,
Is the cheque in the post.?

strongerman · 29th April 2008, 10:41 AM

Hi, i want to construct a circuit which could be used in offices and other security type of Buildings using a C-program or c++ to interface with an electronic circuit can anyone help me with this

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26th April 2008, 07:17 AM	(permalink)
ace.neerav	i still dont understand the feedback concept?

26th April 2008, 07:34 AM	(permalink)
ace.neerav	OMG! there is a huge confusion. when does the opamp turn on? when the temperature rises or when the temperature falls?

26th April 2008, 08:51 AM	(permalink)
ace.neerav	hi. i am in the nd of second year of electronics and telecommunication engineering. i asked the above question because in our project (which we have already got made from some one and which now only requires to be explained to our professors) when we touch the thermistor the LED would glow. and that would happend only if the opamp o/p tunred high when the the voltage drop accross the thermistor increases and that would also mean that the thermistor has +temp coefficent. if ur talking about the feed back then as i have not yet come up to the topic of opamp in my self study i m not quite sure what hysterisis is and how the f/b works

26th April 2008, 09:50 AM	(permalink)
Nigel Goodwin	This is really a VERY simple circuit, the sort of thing you do in school aged about 13 years old (although they probably don't understand how it works). As with any circuit, it's all about understanding the basics, surely that's what you've been learning the last two years?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

26th April 2008, 01:05 PM	(permalink)
ace.neerav	we have not yet been introduced to what a relay is as yet and as for the opamp, it the the final chapter of the subject so havent reached there yet.

28th April 2008, 02:43 PM	(permalink)
ace.neerav	hello all. i just want to thank u all for ur help. the project explaination was a success! i scored 5 outta 5 in it. thanks to u guys for explaining me the concept.

29th April 2008, 10:41 AM	(permalink)
strongerman	Construction of access control system using c-program Hi, i want to construct a circuit which could be used in offices and other security type of Buildings using a C-program or c++ to interface with an electronic circuit can anyone help me with this