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Design Program for a 8051 Digital Temperature Controller

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dav456

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The circuit uses a
1.LM35 temperature sensor
2.AT89C51 microcontroller
3. 2 CD4511 BCD to HEX
4. 2 7 SEG disp
5. a relay connected to a lamp
6.ADC0804

The LM35 is connected to the ADC.
I want to set a temperature say 40 degrees celcius

The microcontroller will read the temperature from lm 35 and display it in the 7 segment display.

If the temperature is less than the set temperature
the lamp will glow else not.

How do I go about this program.

Does having a capacitor infront of CS pin of ADC0804 ensure it is always 0 instead of connecting it to 8051 and programming it to be 0?
 

Hi,

Some issues:
* Why the pull-up resistors at P0x?
* Why do you use the 7407?
* you should use a 100n X7R capacitor at EACH IC VCC pin with short connection to GND plane.
* your 7805 will becom very hot. You need a heatsink. Or use a transformer with lower secondary voltage.
* Why two transistors to drive a relay?

Klaus
 

KlausST said:
Hi,

Some issues:
* Why the pull-up resistors at P0x?
* Why do you use the 7407?
* you should use a 100n X7R capacitor at EACH IC VCC pin with short connection to GND plane.
* your 7805 will becom very hot. You need a heatsink. Or use a transformer with lower secondary voltage.
* Why two transistors to drive a relay?

Klaus
Click to expand...

I have not used 7407 in real circuit

I read P0 of 8051 is open drain hence we have to use pull up register

I have used heatsink
 

KlausST said:
Why two transistors to drive a relay?
Click to expand...

In addition to Klaus remark, from where comes the voltage V_raw applied to relay bobin ?
If you did that to provide some impedance to 5V, it's ok, otherwise uC will be susceptible to reset.
 

andre_teprom said:
In addition to Klaus remark, from where comes the voltage V_raw applied to relay bobin ?
If you did that to provide some impedance to 5V, it's ok, otherwise uC will be susceptible to reset.
Click to expand...

I dont know if it works with v raw or 2 transistors or not till I simulate the circuit,which is why I need the program.
My first priority is to read the temperature and display it.
 

Hi,

without knowing what V_raw is and without the relay specifications nobody can guarantee the function.
Even the simulation won´t tell you if it works or not.

Do you want us to guess?

Klaus
 

dav456 said:
I dont know if it works with v raw or 2 transistors or not till I simulate the circuit,which is why I need the program. My first priority is to read the temperature and display it.
Click to expand...
So, the additional working circuitry's description you gave is purposeless for the current demand.
Did you make a search on this forum using keyword criteria “8051+LM35+ ADC0804” ? I found many occurrences.
 

andre_teprom said:
So, the additional working circuitry's description you gave is purposeless for the current demand.
Did you make a search on this forum using keyword criteria “8051+LM35+ ADC0804” ?
Click to expand...

I did google a lot but none of them use cd4511 and 2 7 segment

I can fix the transistor part later but what I care more is the port that drives the relay is working or not.

The rest of the circuit is pretty much fixed.
I need the program.

- - - Updated - - -

KlausST said:
Hi,

without knowing what V_raw is and without the relay specifications nobody can guarantee the function.
Even the simulation won´t tell you if it works or not.

Do you want us to guess?

Klaus
Click to expand...

vraw is the voltage before 7805
For now as long as the port that drives the relay is working as per program and the the temperature is properly displayed it is ok.

I can see in the simulation if the port is high or low.
 

Hi,

You know: I = U / R.

I wonder how you say your calculator to divide "the voltage before 7805" by "the resistance of the relay".

Klaus
 

dav456 said:
The rest of the circuit is pretty much fixed.
I need the program
Click to expand...

I can't believe that you have not found any usable code either at Google or at , with which you could start your own project. Please tell me that you're not expecting that someone give you the whole working code for specifications you stated at post #1.
 

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