dual controller fan project with attiny45

[joy123]

hello, i never do any programming befoe, last few days i been trying to read as much as i can about programming a pic/atmel with assembly language. go through some flashing led light project but coding for ADC or analog to digital looks over my head . now i am waiting to get a discent enough programmer and development board. as soon as i find something, i have to try to program a PIC16F84A-04/P instead attiny45 (because its very hard to find attiny45 here) for controling this circuit below, is there any guru here to help me out with the c code?

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[Tahmid]

Hi,
You haven't told us what you really want to achieve, but by looking at the circuit, I assume you want to control a DC fan speed according to the temperature. Am I right?

 

[joy123]

thanks for reply, yes , but i want to keep both dc fan turned off, when the temp reach 35c, one fan1 will start, and then if its reach 40c fan2 will kick off too. and the fan will stop when the temp reach 5c less then the set point(35c),

do you know what i mean?

 

[Tahmid]

Hi joy123,
I get what you mean. But you need an ADC to sense the voltage across the thermistor (it's better if you can use LM35 instead) and 16F84A doesn't have ADC (it doesn't have HARDWARE PWM either). You could use a DS18x20 and software PWM or you could go for say, 18F252 or ATmega8. Would make coding MUCH easier.

Hope this helps.
Tahmid.

 

[joy123]

oh ya , i forget about that, ok i think i will find easily 18F252, i will let you know which one is available, then you can help me out with the code................


ps: i found some attiny45 from ebay, it should be here in 2/3 days.

 

[joy123]

ok a quick explanition of the circuit board is
The voltage between +5 VDC and GND (0 VDC) is divided between R1 (fixed resistor) and R2 (thermistor) depending on the temperature. If R1 and R2 have the same resistance they'll both have the same voltage, and the point between them will be halfway between 5 V and 0 V = 2.5 V. If R2 has a higher resistance, then the voltage at that point will be higher. If R2 has a lower resistance, then the voltage at that point will be lower. So, that's the point we want to measure with an analog-to-digital voltage pin of the ATtiny45 (IC1).

The user-adjustable potentiometer (R3) follows the same method to convert its resistance into a voltage. The first pin is connected to 5 V, the third pin is connected to 0 V, and the pin in the middle connects to another analog-to-digital voltage pin on the ATtiny45.

i am using AVR-GCC can you help me with the code please?

 

[Tahmid]

Hi joy,
Do you still need the code for the project?