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Temperature Comparator

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seanhaz:
Hey,
Im an Electrical Engineering student and still in my first year of study so im still pretty new to everything.

I want to build a circuit that compares the temperature of two temperature sensors and gives a variable PWM output to a motor to adjust the speed and also for it to run off solar powered with a small battery backup.

i have attached my circuit diagram i have created, Im using two LM35 temperature sensors giving signals into a ATtiny85 microcontroller in which i will write my program that will give a variable PWM signal depending of the temperature difference of the two sensors.

is there anything you suggest i should change? or anything im missing?

any advice is very welcomed.

Andreas:

--- Quote from: seanhaz on October 03, 2013, 07:43:00 am ---is there anything you suggest i should change? or anything im missing?

any advice is very welcomed.

--- End quote ---

I would place a additional 100nF directly at the ATTiny at the power pins.
The motor return line should go directly to the battery and not across the ATTiny + sensor lines.

How long are the sensor lines? Eventually you will need further decoupling capacitors for the sensors + input low pass filtering for the ADC-inputs.

With best regards

Andreas

dannyf:
1. you need a logic level mosfet;
2. gate resistors too big.
3. solar panel shorted by the battery.
...

this is soething a 555 + two ptc/ntc sensors could do

seanhaz:

--- Quote from: Andreas on October 03, 2013, 07:55:27 am ---I would place a additional 100nF directly at the ATTiny at the power pins.
The motor return line should go directly to the battery and not across the ATTiny + sensor lines.

How long are the sensor lines? Eventually you will need further decoupling capacitors for the sensors + input low pass filtering for the ADC-inputs.

With best regards

Andreas


--- End quote ---

thanks for the reply,

is the extra 100nF cap at the ATtiny to give it a more stable voltage?
and routeing the motor directly to the battery due to interference?

the sensor lines will be 2-3meters

seanhaz:

--- Quote from: dannyf on October 03, 2013, 08:22:02 am ---1. you need a logic level mosfet;
2. gate resistors too big.
3. solar panel shorted by the battery.
...

this is soething a 555 + two ptc/ntc sensors could do

--- End quote ---

thanks for your reply,

I thought the FQP30N06L was a logic level mosfet?
what size resistors do you recommend?

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