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Need help.

e14 Contributor

Hi all.

I need your help. I am building a thermostat that has a fan. The fan starts working when the temprature is too high as well as a red led lights. The problem is that when the red led lights the temprature increases a lot. Why that happens?

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  • 0

    It would help if we could see a schematic to see how you are driving the LED.  Do you have a current-limiting resistor in series with the LED?  If you don't, the transistor driving the LED can get very hot and may fail.  If the transistor is inside a microcontroller, that microcontroller will get hot and may fail.

     

    Typical current-limiting resistor value is 200-1000 Ohms, depending on how bright you want your LED.

  • 0 in reply to johnbeetem

      It may be difficult for you to undrestand. By the way I am new in Arduino and the deadline is near so I am in hurry image

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  • 0 in reply to e14 Contributor

    in addition to Johns comments

     

    The following devices should not be driven directly by the Arduino

     

    Speaker

    Motor

    LEDs without suitable current limiting resistors as John stated but if you want it to be bright then use one of the channels of the LM2003 as stated below

     

    to drive the speaker and the motor you need to employ a transistor driver or another chip to help like an LM2003 which is an 8 channel driver capable of driving the motor and the speaker easily. Speaker may still need a limiting resistor if it a low impedance one (8 - 16 ohms is a lot of current)

     

    a schematic would help too as I can not determine what is connected to what with your picture, only what some of the components are. Also please post the code your testing

     

    what is the model temp sensor

     

    with the direct load you are putting on the controller I am surprised anything is working and if it is it may not for very long.

     

    Show me your schematic and code and I will correct the errors for you that I find

     

    Peter

  • 0 in reply to Robert Peter Oakes

    Peter Oakes wrote:

     

    The following devices should not be driven directly by the Arduino

     

    Speaker

    Motor

    LEDs without suitable current limiting resistors as John stated but if you want it to be bright then use one of the channels of the LM2003 as stated below

     

    to drive the speaker and the motor you need to employ a transistor driver or another chip to help like an LM2003 which is an 8 channel driver capable of driving the motor and the speaker easily. Speaker may still need a limiting resistor if it a low impedance one (8 - 16 ohms is a lot of current)

    Adding to Peter's suggestions, when you drive an inductive load like a motor, speaker, or electro-mechanical relay be sure you include a flyback diode.  They are built into the LM2003 (I think) and most motor drivers, but if you use discrete transistors you'll need to add your own.  If you don't, the driver transistor is likely to get fried.  Here's the Wikipedia page: http://en.wikipedia.org/wiki/Flyback_diode

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  • 0 in reply to Robert Peter Oakes

    Peter Oakes wrote:

     

    The following devices should not be driven directly by the Arduino

     

    Speaker

    Motor

    LEDs without suitable current limiting resistors as John stated but if you want it to be bright then use one of the channels of the LM2003 as stated below

     

    to drive the speaker and the motor you need to employ a transistor driver or another chip to help like an LM2003 which is an 8 channel driver capable of driving the motor and the speaker easily. Speaker may still need a limiting resistor if it a low impedance one (8 - 16 ohms is a lot of current)

    Adding to Peter's suggestions, when you drive an inductive load like a motor, speaker, or electro-mechanical relay be sure you include a flyback diode.  They are built into the LM2003 (I think) and most motor drivers, but if you use discrete transistors you'll need to add your own.  If you don't, the driver transistor is likely to get fried.  Here's the Wikipedia page: http://en.wikipedia.org/wiki/Flyback_diode

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