Electromagnet - overheating

Discussion in 'General Electronics Chat' started by jake0909, Dec 16, 2015.

  1. jake0909

    Thread Starter New Member

    Dec 16, 2015
    2
    0
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,801
    1,105
    Welcome to AAC!
    It's always a good idea to include a fuse or thermal cut-out, but if the solenoid is rated at 2.5W continuous power (check the datasheet) it will draw ~200mA (not 1.2A), get warm/hot, but should still be safe.
     
    jake0909 likes this.
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    It will only draw as much current as the wire resistance and voltage allow. 12 volts will make 1 amp of current flow through a 12 ohm resistance.
    Voltage divided by resistance is equal to current.
    Your magnet should have a resistance of about 48 to 50 ohms cold and resistance will increase with heat till the stated 200 milli amps of current is all that can flow when supplied with 12 volts.
     
    jake0909 likes this.
  4. jake0909

    Thread Starter New Member

    Dec 16, 2015
    2
    0
    Thank you for your help!
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,145
    3,055
    Check the voltage quickly when it is first connected. An old wall wart (transformer) supply with those ratings is likely unregulated and may be a much higher voltage when not loaded to its labelled current. In this case 15V or more would not surprise me. This could indeed risk overheating your magnet if left connected for an extended time.

    There are many options: Use a 9V AC/DC converter, use a modern (regulated) 12V supply, use your existing converter with a voltage regulator IC such as 7812.
     
  6. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    3,574
    2,543
    What are you using the electromagnet for? Sometimes magnets like that are driven at full capacity at startup, and then a PWM goes in effect in order to reduce current and heating. Another strategies are current limiting, or a simple disconnect timer.
     
    Ronald123 likes this.
Loading...