Solenoids control using microcontroller?

Discussion in 'General Electronics Chat' started by cheesemunger, Jan 25, 2009.

  1. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    I am getting this solenoid:

    http://www.mandeno.co.nz/users/show_item.php?q=6,20,-1,-1,-1,14,74,456,all&key_word=

    ,but not from there.

    I have been told it has a resistance of 35 Ohms. I can run it off 6, 12 or 24 V but I would prefer to run it off 24V. So the Amps it will draw is:

    V=IR
    I=V/R

    V=24 V
    R=35 Ohms

    I=~0.686A

    So I've got that all worked out. I'm just not exactly sure of the schematics or part numbers for the parts? Could any of you help me out?
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Where is the schematic?
     
  3. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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  4. mik3

    Senior Member

    Feb 4, 2008
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    The BD679 says it is NPN but on their datasheet they show a PNP transistor!
    Use the TIP102 for sure. Check if it gets hot as to use a heatsink.
     
  5. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    I've looked around some more and seen that the BD675 is NPN. It must have been a mix up on that datasheet. I think I already have some BD675 so I'll try those.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    If you have then use them ;)
     
  7. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    Does it matter what diode I use?
     
  8. mik3

    Senior Member

    Feb 4, 2008
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    The diode should be a fast diode but a normal diode will work too if you won't switch the coil very fast on/off. I recommend you to use two diodes in parallel in case the one fails.
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    I have had luck with improved de-energize response times by introducing a zener-diode in series with the standard diode. The zener permits the fly-back voltage to be clamped at a level that will permits the magnetic field in the coil to collapse faster than it would do with only the voltage of a forward biased diode. I'll try to locate the application note that recommended this approach and post it in this thread.

    hgmjr
     
  10. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,575
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    Cheesemunger,

    Did you purchase the solenoid in the link? If so, it's a 6VDC coil and will burn up with 24VDC.

    These are for other solenoids.

    Just checking. :confused:

    ken
     
  11. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    How fast is fast?
     
  12. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    OH, I am not getting it from there, I'm getting from eBay. Now I look at it , its a 12 V one. So I'll have to run it off 12 Volts. This affects the amps, but does this affect any parts I need to get?
     
  13. mik3

    Senior Member

    Feb 4, 2008
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    No, you can use the same transistor.
     
  14. hgmjr

    Moderator

    Jan 28, 2005
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    Here is a link on a short article that presents the effects of different transient suppression techniques.

    hgmjr
     
  15. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    So, this article tells me that I should use a Zener and diode in series with each other but do I really need to? Can I use two diodes in parallel like suggested earlier? I don't want to have to get more parts than I need to...:p
     
  16. hgmjr

    Moderator

    Jan 28, 2005
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    The configuration I was suggesting was the zener diode in series with a standard diode. If on and off switching times for the relay are not critical then single diode or the parallel diode approach is a tried and true solution.

    hgmjr
     
  17. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    If I want the solenoid to fire about once every seconds, does that count as critical?
     
  18. hgmjr

    Moderator

    Jan 28, 2005
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    A single diode is probably a good starting point for your application.

    Is your application going to result in the constant operation of the relay in which it cycles open and closed once every second?

    hgmjr
     
  19. cheesemunger

    Thread Starter Active Member

    Jan 25, 2009
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    Mmmm, lets consider this. Ok, it will do 1 every second for 20 seconds then have about a 10 second break then back to start. It should do this for about 20 mins.
     
  20. hgmjr

    Moderator

    Jan 28, 2005
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    If you plan on using the relay over many thousands of operations then you may want to consider using a suitably rated solid-state relay.

    hgmjr
     
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