designing a Solenoid

Discussion in 'General Electronics Chat' started by devalvyas, Nov 22, 2008.

  1. devalvyas

    Thread Starter Active Member

    Nov 11, 2008
    80
    0
    Hi,

    I would like some help in designing a solenoid.

    My application requires a solenoid to push 3kg to distance of 1-2 inches.

    Here are my thaughts on the subject, as i have not really worked on solenoids before.

    Solenoids is small tunnel of coils that produce magnetic field when energised. There is a rod or core inside this tunnel which is pulled or pushed when the solenoid is energized. Now if i connect a strong permenant magnet to one end of the rod such that the permenant magnet is almost in contact or is in contact with solenoid, then if i energize the solenoid, the force generated by the stroke will be higher as compared to simple iron core. or we can say electric power requirement will reduce for same force. is this correct?

    Can i replace the iron rod with a permenant magnet to increase stroke power?

    Now i want stroke of 1-2 inches and the stroke should move a weight of around 3kg.

    The solenoid has to run on 6 volts, that is 4 AA batteries and consume around 200 to 300 mAmps. The dutly cycle will be 25% under normal operation


    1. Can this be designed? Can any one please guide on how to build it?
    2. Practically speaking, What is the max push i can generate by 6 volts battery and 200 to 300 mAmps current?
    2. given the same amount of electrical energy applied, is a solenoid better than dc electric motor for same mechanical output?
    3. Is there some website, worksheet that can help me design the solenoid?
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    #2 ,one or two oz. #3, Given 6V @ 200mA gear reduction motor would be my choice.
     
  3. devalvyas

    Thread Starter Active Member

    Nov 11, 2008
    80
    0
    Even i am looking at dc geared motor, howeve my application backdriving, which is not possible with gear motor, hence i am searching for options?

    Can i make the solenoid longer or with more turns to generate atleast 1 kg push for around 2 inches?
     
  4. devalvyas

    Thread Starter Active Member

    Nov 11, 2008
    80
    0
    i mean my application involves backdriving....
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    I do not understand " backdriving " For 1kg & 1 in @ 6V would take about 20 A.Example: CAT# SOL-58; 4Ω coil @ 24 V,pull force 3.7 lb distance moved not given but plungrr is 3 in. long, body.77 in X 1.82 in. Drain then would be about 6 A.or 144W divided by 6 and the 4 AA would need to deliver 24 A.Ouch!! Also duty 10%. As a guestimate fill a spool 1X2in with 3/8 plunger with enough wire to make .6 Ω. Choose a wire size ,calculate number of turns and layers tofind length;then calc. resistance. if close to .6 try it ,or pick another wire size and start over. Try # 16 first. I think others might give you a more scientific approach. See you in 2 weeks.
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    Using 1 in. dia.,2 in long coilform with thin wall plastic core 3/8 dia;78 ft. of # 19 enamel covered cu. wire,435.6 turns gives coil resistance of .6Ω.If you used 4 Ni/Cd ,C cells it might work. Plunger about 5/16 in.X 3in.with non magnetic extender for the push.[3/32 brass rod threaded in to plunger]. # 19 might be hard to find, then go to # 18,maybe stretch coil length another 1/4 in. A mild steel sleeve [EMT] magnetic return might help. Off to Albuquerque in the AM.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Hmmm. 6v through 0.6Ω will give 10A current. The batteries will explode. :eek: Not good!

    A Bic pen has a barrel diameter of 0.330". If one glued on a couple of cardboard washers spaced 2" apart and wound on 2,005 turns of AWG 30 magnet wire evenly in 11 layers (about 233 feet of wire) the resulting coil would have 24Ω resistance, for 250mA current; right in the middle of our OP's power requirement spec. As far as the pull on the core, I have no clue.

    A stronger magnetic field would be generated by a longer wire. Using AWG 24 magnet wire, 3,385 turns on the same bobbin (935 feet of wire) would also require 250mA current (24Ω). The resulting magnet would be nearly 1.8" in diameter.
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Don't solernoids use AC to generate even more thrust? Something to do with Counter EMF, I think doorbells use the trick. Speaking of which, a Door Bell has several, if it isn't electronic.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, there are solenoids designed for both DC and AC. The DC solenoids have a higher resistance for the same voltage rating as their AC counterparts.

    Solenoid design is rather involved, and I don't have a good understanding of it. Lots of parameters are involved.

    Well, the old style "ding-dong" doorbells from the 50's-80's had a pair of solenoids that ran from a 24vac transformer. The upper solenoid was energized when the front door button was pushed, striking the high "ding" note. When the button was released, the spring-loaded ram retracted, striking the low "dong" note.

    The lower solenoid was activated by pressing the rear door button, causing it's ram to just strike the low "dong" note.

    Since our OP wants to run from batteries with very low power, they'll have to attempt to come up with something themselves. I'm not optimistic about their chances of success, using such a limited power source.
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I wonder if he couldn't convert the DC into an AC signal for better results, something like an H bridge across the solernoid.
     
Loading...