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I am trying to put three solenoids in parallel so that I can connect the shafts together and get more power from them on switching them on at the same time. I see this diagram for one solenoid.

Can someone help me decide what additional components do I need to add two more in parallel to the existing one. I have a 12V, 3A power supply, three solenoids of 12V and 1A each.

many thanks, Marc

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  • \$\begingroup\$ Welcome to EE.SE. You haven't linked to a diagram - you've linked to a whole Instructables article. Post the schematic here so that nobody has to trawl through the link. "AMp" should be either "amp" (lowercase if spelled out) or "A" (uppercase if abbreviated) as per SI standard. \$\endgroup\$
    – Transistor
    Jul 1, 2017 at 14:10
  • \$\begingroup\$ cdn.instructables.com/FGU/MHKE/I4CMQFA5/… \$\endgroup\$
    – marc Katz
    Jul 1, 2017 at 14:15
  • \$\begingroup\$ Make it easy for those from whom you seek help. There's a picture button in the editor. It takes links and will embed the picture in your post. (If you haven't enough rep it may appear as a link but someone else will fix it.) Fix the typos while you're at it. \$\endgroup\$
    – Transistor
    Jul 1, 2017 at 14:19
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    \$\begingroup\$ That's fine, marc, although you will notice that you haven't got any answers yet and that may give you a clue. Comments don't interfere with anyone's ability to post comments or answers. Bye. \$\endgroup\$
    – Transistor
    Jul 1, 2017 at 14:46
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    \$\begingroup\$ @marcKatz links go dead. Also you are here requesting help so could you help us help you. what part EXACTLY are you interested in \$\endgroup\$
    – user16222
    Jul 1, 2017 at 14:57

2 Answers 2

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@marc_Katz The best bet is not use TIP120 Darlingtons which have a spec of:

Vce(sat)=2V @Ic=3A or an equivalent Rce of 2V/3A= 2/3 Ω .

Instead use a logic level Nch MOSFET that runs off Vgs=5V ,which is at least 3x the gate threshold voltage , and has >= 8x the current rating and an RdsOn of << 100mOhm with a reverse body diode for clamping the Back EMF.

This gives many SMT solutions, but if you prefer leaded parts consider https://www.digikey.com/product-detail/en/infineon-technologies/IRL2703PBF/IRL2703PBF-ND/811700 ($1) which is a 40 mΩ, 24A TO-220 part.

  • At 3A it will dissipate < 0.25W
    • and use twisted pairs to reduce EMI when switching off the solenoids with good decoupling caps at 12V source.

As warned correctly by @Janka this is more of a mechanical problem with force, mass and mobility with tradeoffs for acceleration, force and stroke length depending on mass and momentum of inertia and final kinetic energy. You might have to re-think the problem in these terms then define the power and energy needed to do the job as well as humans with pull tendons and muscles. So a gear motor might be a compromise with current sensing and/or rotation sensing for end stop with more complex control functions, or a bigger brute force solenoid that requires holding power.

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I strongly disadvise to parallel solenoids for mechanical reasons. They never pull exactly the same so a parallel setup is prone to tilting and jamming. If the force isn't high enough, think of a bigger solenoid or a motor.

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  • \$\begingroup\$ It would demand parallel guide rods to prevent tilt with parallel ends with large sleeves or roller bearings. \$\endgroup\$ Jul 1, 2017 at 17:05

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