Magnetic Latch Valve

Please provide more details. Information like how much movement (distance) will be required and what level of force is required? How is this plunger arranged with respect to the rest of the "latch"? How much free space is available.

Can the coil weigh 100 Kg? How will it fit? If you want a good answer, you will need to provide the physical constraints.

hi thanks for the reply this is a solenoid which needs linear movement. the stroke is at 5mm the voltage should be at 3v ; ll ; ; ll ; ; ll ; ;========; ll / \ the valve is mounted in the condition as shown the plunger face is flat and the head conical. the plunger is used to close an opening which has a fluid flowing at 1.5 bars to calculate the force...the valve needs to close a opening which is 6mm dia

after a thorough study, we have arrived at the following value voltage -- 3v watts-----0.75 R---------12 ohms I---------0.25amps the stroke of the plunger us at 4mm the force required to close the orifice is 0.5kg could you please help me on arriving at the permanent magnet thanks in advance

I don't think you will need a permanent magnet. Use some mild steel cylinder for your plunger. Stainless steel will not work because it will not couple with magnetic fields.

In order to achieve the force required, you will need fairly strong magnetic field. Your choice of metals for the plunger will affect the total force achieved depending on the magnetic coupling characteristics of that particular metal. Also, I am not sure how you arrived at the power level, but it may not be possible to create enough magnetic field at that low power level. Since the magnetic field will be a function of the current and the number of windings (loops) you will first determine what energy level you need to move the solenoid plunger. You will also have to find a structure upon which you can wind your coil. I would look for something similar to the size and shape you need. You can modify it or replace the wire as you need but if you are making this from nothing, you will be working very hard and you will need some good sources of materials and tool making skills.

Another thing you will find is that the right coil for your application may be one that you make by hand. A simple relay is a type of solenoid, and the resistance of those coils may be as high as a few hundred ohms. The resistance is a function of the purity of the metal and the diameter of the wire. But 12 ohms is a little too low for a coil made of a single length of wire. You simply won't have enough loops to create the desired magnetic field.

But there are several ways you can compensate. For instance you can:

1. Create a mechanical advantage by using a lever arm with a solenoid of a longer stroke.
2. Increase the applied voltage (and thereby current and power)
3. Increase the current using parallel windings (i.e. using several pieces of wire -in parallel- to form the coil

You will have to determine which approach best meets your requirements. Since this appears to be battery operated, you will have to determine what the batteries can deliver. If you want to keep the valve in the same position (i.e. "latched") you may want to look at how latching solenoids are made. Try www.google.com to search for "latching solenoids" which require no power to hold in either position. The only requirement will be the power necessary to change positions.

You can also examine some low voltage solenoids from which to get construction ideas. A typical doorbell is a simple low voltage device (albeit AC instead of DC). Also look at an old cell phone that uses a vibrator. Those can be motors or solenoids.

When you say "latch" I think of a type of device which is a "holding magnet" that maintains a position against some force. That implies that someone or something else puts it into that position initially. Holding magnets are used in a variety of things. Some of the larger ones are used to hold doors open unless released due to a fire.

Again, it will be helpful is you can be more specific. But, I hope I have given you some good ideas from which you can begin to experiment. You can design on paper all you want, but when you want it to work you have to satisfy physics.