Valve Control System for Powder Flow

Hi mjawad - Since this is your homework I will only kick start you (because your is in electronics).

clue 1 - The mass {weight} of a sample will be proportional to the volume for a given density.

clue 2 - The rotational position of a stepper can be controlled electronically.

clue 3 - The volume should therefore be controlled by the number of steps or (partial) revolutions.

I am not going to suggest a "pump" because I don't know the material. If you are really in trouble ask again!

There's a huge choice of ways how to implement the project. Btw, all what you need is quite googable. Ok, one more hint. Why don't you use stand alone (intermediate) device to secure predefined weight of powder?

Search in Google for Load Cells & Pneumatic Actuated Knife Gate Valves

We probably need more information to understand what you already know and have tried.. but I'll just start from the beginning.. and you can pick up where you see fit.

1. valves are devices that control the flow of some matter, typically a fluid.

2. If the matter is not fluid, then then basic problem is a matter of metering, or controlling the amount of matter delivered to the process or system.

3. With this type of system, you can combine the prime mover with the controlling device. An example of this is a farm silage unloader in a silo. A toothed-edge helix is used to move the silage to the chute for flow, while the assembly rotates around the profile of the silo to ensure even removal of the matter. Over time, the entire silo can be emptied, and the rate of delivery is a function of the helix rotation, and the rotation of the helix assembly.

There are many variations on the theme, but I think this captures the essence of it. You must create a method of uniformly moving the powder. At the exit point of the system, you can have a weight controlled tip bucket, where a spring release mechanism can be set to the desired weight. Once the force of the spring is overcome, the bucket tips.

Chris

Wow That is one heck of a "hint" and I like it so I will contribute my best way to move powder. If the powder quantity is fairly small I have used plastic flexible screw conveyors. If the quantity is larger then metal screws with VFD for control after or before being weighted out.

I used this type of method to control PH to within .25 on a process that grew crystals in the wine country in California. My product started at a PH of 3-3.4 and I had to control it at 5 +_ .25.

Do not try to use valves for powder you will go nuts, spend a lot of money and it will not work well. Screw it on to a load cell and the dump it into a hopper to be screwed into your process. Need and hand bring your work to Vegas and we can talk over a beer.

You can still stick to your stepper motor based valve control but have a loadcell on the output side and use it as a feedback to tune your steps on the stepper motor.I am incorporating the same principle for some food automation products ;basically spice powder control.I am however using a PID controller for higher productivity!

Wish you all the best!