Electronics > Beginners

How to improve Solenoids open/close response time ?

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SeanB:
Instead of zener diodes use transorb diodes, 5W ones will work well there, and using bidirectional ones will be fine, just put them directly across the terminals of the solenoids, so the spike is attenuated the most before it reaches the control board. Voltage is selected so the peak voltage, at the solenoid operate current through the diode, is less than the maximum recommended voltage of your power switching device less the maximum supply voltage from your power supply. That way the magnetic field collapses the fastest, while still allowing the power switch to survive.

soldar:
Albatroon, this is a cool and very interesting project.  Some thoughts:

The speed with which the solenoid can move is only one factor in how fast the water flow will start or stop. At these fast speeds every little thing counts.

What pressure are you using for the water? What solenoid valves are you using? Are they designed for fast response? Because there is only so much you can do with the electronics and you need to look also at the electromechanical and fluids aspects. I see there are "fast" valves that have a response time of about 20 mS and you can get super-fast valves that will respond in 2 mS.

You should try to avoid long tubes that add inertia to the fluid. The best design would be to have the valve right next to the jet orifice and connected, not to a long pipe but to a common manifold water header for all the valves.

The switching transistor should be oversized in current and voltage specs. While the solenoid armature is moving the inductance decreases a lot and the current increases a lot. And the switching voltage transients should be limited with zener diodes or other means.

Also, heat dissipation and operating temperature should be taken into account.

 

ebastler:

--- Quote from: Teledog on March 17, 2019, 04:17:38 am ---Perhaps I've missed something..but  how about sealed SSRs?

--- End quote ---

Yes, I believe you did miss something. (I'll reply since I had missed it too...) This project is not about driving relays, but solenoid-operated valves to control liquid flow. See replies 16 and 27 above.

Albatroon:

--- Quote from: soldar on March 17, 2019, 08:16:48 am ---Albatroon, this is a cool and very interesting project.  Some thoughts:

The speed with which the solenoid can move is only one factor in how fast the water flow will start or stop. At these fast speeds every little thing counts.

What pressure are you using for the water? What solenoid valves are you using? Are they designed for fast response? Because there is only so much you can do with the electronics and you need to look also at the electromechanical and fluids aspects. I see there are "fast" valves that have a response time of about 20 mS and you can get super-fast valves that will respond in 2 mS.

You should try to avoid long tubes that add inertia to the fluid. The best design would be to have the valve right next to the jet orifice and connected, not to a long pipe but to a common manifold water header for all the valves.

The switching transistor should be oversized in current and voltage specs. While the solenoid armature is moving the inductance decreases a lot and the current increases a lot. And the switching voltage transients should be limited with zener diodes or other means.

Also, heat dissipation and operating temperature should be taken into account.

--- End quote ---

Thank you for your reply, I am only using the gravity feed pressure, This allow the dropped pixels to be at lowest speed.
The solenoid valves I used is the best valves I can pay for, In this version I am using 192 solenoid valves.
Those ultra fast solenoid valves are very expensive. I Used the best Chinese solenoid valves I can find and afford.
I am fine tuning this new build step by step. stating with the control boards, Than I'll play with pressure, tubes, Orifices & maybe some RGBs :D

Thank you for your help

soldar:

--- Quote from: Albatroon on March 17, 2019, 09:39:12 am ---Thank you for your reply, I am only using the gravity feed pressure, This allow the dropped pixels to be at lowest speed.
The solenoid valves I used is the best valves I can pay for, In this version I am using 192 solenoid valves.
Those ultra fast solenoid valves are very expensive. I Used the best Chinese solenoid valves I can find and afford.
I am fine tuning this new build step by step. stating with the control boards, Than I'll play with pressure, tubes, Orifices & maybe some RGBs :D

--- End quote ---
OK, this changes how I see the problem very radically. I think you probably do not need high speed valves at all and you probably do not need to make your valves open particularly fast. You probably do not need any bootstrap circuit to make the solenoid move faster. We are talking fairly low speeds here.

Here is something I would do. Measure the time between voltage applied to solenoid and water starts flowing. Measure time between power shut off from solenoid and water stops flowing. If those two numbers are quite similar then there will just be a delay between electrical signals and water flow but that is irrelevant. If they are substantially different then you can account for that in software.

At this point I do not think making the solenoid valves act faster is going to have any appreciable effect and I would try to go with the simplest solenoid switch with a single transistor.

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