Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 83 users online :: 5 registered, 0 hidden and 78 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Spring loaded ball valve design

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
Sponsored 
  • Author
    Message

Unread postAuthor: Technician1002 » Sat May 15, 2010 9:56 am

There is a way to directly measure the speed of a ball valve. It can be done by placing a small magnet from a broken walkman earbud in the valve inside a tight ball of wadding. Using a pair of crossed axis coils to detect moving magnetic fields, the movement will generate an electrical sine,cosine voltage pair of the magnet orientation in the two pickup coils. (much like a stepper motor waveform)

Feed this to a stereo sound card input and record with Audacity. No voltage in either coil = no motion. A voltage in either coil = motion. Use Audacity to detect when motion starts and stops.

It is possible to measure the time of a ball valve without a high speed camera.

After I return from the retreat, I can draw up a sketch of how this would be wired onto a ball valve. This will need to be done in a plastic valve.

A similar method was used to time the QDV. Due to the metal tank, the signal was not linear, but start and piston bounce on the bumper was detectable.

This can be used to detect the time on a sprinkler valve.

Edit, found a photo of a valve to draw the coils onto. Plug the sine and cosine signals into a stereo sound card and stuff a magnet in the ball valve with the poles oriented lengthwise the pipe.
  • 0

Attachments
ValveSensor.JPG
Adding magnetic pick up coils to a ball valve to detect the motion of a rotating magnet. Motion will generate sine/cosine signals.
User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: boyntonstu » Sat May 15, 2010 10:28 am

Technician1002 wrote:There is a way to directly measure the speed of a ball valve. It can be done by placing a small magnet from a broken walkman earbud in the valve inside a tight ball of wadding. Using a pair of crossed axis coils to detect moving magnetic fields, the movement will generate an electrical sine,cosine voltage pair of the magnet orientation in the two pickup coils. (much like a stepper motor waveform)

Feed this to a stereo sound card input and record with Audacity. No voltage in either coil = no motion. A voltage in either coil = motion. Use Audacity to detect when motion starts and stops.

It is possible to measure the time of a ball valve without a high speed camera.

After I return from the retreat, I can draw up a sketch of how this would be wired onto a ball valve. This will need to be done in a plastic valve.

A similar method was used to time the QDV. Due to the metal tank, the signal was not linear, but start and piston bounce on the bumper was detectable.

This can be used to detect the time on a sprinkler valve.

Edit, found a photo of a valve to draw the coils onto. Plug the sine and cosine signals into a stereo sound card and stuff a magnet in the ball valve with the poles oriented lengthwise the pipe.



That is pretty clever. Good thinking.

In my situation, the BV 90* arc handle is actuated by pulling in a straight line. Therefore the speed of anything projected from the string or spring will be traveling at the same speed.

Your method is better because it measures the actual open to close time.


An improvement on my method is to use a few lightweight projectiles that are launched from different positions.

A friend of mine compared the performance of a QEV an his spring loaded BV using the same projectile and barrel.

They were pretty close.

I will try to get the numbers.

I hope that you have a nice retreat.
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: Technician1002 » Sat May 15, 2010 11:08 am

boyntonstu wrote:A friend of mine compared the performance of a QEV an his spring loaded BV using the same projectile and barrel.

They were pretty close.

I will try to get the numbers.

I hope that you have a nice retreat.


With a high mass projectile and long barrel, the performance change is fairly minimal. With a low mass projectile and a short barrel, the performance is more dramatic.

Find out how long the barrels were and how dense the projectiles were.

This afternoon a time is scheduled for some air cannon fun. I should be able to get some better video of launches of adding machine tape. The paper drifted over the building so it was out of view part of the time and a fair amount of camera movement as I tried to get it back into view.

On the ball valve coils, each pair of coils should work fine with a total of about 20 turns on each axis to provide a signal to a line in level on a sound card. A strong magnet such as a Neodymium should provide a good motion signal. Due to the low frequency generated a sound card without a strong low cut filter should be used. Use a sound card or capture device that can function well down to 20 hz. Many sound card mic inputs are filtered to remove non voice frequencies such as pops, vibration, fan noise, etc.

I'll be eagerly awaiting your ball valve times in the near future. Who has the fastest ball valve. :P I'll be impressed with any faster than 10ms. 30-100 ms are the norm for fast ball valves.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Previous

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'