Creating a control for a platform with pneumatic brakes

Thread Starter

SS23

Joined Dec 12, 2019
24
That was becoming apparent.
Let’s clarify for the sake of the OP, as their posted schematic will not work, and the introduction of a dump valve alone, or with the indicated valve, will not work.
To be honest, after 40 years of Millwrighting throughout industry, I too am confused about the terminology. It does appear though, that industry standard counts ‘ways’ as ports, and positions as potential spool positions. I see a / appearing, and have run into foreign manufactures using different terminologies, but NA usage has been standard, in my experience.
With that being said, I recommend that the OP consider replacing the indicated, 2 way, 2 position valve, with a 3 way, 2 position valve. If a quick dump action is desired, include that as well.
Yes you're right. 3-way, 2-position valve is what I'm trying to find out more about now. I will post some found options for further feedback. It's been very fruitful to see your discussions and then to see a solution emerge.
 

Thread Starter

SS23

Joined Dec 12, 2019
24
Hey everyone! Thanks a lot for this fruitful discussion so far. I couldn't work on it since posting, had a covid scare at workplace and had to test and other protocols. But finally everything's good and I am searching for 3-way 2-position valves. Will keep you all posted for further feedback, I still need to also think about creating a switch based control for this valve - OPEN/CLOSE the valve simply. Thanks again so far!
 
generally, the compressor should be fitted with an automatic drain valve at the lowest point. https://www.grainger.com/product/13X522

Not exactly lowest. So we had air lines go above the ceiling for probably 100 feet. At that drop we put in an automatic drain valve to get the water out.

Our compressor was used for intermittant sandblasting, and air for equipment valves. It also had an electronic dryer for the air.

Each piece of equipment was fitted with a filter/oiler/regulator/water separator. The valves were vented to the vaccum pump stack. We had a system of pipe to vent vacuum pumps.

Most of the valves needed oil in the air lines, especially the air to open/air to close cylinders. Those valves are special because the vents had adjustable needle valves to control the exhaust air.

I had bought about Fifty 24 VAC valves that could be manifolded in sets of 10. You basically set them side by side with an o-ring between each valve and fastened them with 4 threaded rods.

I had to take every one apart and clean every one in an ultrasonic cleaner before they were put into service or they would buzz like crazy. That was really annoying. The problem was dust during manufacturer was causing the buzz.
 
What do you have in mind for the actual brakes? The parking brake side of a standard brake chamber uses spring pressure to hold the brakes. You put air to it to pull the spring back and release the parking brake. Universal types cost about the same as a quality two position valve.

Edit...

Never mind. I reread the original post after I came home and realized I missed some details.
 
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Thread Starter

SS23

Joined Dec 12, 2019
24
Hey everyone! I found a 3-way Solenoid valve that remains normally closed. Also, as we had discussed, when its OFF it stops the connection b/w INPUT and OUTPUT and rather connects the OUTPUT to atmosphere, which is exactly what I want(to release the pressure in the brake circuit).

MY question is, to create a wall mounted switch to manually OPEN/CLOSE it, what other parts would I need?

I thought of using an Electromechanical Relay that could allow me to also control it using signals from LabView (PC - D/O data acquisition card - Relay - Valve ON/OFF). But could a system in parallel for MANUAL also work?

About Solenoid Valve: OMEGA SV-242 6W 3-Way Solenoid Valve
https://www.omega.co.uk/pptst/sv240-thru-sv270_series.html
 

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GetDeviceInfo

Joined Jun 7, 2009
1,866
Braking systems are often driven by the motion controller. No motion commands = brake on. What are you using to drive the carriage? Is this your dyno .
 
I don't 100% know what's going on, but...

I built a system that could control 24 DPDT relays, MOST were destined for valves. There was a SHUTDOWN signal from a panel/panics etc that killed power.

Each channel on the front panel had a rectangular labeled latching push button, color coded (Idec) with LED indicators for the actual state. Next to each switch there was an LED which showed the computer's state (ON/OFF) and third, there was a miniature switch that selected computer/manual control.

The only thing I did wrong was not suspend the relay board so it could be worked on without removal. e.g. replace a soldered in relay. Relay board was commercial, My LED driver board was proto. ULN2003's.

This was in a 2U case. Two 37 pin connectors went to a convertabox where the solenoids were. So, the solenoids and relays mounted on a L-shaped steel plate. The pins in the connectors could easily be removed, The valves were manifolded.. The valves had the ability to be operated manually (on the valve) with a screwdriver,

Outside in the back, there was a 10 position, screw terminal connector. This would handle non-valve stuff. e.g. RF on.

There was supposed to be another "interlock box" that would have prevented certain valves from being open, would have blinked the valve light if you were trying to open that valve. This was an afterthought.

When I said mostly valves, all but two were mounted on that case. Two were mounted near the double acting air cylinder.

A few of these interlocked valves needed valve state switches.

The safety/manual aspect has to be taken into account as well. The safety panel was keyed, The key stayed in the panel at all times. it was on all of the time. The key would be needed to reset it. During upgrades, the key was removed from the panel.

The safety panel was sometimes disconnected from the fire alarm when there were no experiments, but we didn't want to loose vacuum and there was fire alarm testing. The FAP would not be able to shut down the system. I added eventually, a LED that indicated ON, if the FAP had reset the contact and off when it had. So, we knew when the FAP came out of trouble.
It was an obvious internal disconnect that was indicated on the front. That was done with Hydrogen and Hydride gas alarms as well. They were in another room. 2 conductor monitored contacts with an EOL resistor would have been the way to go.

So safety, maintenence, operation and lockout/tagout you need to look at.
 

Thread Starter

SS23

Joined Dec 12, 2019
24
Hey everyone! I was offline from the forum for quite some time. The project was postponed due to our lab maintenance and hence I stopped working on it. But, now I am restarting work on it and have done some more fact finding about making the pneumatic brakes work.

So I have some queries, maybe some of you could comment on that: @KeepItSimpleStupid

1. Can I use a dual input relay to allow two separate inputs to control the solenoid valve?(One input from PC-D/O voltage signal, other input from a push button switch to activate the relay).

2. Also, how can I ensure that only one of these inputs works at a time?

About the Solenoid valve: 3-way 2-position solenoid valve 24 VDC power supply.
 
You need to read this: https://library.automationdirect.com/valves-for-pneumatic-cylinders-actuators/

Your brakes COULD be dual cylinder. It would have two ports. The valve would put a bleed in the other port, so you can control how fast the valve opens or closes.

Single port type valves are say air to open, spring to close and they would "vent" the air from the cyliner when the valve closes.

You can also have valves that have an air pilot meaning it acts like electricity.

You have to watch if you need lubercated or unlubercated air.

You need to get that sorted out.

Like I said before, I had a mini control panel for the valves.

The valves were TTL controlled using a ULN2003 IC. This IC takes a high to open, a low to close and disconnected gets you a low.

one side of the DPDT relay powered the valve (My case 24VAC).
The other side of the DPDT relay powered the built-in indicator. e.g. a rectangular switch. http://www.farnell.com/datasheets/164261.pdf (My case 24 VAC)

There is a good reason to use 24 VDC and not AC like I did.

I used another ULN2003 (you can get a similar part in 8 channels). to drive a small LED with a resistor.
This presented the computer control value, so there was no surprises.

A Switch near the button selected computer or manual.
e.g.
The computer turned it on or the big labeled button on the panel turned it on depending on the small switch.
You knew what the manual state would be and you also knew the computer state, so no surprises.
 
Can I use a dual input relay to allow two separate inputs to control the solenoid valve?(One input from PC-D/O voltage signal, other input from a push button switch to activate the relay).
How about a SPDT momentary switch? Connect the common to the relay, NC to the PC, and NO to your power you would use as your push button power?

Edit... I may have missed the mark a bit. A switch could create a safety issue in the event someone tries to run the switch at the wrong time. If I were doing this with a microcontroller I would have an overall manual mode switch that would signal the microcontroller to enter manual mode. It would stop the motor movement, apply brakes, and finally allow the manual switches, buttons, and such to be active. The manual controls would be connected to the microcontroller that way the microcontroller is the only thing controlling the system. I don't know what you are working with so that may also be of no value to you.

I'm a bit out of my league, but the project sounded interesting. Good luck
 
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I looked at your diagram again and:

a) think about a valve at every brake. You may have a lot of air to dump.
b) Think of pilot valves. An electric valve operates a valve needing air.
c) look at e-stop circuits
d) Look at the design of safety relays.
 

Thread Starter

SS23

Joined Dec 12, 2019
24
Hey @KeepItSimpleStupid I am working on the setup for connecting the solenoid valve with two-input relay. I will post soon my idea with a scheme. I am also looking into your suggestion for type of valve.

@geekoftheweek I am planning to finish this project soon. So stay tuned, might need some feedback! Thanks for the suggestion too. I'll post my idea soon
 
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