Help me understand my pneumatic door system

[slipperysam]

Hi all,


I have a 2000 BlueBird CSRE. I've been living in it for a while now with the original door. The way the door operates is an on/off switch on the driver dashboard to hold it open or closed. The switch only has on and off states (it is _not_ one of those momentary electric switches). We use the switch to open and close while we're inside the bus, and when we leave the bus, we put the switch in the closed position and pop the emergency switch so that the door opens and closes manually. Then we just pad lock the outside when we leave.


I'd like to install some relays so that I can control the door programmatically. I have inspected the switch and the door itself, but unfortunately since my bus is already complete, I can't really trace back all of the wiring without ripping out my ceiling. So, I was hoping someone more familiar with this can help me piece together how it works.


Here's a picture above the door:

and a diagram drawing out that system a bit clearer (including the results of some multimeter continuity tests on those solenoids):

There are wires that go down to the light, but the light only turns on when the door is open and the keyed power is on, whereas the door itself works regardless of power being on/off.


For completeness, here are pictures of the switch being open, closed, and the back of the switch (its the golden box thing):

Also relevant perhaps: when you use the switch, you can hear some air pressure being released at the switch site.


So, with all that in mind, I hypothesize that those black and red tubes are _air_ and not electricity, and the door switch is directly sending the air to either the door open (X) vs closed (Y). Which would be unfortunate for me. Initially, I thought that the two circular items above the door were solenoids that directed the air depending on the electricity supplied to the four terminals, in which case I could just figure out what power to supply when and be done with it. Does anyone know what those things are and how they work?


Thanks for any help!

 

[Albatross]

Is it not possible to add a relay and a bypass to the outside of the door?


I'm thinking something like you could have a keypad that sends a signal to relay that opens/closes the bypass switch that essentially just jumpers the switch on your dashboard.

 

[slipperysam]

relay that opens/closes the bypass switch that essentially just jumpers the switch on your dashboard.

I think I understand your meaning. However, doesn't this assume that the door switch is an electric one? I'm pretty sure this is not the case (see last paragraph of original post). I can unscrew my dash to get a closer look and make doubly sure. Perhaps I'll do that tomorrow.

 

[ol trunt]

I wired mine like a hall way switch with a toggle (on/0ff) switch on the inside and a keyed switch on the outside which does away with the padlock.

You will need to know the function of the push pull knob--where it directs power and when and then study up on hall way switch wiring.
Jack

 

[Albatross]

I think I understand your meaning. However, doesn't this assume that the door switch is an electric one? I'm pretty sure this is not the case (see last paragraph of original post). I can unscrew my dash to get a closer look and make doubly sure. Perhaps I'll do that tomorrow.

Kind of, but not really.


Even if your push/pull open switch is entirely pneumatic, you should be able to design or copy a bypass mechanism that should allow you to activate the circuit from either location, while using commercially off-the-shelf control hardware that is designed to use an electric trigger signal. A relay can take that trigger signal and allow it to control a switch of whatever electronic size or power, and then you can use that power to control an pneumatic switch/relay/system which should then operate your door.

 

[dbsoundman]

I glossed over this thread the first time I read it but now I see your unique problem. Your door switch appears to be air/pneumatic in the same way that the air brake knob works. Most buses I’ve seen have an electric switch which activates a solenoid to open or close the door.

That being said, I think you should be able to convert your door to have a solenoid. The solenoid would simply open or close the pressurized air path to the door mechanism. Once you have a solenoid, you can control it electrically with buttons.

 

[slipperysam]

Gotcha, yeah I am understanding this better now. I'll have to watch some youtube videos to learn how to work with these air circuits, as I'm only familiar with electric, but I see now how it would be possible.


If I put a circuit in downstream from the main door switch like below (so that the main switch open state always takes precedence), could probably do something pretty simple with an air solenoid. Perhaps a device like this.

I don't really have the vocabulary to google these things. Does anyone know what the equivalent of an electric splice is when dealing with air? Specifically wondering how to go about that T shaped join on the open line.