New Project help and suggestions

[Randy5140]

I am asking for some ideas/suggestions on what hardware or processes I should/could use on a new project.

This project will consist of eight individual "stations" that, when a button is pushed, will play a recording locally, the other 7 stations and at a remote receiver.

Each station needs to contain 3 (three) switches, a speaker with amp to play a recording, a receiver to play the recording from another station and a transmitter to send the recording to the other stations and the remote receiver.

Station 1 Example:

when switch #1 is pressed a short recording will play ("Station #1 process starting") at itself, all other stations and the remote receiver

when switch #2 is pressed a short recording will play (" Emergency condition at Station #1") at itself, all stations and the remote receiver

When switch #3 is pressed a short recording will play ("Station #1 process ended") at itself, all stations and the remote receiver

I would also need to log the number of pushes of each button from each station at the remote receiver location and show the count of each via an OLED.

Its difficult to try and explain this as,, I ,,, know what I want to do,, but putting it into words is tuff!

So if I need to do further explaining please ask and i will do my best to clarify.

 

[rossko57]

Areas you could think about;

What's the communication medium and distance between stations? e.g. wireless. wired < 100m, wired 1km, piggybacking some existing network. etc.

If each outstation only comprises switch, maybe LED, and a speaker, my first thoughts would be to have all the smarts in the central/master station and just wire to each dumb end panel with CAT5, carrying switch/audio channels. If everyone is to play the same messages, a shared audio channel from a single master source is obvious.

Do you need all of the logging onscreen at the same time, or is it acceptable to allow someone to page through it? Do you need the button pushing to actually do anything other than play messages, e.g. start/stop some external equipment, or monitor it?

 

[Randy5140]

Areas you could think about;

What's the communication medium and distance between stations? e.g. wireless. wired < 100m, wired 1km, piggybacking some existing network. etc.



the system needs to be wireless, distance between stations (from 1 to 8) would be approx. 300 ft. max distance between farthest station and "remote" would be 500 ft.(line of site)


If each outstation only comprises switch, maybe LED, and a speaker, my first thoughts would be to have all the smarts in the central/master station and just wire to each dumb end panel with CAT5, carrying switch/audio channels. If everyone is to play the same messages, a shared audio channel from a single master source is obvious.

I thought about this also,, having one "brain" and everything else being receivers only. having all the "recordings" in one place might make it easier. but it still needs to be wireless as the cables would cause a safety (trip) hazard as they would need to be on the ground.

Do you need all of the logging onscreen at the same time, or is it acceptable to allow someone to page through it? Do you need the button pushing to actually do anything other than play messages, e.g. start/stop some external equipment, or monitor it?

as of now no other operation of the switches is necessary (other than logging the number of times they have been activated), they will only tell something to play the message.



This will be used outside,, I plan to use replaceable battery packs for power. I do have several Xbee pro's that I was thinking about using.

 

[hippy]

One way comms and uni-directional systems are much easier to implement than mesh or peer to peer systems. As rossko57 suggests you could have each station communicate button pushes to a master then have the master send out the appropriate audio message to all stations. The stations are then only button push transmitters and audio receivers plus amplifiers. The complexity is in the master, handling button pushes, deciding what to transmit by way of audio, and logging button pushes.

A huge question is whether this is safety critical, mission critical or more for a bit of fun.

 

[Randy5140]

Yes I agree that a master unit with the stations being simply button push transmitters/sound receivers does best.

but is it possible to send sound files via,,, for example an XBee?

yes this is safety and mission critical.

it is to try an be sure station 2 knows what station 1 is doing before they attempt their process.

I can see the "remote" unit being the master having all the messages in it possibly on a flash memory and the stations simply calling for a specific message to be transmitted/played.

or if any of you have other suggestions.

 

[BeanieBots]

It IS possible to send sound files via Xbee but sending large files will take a long time over a slow RF serial link.
If all the messages are fixed, why not have them already stored at each station?

If this is mission critical and/or safety related, what are the consequences of a message never making it?
This is a real possibility with ANY RF solution and must also be considered with a wired solution (broken or shorted wire).
You will need to have a continuous (or frequent) "are you there?" signal in the background so that each station can have a set response for when comms are not available.
It would also be a good idea to have a ACK/NACK type comms with data packet checksums even if using something like Xbee which does a lot of that for you.

As Hippy says, setting up a mesh is not a simple task but for something critical it is a must so that if one station goes down others can then attempt to pass the message on via a different route.

Please consider very carefully the implications of ANY form of failure within your design.

 

[hippy]

When a system is intrinsically fail safe there is less worry about messages being dropped or lost; things simply won't continue in those circumstances.

Having an emergency button on each station suggests that message has to get through and you need to ensure it does. Because there is no guarantee that such a signal will get through ( even with a wired system ) it will likely be necessary to detect loss of comms with a station to signal an emergency or 'stop everything' situation. Each station will need their own loss of comms detection as well to handle when emergencies cannot be reported. It all gets very complex very quickly.

The biggest problem with anything safety critical is perhaps not technical but worrying that you have not considered everything and knowing you can face extremely serious consequences if it ever goes wrong. My personal recommendation would be to steer clear of safety critical systems.

 

[Buzby]

'Safety Critical' to me immediately suggests that some form of 'Factory Approval' or 'Quality Assurance' is usually required.

Are you sure you want to go ahead with this ?. If it fails you could be in BIG trouble !.

( If it needs approval, and you don't get it, you'll be in trouble anyway. )

 

[rossko57]

You could take care of many robustness issues by basing something around a WiFi network and VOIP based intercom systems. Or perhaps a bit cheaper with an industrial style Modbus/IP setup.

 

[Randy5140]

OK,, you got my attention,,

I guess I will need to let you know what this thing is to be used for. (sorry,, I wasn't trying to mislead anyone,, just trying to protect my idea)

This project is a hobby related item.

As some of you know I fly Radio Control Airplanes,, rather large ones,, currently a 1/3 scale Curtiss Jenny. (15 ft wingspan) and am working on a 1/2 scale Ryan STA.

I recently attended the largest flyin in the United States, the Joe Nall. (some of you may be familiar with it) (check the place out,, www.joenall.com)

They have for several years now used an emergency system that consists of a button at each flying station that when pushed sounds an air horn letting everyone on the line know that there is some sort of event happening that necessitates every ones attention.

While flying there this year I noticed that with all the engine noise and people milling around there was difficulty notifying the other pilots when as airplane was taking off or landing.

Being friends with several of the people running the event (during the evening over a few cold ones) a discussion started over this issue.

Earlier in the week a couple of us were doing the above mentioned relaxation and I had mentioned that I had been playing/learning the PICAXE systems.

So,, I was asked if I might be able to improve on the system they now had in place with the emergency buttons.

Something that would alert each pilot of an immanent take off, landing or emergency.

While this does in a way concern safety it is more of a notification system of convenience as all pilots are by the AMA (our governing body) rules specify where a pilot is supposed to be in relationship to the active aircraft.

There were several incidents of an aircraft pulling out to take off while another pilot/aircraft was on final approach.

This occurred simply because the two pilots were unable to communicate their intentions to each other because of the distance between them and or the noise of the aircraft in the vicinity.

I told the people asking me to undertake this of my concerns of reliability of the system, and their response was that anything over what they had would be an improvement.

Again, I did not mean to mislead any of you in my description of the system, please accept my apology.

What I am looking for is input on what equipment, ( which PICAXE chip,, which radio system, recording storage, etc., ) in your opinions would best suit the system.

Thank you all for your concern over my involvement in this!

And,,, I am still interested in your ideas/opinions on the project.

You all are well versed in the systems and how to best incorporate the various sections together.

Thank you.

 

[rossko57]

Tell us more about the existing system - is that radio based, how does it work? Obviously you've to take care about radio activity in proximity to radio controlled aircraft, as well as observing national regs (USA only?)
Can you clarify the limitations? If folk can't hear an airhorn, will a recorded message be any better? Is the warning intended for the crowd, the hangers on, or just the pilots? Is there confusion between approach and takeoff parps, or doesn't that matter? (An obvious tweak would be a one parp for one activity and two parps for the other, still leaving multiple continuous parps for a real panic)
It might be possible to enhance/extend/automate the existing setup.

Activity logging seems a nice-to-have only? I would say its only of use if you log time and source, thats easy enough (but requires your master to keep a realtime clock)

 

[Randy5140]

Rossko57

the existing system is/are 8 water resistant electrical boxes with a push button switch on top. inside is a 9v battery connected Thru the switch to a 2.4 ghz transmitter.

when the button is pushed it sends signal to receiver approx. 500 ft. away and thru a small board and relay that activates the air horn.

Believe me,, there is no problem hearing the air horn!

When standing at a pilot station where the pilot is currently flying there should be little problem hearing a recording.

At a/the station where a pilot is taking off the noise would be a problem but since he/she is initiation the notification then not being able to hear over the engine noise should not be a problem.

At a/the station where a pilot is landing the noise level should be low enough that they even though they are initiating the notification they too should be able to hear it.

The takeoff, landing notification is only intended for the pilots currently flying or in one of the other two processes.

While we were discussing this "new" system, a comment was made about using a smaller PA system for the pilots only which could also use the recordings. This system would be positioned near the flight line with the speaker/horns pointing at the pilots.

But the main emphasis was that each station would have its own speaker to play the notifications.

The activity logging is nice to have,, it would give the operators of the fly-in additional information.

They are really into record keeping as they even have a form the they use to keep track of any crashes and what the reason is/was.

So,, being able to keep track of the number of takeoffs, landings and emergencies would give them information to work out averages between takeoffs and landings VS emergencies and crashes.

The logging, as of right now,, would only consist of the number of takeoffs, landings, emergencies.

I really don't see the need for any time logging,, like how long between the time station1 takes off and lands..

hope this helps!

Thanks.

 

[SAborn]

What frequency do the aircraft operate on? as you would not want the ground control system any where near the aircraft frequency being used.

Personally i would use a laptop as a master and do all data logging via the laptop, and use the pilot stations as a slave via the master, all slaves can be on the same frequency and each just transmits a qualifier prior to data so the master knows what slave the data is from, its far easier using an old out of date laptop that still has the speed and processing power to number crunch and store any amount of data you desire, and the picaxe slaves doing the simple tasks.

Its very easy to interface a picaxe with a laptop via wireless, and the simplest wireless modules i have found to do this is the Dorji tranceivers, but most of them are on the 433mhz frequency, which might clash with the aircraft frequency used.

 

[SteveT]

What frequency do the aircraft operate on? as you would not want the ground control system any where near the aircraft frequency being used.

The frequency of choice these days is 2.4 ghz. Although others are available.

 

[rossko57]

You have to spell it out for us dummies - is 2.4Ghz the choice for the aeroplanes or this signalling system?

I really don't see the need for any time logging

I'll bet those "really into record keeping" don't yet know it could be done easily but that's by the by for now.

I've missed the point somewhere, so re-read.
The airhorn is for emergency use _only_?
Independantly of the airhorn function, the main desire is to have each pilot-station signalling all other stations about an impending event .... and it also necessary to signal just _who_ is initiating that event?

Given that the stations may or may not be in earshot of each other, I would worry about synchronising recorded announcements. It's likely to turn into a gabble of voices. And/or get missed if one-shot, or become incredibly annoying (i.e. ignored) if repeating. Have you considered alternative "display methods" - say a beeper to attract attention, a yellow or green light to say in/outbound, and a big single digit display to say who dunnit?
I'm envisiging a box with loud beeper, buttons for in, out, emergency, a number painted on it ("me"). Three lights for in/out/emergency, and a single digit display of the source box.

It's fairly simple to expand the system into crude "ATC" for added value; say a pilot pokes his "approach" button - it issues the advisory to all others - and then _locks out_ everyone elses buttons (except emergency) for N minutes. Simple slot management? You will have to have some kind of contention resolving anyway (two pilots press simultaneously) so could take advantage.

In all cases you'll need two-way radio comms, so the existing radio gear presumably _won't_ do and you'll have a free choice as to what to use. I think a single channel will suffice, each station has only to send very simple messages - one or two characters effectively - and tag transmissions with its own ID. The boxes ignore everbody but the master.

 

[Randy5140]

You have to spell it out for us dummies - is 2.4Ghz the choice for the aeroplanes or this signalling system?

The Aircraft use 2.4

I'll bet those "really into record keeping" don't yet know it could be done easily but that's by the by for now.

Yes

I've missed the point somewhere, so re-read.
The airhorn is for emergency use _only_?


Yes for Emergency use only



Independantly of the airhorn function, the main desire is to have each pilot-station signalling all other stations about an impending event .... and it also necessary to signal just _who_ is initiating that event?



Yes,


Given that the stations may or may not be in earshot of each other, I would worry about synchronising recorded announcements. It's likely to turn into a gabble of voices. And/or get missed if one-shot, or become incredibly annoying (i.e. ignored) if repeating. Have you considered alternative "display methods" - say a beeper to attract attention, a yellow or green light to say in/outbound, and a big single digit display to say who dunnit?
I'm envisiging a box with loud beeper, buttons for in, out, emergency, a number painted on it ("me"). Three lights for in/out/emergency, and a single digit display of the source box.


Yes, I thought of adding a light at each station that would come on for a short period of time, and to have the recorded message repeat twice.



It's fairly simple to expand the system into crude "ATC" for added value; say a pilot pokes his "approach" button - it issues the advisory to all others - and then _locks out_ everyone elses buttons (except emergency) for N minutes. Simple slot management? You will have to have some kind of contention resolving anyway (two pilots press simultaneously) so could take advantage.



Yes,, emergency and Landing would take priority over Takeoff

In all cases you'll need two-way radio comms, so the existing radio gear presumably _won't_ do and you'll have a free choice as to what to use. I think a single channel will suffice, each station has only to send very simple messages - one or two characters effectively - and tag transmissions with its own ID. The boxes ignore everbody but the master.

Yes, I believe that if I use the XBee, each one has its own unique ID and that could be used to specify and trigger the correct station message.

 

[SAborn]

I believe that if I use the XBee

How deep are your pockets, whats your budget?

Are the Xbee not also on the 2.4Ghz range same as the aircraft, if so do you think its a wise choice to use the same frequency band?

 

[Randy5140]

The pockets are OK,, I already have 15 or so Xbee's on hand


Yes I believe they are on 2.4

I will do some checking with one of the radio manufacturers to see if it will cause a problem.

 

[BeanieBots]

I've used Xbee and 2.4Ghz RC equipment without problems.
The only problems I've had with them is when in close proximity to micro-wave ovens.
Range is a bit limited unless using the pro version.
You can choose different channels on the Xbee so it would be possible to develop a channel hopping system which RC equipment already does, so conflicts should be rare.
Consider making the messages failsafe. eg Rather than a message such as "it's not safe" assume it's not safe unless there is an explicit message that says "it is safe" and that message will dissapear unless it is continuously updated.

I think Xbee would be a good choice from a reliability perspective assuming a full mesh system is implemented. However, it would not be a simple solution to do.

 

[Randy5140]

One of my previous bosses once told me

&#8221; A smart man may not know all the answers. But, a smart man knows where to get all the answers&#8221;

So here I am again!

I have contacted one of the RC radio manufacturers about the use of the 2.4 ghz Xbee's while RC systems are in use.

I spoke to the guy that does the system development. (The one that started the 2.4 ghz RC stuff)

What I was told was that the Xbee's while on 2.4 would not &#8220;interfere&#8221; with the RC radios.

But, that each Xbee, would act as though it were up to 7 more RC systems being turned on.

They said that at a normal event this should not cause any problem as they use a channel hopping system; they constantly look for an open channel.

But at an event where 70 or more systems could possibly be turned on at once, the addition of the Xbee's could cause problems.

I found that the Xbee's are available on 900 mhz and mentioned it to him, and he said that would be the way to go!

So,, just for info sake,, the above might be worth logging if anyone else plans to use Xbee's in an RC environment.

With that taken care of, I am now moving to the other problems/questions on the system.

I am thinking of using an SD card in each of the 6 stations that would have the required audio recordings on it/them.

There will be between 12 and 16 recordings on each SD card (the same on all stations).

Being still rather new to the Picaxe systems there may be a better way to save the recording and if anyone has a suggestion please let me know.

The idea is: when a button is pushed, some type of message is sent out telling each station to play the message that is related to the specific button,,,,

I will try to explain: Station 1 pushes the Takeoff button. This triggers a message sent to all stations to play the recording "Station 1 requesting Takeoff"

I realize there will need to be some controls on this as to,,, does a landing take priority over Takeoff etc.

Can someone point me to any reference on the Forum regarding the best way to save/name and then pick a specific saved file for playback?

Anyone have any suggestions on how to implement this process.

I have looked on the Forum for hours using different search words but have not have much luck yet.

Thanks in advance to all!!

 

[SteveT]

http://www.picaxeforum.co.uk/showthread.php?16353-mp3-playback-module
This is what we were all playing with last year.

 

[SAborn]

I dont mean to steer you away from the picaxe, but should you want to use a SD card or USB then it might be worth you looking into the Maximite, as it has both on board and is a picaxe on steroids, also programmed in basic.

It would also permit a old (or new) PC VGA screen to be connected directly for visal messages if desired, along with a PS2 keyboard, all standard to the maximite board. ( along with about 60 I/O pins with all the picaxe functions and no math limitations)

Its really horses for courses, to what you really want to create.

 

[Randy5140]

SteveT,,,

Impressive post! Looks like it is what I am looking for!

And better yet,, something I don't have to build!

Thanks for the suggestion!

 

[lanternfish]

Just to throw in my two cents worth, and not trying to be flippant, but this sounds like an activity that is better suited to a less technical solution i.e. a form of air traffic control all communictaed via rt to a central controller that has ultimate responsibility for scheduling and informing the flight line.