RCAP Ver 1.1- Ver 2 Development.

[hihptsi]

starting another thread regarding the testing and improvement of the RCAP GPS autopilot module.

[rclinks2002]

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[Hovertime]

Ordered my RCAP V2 board and parts kit from here:) : http://www.scalerobotics.com/store/catalog

[MAGO]

Anyone knows how work this RCAP,
it is an automatic pilot?
Only navigation, no altitude hold?
it is an element of a autopilot?
the RCAP that you bought, is ready to use? Do you need another components?

MAGO

[hihptsi]

Anyone knows how work this RCAP,
it is an automatic pilot?
Only navigation, no altitude hold?
it is an element of a autopilot?
the RCAP that you bought, is ready to use? Do you need another components?

MAGO



The RCAP is a Waypoint navagating device that accepts a nema input from a Handheld GPS via Serial connection.the RCAP reads stores Tracks or Waypoints entered into the Handheld GPS via Manual means or Via Garmin Mapsource software once waypoints are made active in the Handheld and the RCAP autopilot is activated via a extra receiver channel and a switch on your transmitter,the RCAP will then Take full control of the Rudder and steer the aircraft to the next waypoint, during this time you have full control of the elevator servo to hold aititude, or let a copilot take care of that..there are 2 adjustments on the rcap board to adjust the servo travel and the agressiveness of how it holds an activated course.At this time there is no altidude hold function but given a few more people are willing to help an altitude hold will be in the works that will be a easy upgrade to the existing RCAP Version 2 boards.i have a fully functional rcap unit that has been ground tested and dialed in and seems to be working flawlessly i will be putting the RCAP through a series of tests on my UAV to find any flaws and hopefully address them.anyone with programming experience and electronics experience willing to help with a altitude hold please give me a pm we can get the ball rolling on this.

Thanks
Walter

[MAGO]

Thank you Walter.

It can be used with ailerons or only rudder?



MAGO

[Hovertime]

I plan to test mine on RC truck:)

[hihptsi]

Thank you Walter.

It can be used with ailerons or only rudder?



MAGO

it is recommended you use the RCAP on the Rudder channel,Although i THINK it would work fine set up on aleirons IF you were using 1 servo to control the Aleirons..in theory it will work but i have not tested it this way...
Walter

[Hovertime]

No i doubt it, it would be out of control ....

[MAGO]

I think that maybe RCAP could be used with ailerons if would have an altitude hold device.
Because when the arplane turns with ailerons it will lose altitud. In that moment the altitude hold device will move the elevator (or speed up the motor) to hold the altitude and perform the turn without problems.
I am wrong?





MAGO

[Matt Dziubinski]

I plan to test mine on RC truck:)

Let us know :)

[kd7ost]

I think that maybe RCAP could be used with ailerons if would have an altitude hold device.
Because when the arplane turns with ailerons it will lose altitud. In that moment the altitude hold device will move the elevator (or speed up the motor) to hold the altitude and perform the turn without problems.
I am wrong?MAGO

No, you are not wrong. It will work as you say. Everyone needs to remember this won't generally look the same as when you fly though. When we stand on the ground and slam full sticks to crank it around, we can't get that with the autonomous parts. The rate of turn needs to be limited and you have to give it enough airspace to work and be a little patient. More trainer like.

Dan

[hihptsi]

ok i was thinking a little about the altitude hold function and come up with a couple ideas on its operation..it would be nice to utilize the 10 bit onboard ADC of the PIC 16F876 im thinking a max Ceiling of 2000-2500 Feet would be good enough i figure a motorola MPX5100 Pressure transducer given we use the max ceiling of say 2000 feet we could have a resolution of around 5 feet or less.id like to hear what you guys recommend what route we should go here.

the Existing Pic 16f876 could be reprogrammed with the altitude hold function
given there is enough space leftover..

basic operation for the altitude hold

power on: initializes (LED status),Calibrates/Zeros out (ground = 0ft AGL)

once activated (same switch that activated RCAP) Takes pressure sample and maintains Pressure at wich the autopilot was activated at.

pretty simple.id like to know what everyone thinks on this.

[Hovertime]

Well it sounds simple :) All I can say that if I have a suitable pic programmer, and firmware file, I could probably burn it, and could also solder needed parts together, thats about it .....

One could use other ready to use stabilizing devices too...
BTW altitude hold is a good idea even using rudder, or for simple straight and level flight too.

Another thought I had for less power variation due to battery voltage changes comes from my heli flying - lets consider using governor mode for the prop.

This (with the right setup) would make sure RPM is constant during the whole flight.

[hihptsi]

Well it sounds simple :) All I can say that if I have a suitable pic programmer, and firmware file, I could probably burn it, and could also solder needed parts together, thats about it .....

One could use other ready to use stabilizing devices too...
BTW altitude hold is a good idea even using rudder, or for simple straight and level flight too.

Another thought I had for less power variation due to battery voltage changes comes from my heli flying - lets consider using governor mode for the prop.

This (with the right setup) would make sure RPM is constant during the whole flight.

i was thinking about the RPM function wich will be nice,input could be via GPS or via a Pitot-static type sensor,but one thing at a time though :)

Gov mode would be a good idea for a fix but would not gurantee a airspeed,but would work for the time being.
i could very easily go out and but a UNAV alt hold and be done with it but the point of this project is a learning experience :D hopefully some more people chime in who can provide a little help to getting this done.

[radiohound]

There is a fair amount of space left over, and using the onboard adc would save code space, and be easier than implementing the ADS1100 15 bit a/d converter.

I vote for the MPX4115a because it is just about the same as the MPX5100, but slightly less error, and more importantly... I have a bunch of them for cheap.

Also like the theory of operation you have, makes good sense. Have to remember the folks trying to fly in Denver at 6000 feet and above, and me at 150 feet though. Haven't run the math to verify your results of 5 feet yet.

Walter

[Hovertime]

Had an idea (stupid? :o ) .... While searching for that pressure sensor saw this : http://www.electronicsinfoline.com/CircuitBook/Industrial_Electronics/Encoders_and_Decoders/13676.html
Optical encoder.
We could simply mount a tiny prop on that shaft and have a simple airspeed indicator optical encoder? Still need altitude sensor though...

[radiohound]

I vote for the MPX4115a because it is just about the same as the MPX5100, but slightly less error, and more importantly... I have a bunch of them for cheap.
Walter

I placed a pad for a MPX4115A on the back of the RCAP2. I have it arranged coupled to an ADS1100 a/d converter, but it looks like it may only require 1 jumper wire to get it to bypass the ADS1100 pad and get to a free analog pin of the PIC16f876a.

Early boards unfortunately have a silkscreen layer over the MPX4115a's pads :( , but I have found that 200 grit sandpaper works well for this if you are a bit carefull. I will post pictures of the back tonight.

I have not been advertising this, because it is untested, and not yet implimented.

[hihptsi]

I placed a pad for a MPX4115A on the back of the RCAP2. I have it arranged coupled to an ADS1100 a/d converter, but it looks like it may only require 1 jumper wire to get it to bypass the ADS1100 pad and get to a free analog pin of the PIC16f876a.

Early boards unfortunately have a silkscreen layer over the MPX4115a's pads :( , but I have found that 200 grit sandpaper works well for this if you are a bit carefull. I will post pictures of the back tonight.

I have not been advertising this, because it is untested, and not yet implimented.


the silkscreening will not be a problem trust me ;)..

we need to come up with a MAX altitude these things will see and choose our parts accordingly..the 10bit onboard ADC might not be enough in that case we might have to utilize the ads1100,and possibly a different Pressure transducer to gain some more resolution.let me know what you guys think..

[kd7ost]

Is that an altitude max from Sea level or from local ground level?
I wouldn't be too excited about a low altitude unit. I say don't set it below 4,000 feet agl. That leaves a huge overhead. Just my opinion.

Dan

[hihptsi]

Walter,

after looking at the specs of the motorola MPX4115A it looks rather attractive for use with the RCAP.
Minimum pressure 2.2 psi or 4.4792 inches HG
Maximum pressure of 16.7 Psi or 34.0012 inches HG
and has temperature compensation
voltage range of .2 -> 4.8 volts



in a Standard perfect atmosphere
Pressure Altitude is 29.92 inches
so this sensor would be able to read preassures Below Sea level for those living in a hole :)
we loose about 1 In HG. for every 1,000 feet gained

we should set a ceiling of say 11,000 feet ASL i think should be plenty of room for even those living in the clouds :) we need to compute the resolutions using this sensor and the on board 10 bit ADC of the PIC 16F876a
if resolution looks good we can go ahead and start implementing everything and get started on some code :)


Walter..

[radiohound]

There is some very good information here:
http://www.steveonweb.com/index.php?id=28,0,0,1,0,0

And a PicBasic Pro code for the MPX4115a and a PIC16F877.

[LukeZ]

I have a bit of info about altimeters, theory, etc... on my site, www.kansasflyer.org (http://www.kansasflyer.org) (altitude section is here (http://www.kansasflyer.org/index.asp?nav=Avi&sec=Alti&tab=Intro)). I'm using an MPX4115.

Not completely discussed on the site, but more so in this thread here on e-Zone (http://www.rcgroups.com/forums/showthread.php?t=372869), are my attempts to dynamically scale the output so that I get a resolution of less than 1 foot from sea level all the way up to 45,000 feet. I have this working currently though it needs a bit more tweaking to reduce noise, as well as some temperature compensation.

However, that is probably a bit overkill for what you need, and I don't think the code would fit on your PIC (I like to be a bit liberal with my programming - space is cheap these days).

A 10 bit ADC is not going to give you much resolution, unless the ceiling is kept pretty low. I may be a bit off in my calculations because I did them quickly, but I figure that to get 2 foot resolution you will probably need an op-amp with a gain of about 15, and with only 10 bits this will limit your ceiling to only about 2,000 feet. That's fine if you live at sea level but if you start in Denver you're already past the limit. The options are to either 1) make do with lower resolution, 2) go to a higher res ADC, or 3) use some sort of dynamic scaling as described in the thread linked above. This latter method involves quite a bit of additional circuitry so at that point you might as well have just gone with a higher resolution ADC, since that upgrade at least doesn't require much additional code - though it probably will necessitate a pretty clean board layout to minimize noise.

I'm not sure what resolution is needed to adequately hold an airplane's altitude. It may be that even something like 5 feet is fine. Then again, at 5 feet maybe you'll see your plane porpoising up and down. I have not experimented with this yet so I can't really say.


Luke

[Hovertime]

Got my kit today, nicely made board:)
What other enhancements and add ons are possible on the board itself, similar to pressure sensor? I see a few empty pads on the back of the board.

Another question, might be obvious to electronic guys but not to me - does it have provisions for in-circuit programming? Might come in handy some day, and while I don't have a 28 pin programmer I do have one with in circuit programming capability.

[rclinks2002]

Got mine today, I have built a voltage regulator so I can run the GPS, an onboard still picture camera, and the board off of a 11.1v lipoly. Very simple to put together.

[radiohound]

Got my kit today, nicely made board:)
What other enhancements and add ons are possible on the board itself, similar to pressure sensor? I see a few empty pads on the back of the board.

Another question, might be obvious to electronic guys but not to me - does it have provisions for in-circuit programming? Might come in handy some day, and while I don't have a 28 pin programmer I do have one with in circuit programming capability.

Thanks Hovertime:
Some more details are described here: http://www.uavs.net/rcap.html

You will see that A1 and A5 are added as auxilary servo connections, J8 is an extra servo connection, or input from the receiver. SW2 can let power pass from the receiver to the RCAP - through J8, or lets the RCAP power a servo. And, the unlabeled 6 pin header above J5: This header is made up of spare pins from the board that are currently unused by the RCAP. Pins from left to right: PortC,4 PortA,1 PortA,2 PortC,0 PortC,2 PortC,3


I have not published much about the back side, since I have not tested or developed code for it yet. On the back, the large 5 pads are to hold a MPX4115A pressure sensor (altimeter). The smallest 6 pin pad is for an ADS1100 16 bit analog to digital converter. In this application it would be acting as a 15 bit converter, but that should be plenty in this application. There are two connections to the RCAP for it to communicate to the I2C device.

The rest of the pads you see on the bottom are for filtering capacitors and resistors. They are for surface mount 1206 size components, which turn out to be pretty solderable, at least after a beer.

I did not place pins for in circuit programming. Great idea! I will consider adding that to future models. I would like to make it as easy as possible for people to play with the code, or at least to experiment with the code of others.

Walter

[Hovertime]

Oh, I see so thats the MPX4115AP model then, I was thinking it was 8 pin surface mount sensor type such as MPXA4115A6U, MPXA4115AC6U , but then it would make sense to put it on top of the board ...
AP type would end up on top of the board with pins going down the side and under?

Thanks for explanation, hope you guys get altitude sensing part added soon :)

BTW if I needed to reflash it I could still do it in circuit by temporary soldering a few wires to certain pins on board right?

[Hovertime]

I have another couple of questions guys...

If I decide to solder a cable instead of serial port - what pins would go where?
I guess it would need to be 3 wire cable, and connect to ground and serial in serial out? Which is which on RCAP?
I was looking for connection example in this thread: http://www.rcapa.net/forums/viewtopic.php?t=503

Hm just looked up max232A.. looks like pin 8 is in and pin 7 is out, so go accordingly to this?

And one assembly question - resonator/crystal - is there a difference which way to solder it in?
Thanks.

Off to LHS to get servo extensions, and JST pigtail and will be ready to test it out! :D

[Hovertime]

My unit is done, :D will post how it works in a different thread, to keep the clutter off of this thread.

[kd7ost]

Has anyone been using this outside yet? Has anyone seen symptoms where the LED stays on for long periods of time while enabled, and the servo quit responding?

Dan

[Hovertime]

I have, mine is not working right, and led was on all the time, or blinking at random intervals (or providing some troubleshooting code>?)
RCAP2 autopilot troubleshooting and testing thread (http://www.rcgroups.com/forums/showthread.php?t=484568)

[pistaandrea]

Rcap - Pdc 10

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Hi people.
I used RCAP some time ago. It worked on little planes. When I put it on my 38ccm gas extra acrobat, it got nearly lost.
The RCAP powers the servo only at the time of turning. When the signal to the servo has been sent, the servo stays without power. If it is a big fast plane with a big rudder, the wind blows the rudder in to the center position, the plane stops turning. The GPS recognizes that the plane is not turning and gives another input for turn. The RCAP relays this to the servo with the power lasting just for a short time, then the servo stays without power until another relay. This goes on and on and the plane flies off track.

It took me some time to find out why the plane looks like it is going for the turn, but suddenly it stops.

Well, I am proud to announce that we have manufactured a device that has the same function like the PDC 10
It is not able to suspend cross track error yet, but we are working on it. You could load in the GPS two positions named FUN1 and FUN2. When the plane gets in to these positions, the unit sends signals to servos to do specified actions – take a picture or release a load.
The unit is set by a special program box. It is 4 times smaller and lighter than the RCAP, It powers the servo all the time,
Its function is very clear from the setting process on the ground, we are not sure about the price, but it should be about 350 dollars along with the JETI program box. The alt hold and speed hold are separate units that would be available too. We are testing it.

It flies with the geko 201 and I have to say it is capable of A-B-A route flying using a little trick which we have invented.
The trick is mentioned in the manual. If there is any interest let me know. The web page for the product is in progress.
We call the unit GPSRI – GPS rudder interface.

[_helitron_]

Do you guys know that there is since a long time a RCAP 3 available already ?

http://alai.h3m.com/~s0350672/catalogo/product_info.php?cPath=43_51&products_id=205

Cheers,

//Erwin

[radiohound]

Rcap - Pdc 10

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The RCAP powers the servo only at the time of turning. When the signal to the servo has been sent, the servo stays without power. If it is a big fast plane with a big rudder, the wind blows the rudder in to the center position, the plane stops turning.

Not sure what kind of hardware you are talking about, but all the RCAP versions I am aware of keep the servo powered at all times. It also keeps pulsing out the servo direction command. This is easily seen on a scope.

Also, this summer, a stand alone waypoint sequence function for RCAP2 hardware will be coming.