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Topic: Arduino GPS waypoints nav for UAVS FINAL!!! (Read 13609 times) previous topic - next topic

big93

#15
Jan 09, 2008, 12:49 am Last Edit: Jan 09, 2008, 12:51 am by big93 Reason: 1
i cant promise ill have the gps soon, even though i want it soon... im on a tight budget, and it's either that gps, or a lot of electronics, and i'm intrested in learning simpler things like sensors, and lcd screens, so i can post the gps info on a screen!


CrashingDutchman

Quote
i cant promise ill have the gps soon, even though i want it soon... im on a tight budget, and it's either that gps, or a lot of electronics, and i'm intrested in learning simpler things like sensors, and lcd screens, so i can post the gps info on a screen!


Sparkfun does sell the gps for US$ 99.95, but you can get it here for a lot less (US$ 55.00): http://www.ohararp.com/products.html


big93

which gps is that?

cuz the one with 20 chans at spark are only 60...

CrashingDutchman

Well, in my country 60 is still more than 55   ;D (sorry, couldn't resist)

I am talking about the ETek EB-85A with 5Hz engine, sold for 99.95 at Sparkfun, but only 55 http://www.ohararp.com/products.html

jordi

WOW! thats cheaper, can u find us ublox for $19.99? ;D Right know working (fighting) with the home made altimeter, is working but, to much noise. The best solution (and expensive) with 15 CM for Unit is this sensor:
http://www.sparkfun.com/commerce/product_info.php?products_id=8161
and i don't need to worry about the analog stuff, sounds tempter, but no money.  :'(

CrashingDutchman

You could try to get a sample, I think freescale sell something like the mpx4115A altimeter. With a 12- or 16 bit a/d converter you can get a nice resolution. It could use the built in Arduino a/d converter, but it is only 10 bit.

jordi

HEHE, wow same mind. Actually is exactly what im doing, using free samples altimeters from freescale and ADC with 16 bits of resolutions (i2C interface), maxim free samples, but i have lot of noise!!! I need some op amp, i making a lot of tests.

CrashingDutchman

I also experienced a lot of noise with the pressure sensor I mentioned earlier. I never tested with the a/d converter thoug, not sure if that would give better results.

Does the noise give a lot of difference in altitude? You could take, let's say, 10 samples and take an average. Would that help in your case?

big93

lol i'm confused... i dident mean to say that u were wrong, but i wasn't sure what the gps that the other site was selling

how many chans is the one from that website for 55?
also, how accurate is the temperature and other info?

an example i thought of:
if i do put it in a helicopter... can the gps sometimes freak out and say that it's like 15 degrees of course and the helicopter will try to over correct itself? do i have to average the readouts?

CrashingDutchman

The ETek EB85A is 32 channels. What do you mean with accuracy of temperature?

For your other question, I think Jordi should answer

jordi

Oh yes.. actually the GPS is not for the arducopter, is for arduplane, but if you wish to use it in arducopter (for navigation only, no for stabilize)you need to use kalman filters, magnetic compass, and accelerometers. But arduino cant handle it. Maybe in the future when arduino 16 bits or 32 bits born, could do it.
The arducopter project is just Gyros+accelerometers+Kalman filters to stabilize the heli.  
Right now im concentrating myself in the Arduplane project, because is cheaper  :D , latter when my income increase i will  buy a better Heli and try again.

-My investigations about the IMU (Inertial measurement Unit) can be used by helicopters and airplanes too. Is the most difficult thing about automatic pilots.  Almost done.

-The GPS is done.

-Altimeter, is solved, ill use sparkfun altimeter with SPI. (resolution of 15 centimeters for unit).

-Servo control is done.

Mixing this (IMU,GPS,Altimeter,Servos), you are able to do a fully autonomous R/C airplane.

Extras:

-Modem to send data to ground, done.
-Ground Station, done.

Another thing you might wonder is about switching between autopilot mode and manual mode. Well is a little bit complex to explain (with my low English skills), but ill use a mechanical switch (to void any possibility of lost control if hardware fails). I show you:




big93

so the gps has a gyro in it? and a temperature thingy? and a pressure sensor?

but to be honest, i just want to use the gps to make it aware of its geographical location, and know where to go from flight plans i give it. the gyro and such can help stabilize it, but i want to use the gps's capability of knowing where it is.

but since it wont be able to work with the arduino for now... i guess i dont need it for what i want to do.

mymonkeyandme

Quote
... you need to use kalman filters, magnetic compass, and accelerometers. But arduino cant handle it.


I was thinking about IMUs and was wondering exactly that. Do you have any experience how many (Kalman-filtered) sensor channels you can handle in one arduino? Will the problems be timing related or memory related?

Oh, and... great project!  :)

CrashingDutchman

Big93,

You should read the manual of the GPS device: http://www.ohararp.com/files/EB-85A_UserManual.pdf

It has no temp sensor, no gyro and no pressure sensor. You need to get separate items. The GPS can give you information about where it is. The Arduino is fast enough to handle the GPS information, but doing all these things (ie. Kalman filter, etc...) requires probably a lot more memory (program space)


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