OK, I have read several places on attaching vex with GPS. Is it possible? Also can you use the easy C to program Vex to use GPS? Has anyone used GPS?
If so how? This could be very, very, very, very… cool:cool: .
why would it be a bad idea? although, there is virtually no reason do to it in EasyC (Pro) because most of the code would have to be custom. if you can find a way to link a GPS device and vex, then post pics 
Do you mean “attaching Vex with GPS” as in you having the GPS control the bot itself or just like… Have a reciever/transmitter mounted on the bot to tell its location… The second choice would definately be alot easier than having an actual global positioning satellite control the robot itself because… Well, that’s obvious lol. If someone could design a map of, say, a building, and convert it to some kind of application, you could mount a reciever/transmitter onto a Vex robot and have it drive around while tracking its every move.
Didn’t make much sense, but you get what i mean lol.
Using GPS for Vex applications is a great idea! I have seen articles written by Jon Williams for Nuts & Volts magazine that describe how to interface a GPS unit to a Parallax Stamp using a simple serial protocol. Maybe there is a way to rehost this code to the Vex Controller using Easy C. The Vex DDT software provides access to the serial port using Rx and Tx buffers.
Why would you really want to do this?
Exactly, why would you do this with VEX, mabe some sort of long range autonomous challenge??? I don’t know I really don’t see why choose VEX over any other robotics for this.
It would be an awesome idea, if you could actually get it to work.
What kind of GPS system would you use?
Something like a hand heald Garman GPS system?
Or something like Garmon’s TomTom GPS system?
And just so you know, GPS is only accurate to within like 45ft or something so unless you are planing on exploring the entire town with your VEX, then it is not a verry good idea.
The advantages of an on board GPS unit would be for precise movement in autonomous, instead of wait commands or rotation sensors you could tell the robot to go forward for 5 feet. The precision in todays GPS units is now getting to the point where that would be feasible.
That is true, but the VEX robots are so small that the few feet off in the GPS could mess everything up if it were to go say 40 feet or more.
The main reason GPS is off is because the military makes all recievers/transmitters read an incorrect distance so that, for instance, you can’t find the exact location of a hidden military base or something. Idk, it’s hard to explain. Think of it like this: in real life, if a terrorist were to use an everyday GPS system to bomb a building, they’d be off by at least 45-50 feet. It kinda makes it so that only the government has spot-on readings from their systems, which, if a terrorist didn’t have spot-on readings, they could choose a target building and miss it.
It’s not 45-50 ft anymore, they’ve allowed the GPS units to become more accurate. I think now it’s more like 10-12 feet.
While on a car trip in Oklahoma, my Garmin eTrex Vista was able to be accurate to 7 feet. If we weren’t moving and I wasn’t in the car, it might have been lower.
Perhaps not a GPS, but some sort of positioning system using fixed transmitters within a certain area. Of course, you’d have to build the infra structure for it and that might be a little over the top, but it still might work.
If you want your robot to be able to run around inside a building, you could use a local positioning system. Heres how to set it up:
Place three transmitters throughout an area you want to explore. Create a circuit that can calculate the distance from each transmitter (From the strength of the transmission). Connect this to a microcontroller, and program the microcontroller to calculate its coordinates from the coordinates of the transmitters and distances. This would probably be a lot more accurate than GPS, maybe within one foot or less.
GPS I believe is a bad idea…
-
The vex controller range is roughly 40-60 feet…
Though it could be programmed… -
The power supply isn’t very great…
The only solution is an auto-rotating battery…
(when one battery dies, a new one comes on…)
or
Solar Power
(unless indoors)
I think that would be a very good idea it would be so cool. and those of you who say gps is not very accurate, I can walk around in my house and it shows my every step to within a foot or two. Also if you connect two batteries parrallel to the vex micro controller the battery life lasts twice as long. (not seriall it will fry the controller.)
jeez this is old
i know of a way to make it so that when one batter dies it switches to the other though i havent tried it it is pretty logical
you must connect the two battery grounds to bot directly but the positives to each side in a way that the first battery powers the relay so it stays on that and when the battery goes to low (use a resistor to adjust turn off voltage) and switches to other battery
parallel might give it too much current
No, IIRC the current is limited by the Voltage available (e.g. I = E / R). If the battery is added in Parallel, the Voltage is not Increased, the current requirements of the Vex are still the same, just the capacity to deliver amperage from the batteries is now larger.
Mark you are correct when talking about “ideal” batteries. Real batteries are not ideal.
However, if the microcontroller is designed to count on the voltage drop one battery of NiCad cells experiences to be the way that it limits how much current it draws, I’ll eat my hat…
On other words, “No worries.”
Heavy M - Your caution was not a bad thought. However, Mark’s explanation, plus my offer to eat a hat, will hopefully put your mind at ease.
Blake