which microcontroller to use?

[tater1337]

I've cut and pasted this a bit from the parallax forum(forgive any mis-edits), but the reasoning is the same, and it looks like picaxe is a cheaper route, but maybe not an easier one......

we are planning a bot that will use two servos to hunt for a radio beacon, which microcontroller should we use? I knoew everyone has their favorite but we want the cheapest, simplest controller available, I was looking at picaxe SX series but maybe I should go with the basic picaxe 2?

what we are doing is taking a radio beacon in a remote location, using the picaxe to run 2 hobby servos to home in on it using 2 recievers with dipole antennas, looking thru the documention about it and it looks like a good match.

good, yeah, the size is fine, power will gome from a 7ah gel cell so size is not too relative. the BS1 looks like it would bareley work, as i'd end up using 4 pins for two servos, giving me only 4 pins for directional input. in theory i think i only need two, but it would be nice in case i need more.

oh, I've been vauge about the application. directed rocket recovery system. a steerable parachute, and possibly guidance for the rocket itself in later design phases. if the BS2OEM works we shoudl be able to grab a few homework boards and use them instead.

oh I bet you'd like to see some video of our project http://www.youtube.com/watch?v=Yaz_t6IBAKs

more at http://www.youtube.com/tater1337


had to get an FAA waiver plus the OK from the civlian and military ATC (standard procedure, easy peasy). aerotech I 284 for a motor, although that does have a removeable motor mount for just about any size engine you want.

but thats not what the picaxe is for, I figgure i need about 3-4 of them for recovery guidance for the HALF scale (18 ft long 40" dia)

anyone wanna do the programming? hey picaxe? want some free* advert space?

*free as in send me some picaxes to get it working

I can understand the headaches on guideable(?) recovery, havent researched it yet, like the collapsing cells idea, and might steal it. and we do plan on autonomous guidance in the future, but we figgured doign the recovery first will soften the paranoids to the active guidance on large model rockets. I bet bunny would like it if we could steer a rocket safely away from people in a lawn dart moment.

ok, I've decided not to go the foxhunting route, but find a garmin etrex and give it a target for the recovery systems, so which picaxe do I need to read an input off the GPS and then run a couple of servos? might need a compass module too(i dont think so)

 

[manuka]

Welcome- we really would appreciate more insights on DISTANCES, FREQUENCIES,terrain,your budget, resources, skills & time frame. In general the Picaxe family offerings (of which there are now 16 => http://www.picaxe.orconhosting.net.nz/pcxtype15.jpg ) are ~an order of magnitude cheaper than similar spec. Basic Stamps! We may be baised, but many consider them easier to use too-I'd many years with BS2 & certainly prefer the PICAXE approach overall.

Stan - old ham (ZL2APS) fox hunter,often over many miles of rough terrain, hills & water.

 

[moxhamj]

Ok, GPS and then transmit the data would work. What is the format of the data coming off the GPS? Baud rate, RS232 or TTL signal levels or something else? If the packets of data coming off the GPS are small (<=14 bytes) then picaxe is perfect. How far do you need to transmit the data? The antenna might be sitting on the ground, or very close to the ground, maybe sideways too, so range could be a lot less than expected. There certainly are picaxe solutions.

 

[tater1337]

decided on not using foxhunting, but will use gps. sounds like the garmin etrex will interface easily. I wont be transmitting anything from the rocket, well not until we decide we need telelmetry. basically i want a chip that can read the GPS, match it against storred coordinates, and move two servos to steer the rocket in the right direction.

I downloaded the editor, and played with it a bit, looks like a 14 should do the trick (08 doesnt have servo cmds) and be morethan capable.

 

[hippy]

You will probably want to use a larger PICAXE, say 20X2 or 28X2. The 14M ( even 08M ) may do the basics of what you need but it seems sensible to have the capability to do much more. Any extra cost will be minimal in terms of the entire project.

 

[tater1337]

You will probably want to use a larger PICAXE, say 20X2 or 28X2. The 14M ( even 08M ) may do the basics of what you need but it seems sensible to have the capability to do much more. Any extra cost will be minimal in terms of the entire project.

I looked at them, seems each step up tends to add more specialized pins and stuff that could eventually confuse me, so I picked the 14 for a starting point. the 08 looked a little too small and doesnt support servo commands(maybe it can PWM and i'd do the math, but why?)

 

[Dippy]

Have compared the required code in PICAXE and Stamp?
Why do you think PICAXE is much more difficult than Stamp?
(I'm rusty with Stamps as I haven't used them for years - far too expensive).

 

[tater1337]

ok, which PICAXE to use?

Have compared the required code in PICAXE and Stamp?
Why do you think PICAXE is much more difficult than Stamp?
(I'm rusty with Stamps as I haven't used them for years - far too expensive).

I dont think the code is difficult.

picaxe is based in the UK, and years ago when I came across them there wasnt much for support(i dotn even think the manual was out then) here in the US. seems every version of the picaxe has a different pin combination with inclusion of specialty pins.

now it appears to be a different story. well, maybe. I dont see development board for the picaxe here in the US, aside from 3rd party boards. and there seems to be only one US supplier.

downloaded the editor and played with it. looks good. downloaded the manuals, and they seem good also.

maybe part of my prejudice is from the fact that Parallax was the first place i looked when searching for microcontrollers. right now I am trying to see which picaxe i should use, so I guess I am converted.

 

[womai]

Also, regarding the more advanced Picaxe types (e.g. 28X2 or 20X2), no need to be afraid of the extra features compared to, sy, a 14M. The basic operation for all Picaxes is the same. You only use the advanced features when you need them, but otherwise you can just disregard them and they won't hurt you.

 

[eclectic]

@tater.

Re your post #8
“now it appears to be a different story. well, maybe.
I dont see development board for the picaxe here in the US,
aside from 3rd party boards. and there seems to be only one US supplier.”

Firstly, Picaxe homepage > distributors
gives four US / Canada sources.

The US picaxers could supply more information,
as to other local sources.

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