SparkFun Forums

[Zinefer]

I am creating an RC blimp, and I only have 3 motors to control on the blimp. I was thinking about using an XBee, but it seems overboard and a bit of an expensive solution.

Does anyone know of a cheaper/smaller transmitter/receiver I only need like 100 ft of range.

Thanks so much!

[leon_heller]

You should get that sort of range with the MiRF V2, given that the thing is up in the air. You could use a high-gain antenna on the ground, to make sure.

Leon

[Zinefer]

Thank you for your reply...

Does Sparkfun carry that?

[leon_heller]

Yes, I've got some of them. PICs are most popular for interfacing them, BTW.

I forgot that they have changed the names of the products. Here they are:

http://www.sparkfun.com/commerce/categories.php?c=114

I wouldn't bother with the older nRF2401A.

Leon

[Zinefer]

Ok, sorry to have so many questions, but what is the smallest PIC? And how easy are they to program?

Thanks!

[leon_heller]

I've used the PIC16F88 (18-pin), and the 18F4520 (44QFP). There is plenty of source code around, I've got some test software you can have (assembler and C) and you will find Brennen's offerings on this forum. I've also got some PCB designs.

Leon

[Zinefer]

Oh cool, would you mind emailing them to me at Zinefer@gmail.com

http://www.sparkfun.com/commerce/produc ... cts_id=228

is MUCH cheaper than an Arduino... So that is good so far.

[Philba]

What specific things do you want to do with the blimp? In particular, motor control - speed or just off/on? What kind of a controller - handheld or a PC or ?

For lowest cost, I'd look at these:
http://www.sparkfun.com/commerce/produc ... ts_id=8949
http://www.sparkfun.com/commerce/produc ... ts_id=8946

If you only need off/on for the motors, I'd look at the above T/R along with an encoder and decoder. These might do it for you:
http://www.rentron.com/remote_control/Holtek.htm look at the first two items. This would run you under $20 for the radios and en/decoders. Reynolds has lots of stuff that might work for you.

If you want more sophisticated control (like throttle), I'd use a microcontroller. The 16F88 would work well on either end. You'll also need to manage motors but that's fairly simple.

[Zinefer]

Motor control off and on would be fine... I was going to make the controller handheld...

So, what do the encoder and decoders do?

[Philba]

Basically the encoder encodes the button presses into a signal that can be transmitted. The decoder, well, decodes the signal from the receiver into "contact closures". You can use these to turn on/off transistors that control the motors. There's an 8 button remote that integrates the encoder and transmitter into one on that site - that would make for a pretty nice package.

These would allow you to put something together with no need for programming microcontrollers. pretty easy.

[Zinefer]

Ok, Cool!

Now one more question, if i still wanted to use those radios, but use an Arduino instead of the encoder/decoders would that be possible?

Thanks so much

[Philba]

sure. it's more work but pretty straight forward. you need to create a set of codes, one for each command you want to send. On the transmit side you send the codes. On the receive side you look for the codes and when you get one, do what ever it is the code is for. You might get away with using serial I/O. You'll need to try to make the transmission "balanced" - 50% duty cycle. There are a number of forum threads that discuss this in great depth.

[radu022003]

Hi i'm trying to make also an r/c with pic and xbee. I made the boards for tx and rx. I'm usign 18f4550. Baudrate 115200.
I'm having some trouble with xbee lag. For test i place on rx board a led, pic will turn on if receive on usart '1' and turn the led off if receives anything else. If i send from pc, for example, via ftdi to rx board (pic+xbee) '1' and '2' alternative the led works ok, but some times prety often i got lag,some huge lag sometimes like 1-2 seconds. how can i solve this? I tryed with 9600 baudrate also, nothing better. I tryed pachetization timeout values: 0, 3, 10, 11 same rezult. is there anyway that i cand escape from lag?

I try this one too:
from tx board (pic+xbee) i send to xbee from 0 to 9 once at one second.
on pc (connected to other xbee via ftdi) i got 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and after that a pause of 1 second followed by a lots of 0-9 bytes. i have a video too.
i can post it somewhere if need it.

[radu022003]

i forgot to mention that data goes out from pic OK, i saw them via ftdi on pc. and i connected pic and xbee only with rx, tx and gnd.