Need help with science fair project... wireless Arduino rx/tx

[pityocamptes]

Currently trying to assist my son with a science fair project. Basically a robotic hand that basically moves up/down and left/right - sort of like the motion of a wrist. The goal is to make it wireless. The servos will be controlled by basically the same thing as a rc head tracker - you move your head and the "wrist" moves with it. We have made the headtracker using a nano and gyro board and uploaded the code we found online and it works great... according to the GUI interface that came with the code.

We found a rx/tx schematic (basically to control servos on rc plane with telemetry (which we don't need) on one of the rc forums, but the whole thing turned out sketchy... the code was in hex form and although I am ~ok with code, not very certain what was going on. Had a very tough time, and actually errors uploading the code onto a promini with cc2500 rx/tx module.

We would like to use something like a nano, and a tx/rx module that works well with it. Had no issues uploading code on the nano.

Can someone please help us moving along on this? Does anyone have a schematic for a wireless rx/tx module that basically controls up/down and left/right and maybe the ability to turn a light on/off by switch or push button on the tx unit?

I'm pretty good at following a schematic, but would need some help with code, or possibly code that already exists?

ANY help is GREATLY appreciated. My son is starting to get bummed out thinking we may not be able to accomplish his project goal. Thank you!!

 

[MikeMl]

You need a "protocol" first, followed by how to get the RF transmission from A to B.

The protocol requires periodically getting 6 to 8 data values (degrees of freedom) to the hand...
How many bits of data for each degree-of-freedom (DOF)?
How often do you need to "update" the values (message)?
Do you randomly address each DOF or always transmit all of them, even if some haven't changed since last message?
How do you validate a message? CRC? Checksum?

Get the messaging right, and the RF hardware will follow...

PS: If you are able to command the hand using just one twisted pair, then you can begin worrying about replacing the twisted wires with a radio link...

 

[pityocamptes]

Thanks. Wow, that was so far above my head. Sorry for the stupidity, new to this entire thing. Basically the headtracker unit has a PPW (I believe) signal that comes out. Need to have that to a transmitter. The receiver end takes the signal and moves the up/down and left/right servo. It would also be nice to have a switch of some sort on the transmitter that when flipped or pushed will turn a light on and off at the receiver end. Thanks.

 

[djsfantasi]

Do you have the hand already? How many servos are in it? I am assuming there are two. One for left/right and another for up/down. I'm not sure about 6-8 degrees of freedom; I believe there are those two.

What you do need is commands. One for each servo. They can be as simple as left/center/right or up/center/down. Or if you want finer control, use two byte commands. One for selecting which servo and the second mapping the servo pulse rate desired. There are many schemes possible.

Whatever scheme you devise is called the "protocol".

You can get this part running over a wired connection first. This way you can test your code for the communications protocol before tackling the wireless problem. That way you are facing one problem at a time.

Try googling "communications with Bluetooth on Arduino". You will find many examples of communicating wirelessly.

 

[pityocamptes]

Ok. Thanks. No still working on hand. Yes, it should only have two servos. I guess what I need help with at the moment is a schematic showing what arduino and what transceiver to use and how to wire them together. Next will be what code to use with this. Do you have an example of the code - can play around wit once unit is built? Also, schematic diagram? Don't really know where to start or what components I need, or how to wire them together. Thanks.

 

[djsfantasi]

Wow... I hate to break this to you. Your project is definitely do-able. But (don't you hate when someone says that?), you apparently have a long way to go before you are able to complete it. I've given you references/links on how to wire it up. I've given you sample code... And you still have no clue. I don't know how to proceed. Please do a bit of studying on your own and let us know what you've learned.

 

[pityocamptes]

Thanks again. Perhaps I am missing something, but I do not see any links? Sorry about that.

 

[Les Jones]

When I tried Googling the text string suggested by "djsfantasi" there were over 400000 results. I think there are enough on the first page to start your research.

Les.