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        Discussion RC Radio Tx - Re-inventing the wheel!

#1 IanJ Apr 19, 2010 03:17 PM

RC Radio Tx - Re-inventing the wheel!
 
Hi all,

I started FPV and long range RC flying by using a 430mHz Tx by way of a standard Futaba 9C connected by way of the trainer port to an extrenal 430mHz system (Thomas Scherrer's LRS).

Then I designed and built a joystick which by way of an internal Arduino pcb connected to the trainer port of the 9C. Flying my Quadcopter using the joystick is a blast, but the trainer cable and forgeting the 9C was by me on the ground I was always tripping over it.

So (I must be mad) I re-invented the wheel by building my own standalone Joystick Radio Tx using a couple of old PC joysticks, an Arduino and the Tx pcb from Thomas Scherrer's LRS kit.

It's powered from a 1500mAh 3S Lipo. About 4hrs continious use I reckon, charge socket is on the side.
Battery voltage detection sounds a buzzer at 10.8vdc or less.

There's a bunch of buttons on the top along with an 8*2 LCD which I've yet to do much with, probably trimming, dual rates etc etc etc.

Here's a couple of pics.

PS. Internal wiring is a mess......I've no patience for neatly laid out home projects.....:-)

http://www.ianjohnston.com/images/st...V2/ianjtx1.jpg

http://www.ianjohnston.com/images/st...V2/ianjtx2.jpg

http://www.ianjohnston.com/images/st...V2/ianjtx3.jpg

http://www.ianjohnston.com/images/st...V2/ianjtx6.jpg

#2 IanJ Apr 21, 2010 06:10 AM

Here's my build blog (work-in-progress) if anyone wants to do their own:
Click here.

UPDATE 05/07/12:

Download the code over at my website here:-

http://www.ianjohnston.com/index.php...bbies&Itemid=8

Ian.

#3 Naxos Apr 25, 2010 04:11 AM

Very nice, thanks for posting. I love reading about this kind of stuff. Please let us know how it progresses.

I've thought it would be really neat to build up some kind of full-on FPV system like this but I just don't have the time...

#4 sv650touring Apr 25, 2010 08:14 AM

Very, very cool. I always wondered why a more cockpit-like controller wasn't available.

What do you have controlling Ch4/rudder?

#5 IanJ Apr 25, 2010 01:08 PM

Hi,

Rudder is controlled by twisting the grip as per usual flight sim use of joystick.

Ian.

#6 waqa Apr 25, 2010 02:38 PM

Your project is very nice. I don't think its re-inventing the wheel, especially if your wheel does exactly what you want :p

What model Thomas Scherrer's LRS are you using?

#7 IanJ Apr 25, 2010 02:53 PM

Quote:

Originally Posted by waqa (Post 14939590)
Your project is very nice. I don't think its re-inventing the wheel, especially if your wheel does exactly what you want :p

What model Thomas Scherrer's LRS are you using?

V4.

I purchased the pcb without the enclosure etc.

http://www.webx.dk/rc/uhf-link3/tx_v4_03t.JPG

#8 sonicj Jun 15, 2010 09:19 AM

ian,
i tried the first version of your code and it worked with zero tinkering! it took me longer to figure out i had the wrong crystal than it did to breadboard and upload the code! good stuff!

i think i'm going to build a dedicated tx similar to your second version but im new to the arduino thing and have some questions...

there a specific reason to use the Nano V3.0 or can i use something like the cheaper Pro Mini 328?

Quote:

float AI_Raw_Batte; // Ana In Ch.4 raw var - 0->1023 (requires DP for batt voltage)
what does DP mean? (Donkey Puncherello?) do i connect the battery V+ directly to this pin?

what is thermal intelligence?

great work so far! looking forward to flying something with a joystick! cheers!
-sj

#9 IanJ Jun 17, 2010 03:54 PM

Hi,

Pls post some pics......!

DP = decimal point. The battery voltage display is useless if it doesn't display at least 1 decimal point.
You'll need to fit a couple of resistors, i.e. a voltage divider, in order to scale down the battery voltage to something under +5vdc max. Don't connect your battery directly to the input or your fry it.

I just used the Nano 3 for the ease of use & size etc, but I guess you can use any of the Arduino range provided it has the correct spec/inputs etc.

Thermal Intelligence (TI) is very specific to the Spectrolutions QuadCopter system. If you are not using it then just ignore the functionality, it won't upset anything.

Ian.

#10 Wizzard033 Jun 22, 2010 01:16 PM

Great work, I'm watching intently! :D

#11 sonicj Jul 02, 2010 03:20 AM

Quote:

Originally Posted by IanJ (Post 15342061)
Pls post some pics......!

DP = decimal point. The battery voltage display is useless if it doesn't display at least 1 decimal point.
You'll need to fit a couple of resistors, i.e. a voltage divider, in order to scale down the battery voltage to something under +5vdc max. Don't connect your battery directly to the input or your fry it.

i had a bit of a mechanical hurdle to deal with... i disassembled my donor joystick some time ago but with plans to use the insides from a rc tx. piecing it all back together proved to be a challenge! the sucky part is that it already had the option for analog outputs at the flip of a switch before i went in and started hacking up wires :o doh!

anywho, i'll get some pics up as soon as it starts looking a little less like a squirrel's nest!

do you happen to have a simple schematic for your setup? i saw on your first design you had a cap on the 5v to the pots and a cap on the 12v to the tx... do you feed the buttons +5v? how should i go about calibrating the pots? right now, im only getting movement from the servos when the pots are in the middle half of their travel.

my serial lcd is currently displaying rates and voltage, but it looks whacked out at the moment. (sparkfun 16x2). i'll have to adapt your code to accommodate the SF LCD driver. did you consider moving the lcd to its own digital pin? i think that should take care of your problem with the updates confusing the lcd.

i think my slow stick is gonna be the guinea pig for the maiden. good stuff!
-sj

#12 IanJ Jul 02, 2010 11:42 AM

Quote:

Originally Posted by sonicj (Post 15450306)
i had a bit of a mechanical hurdle to deal with... i disassembled my donor joystick some time ago but with plans to use the insides from a rc tx. piecing it all back together proved to be a challenge! the sucky part is that it already had the option for analog outputs at the flip of a switch before i went in and started hacking up wires :o doh!

anywho, i'll get some pics up as soon as it starts looking a little less like a squirrel's nest!

do you happen to have a simple schematic for your setup? i saw on your first design you had a cap on the 5v to the pots and a cap on the 12v to the tx... do you feed the buttons +5v? how should i go about calibrating the pots? right now, im only getting movement from the servos when the pots are in the middle half of their travel.

my serial lcd is currently displaying rates and voltage, but it looks whacked out at the moment. (sparkfun 16x2). i'll have to adapt your code to accommodate the SF LCD driver. did you consider moving the lcd to its own digital pin? i think that should take care of your problem with the updates confusing the lcd.

i think my slow stick is gonna be the guinea pig for the maiden. good stuff!
-sj

Hi,

The input range of the analogue inputs is 0-5vdc, so your pots must sit at around +2.5vdc in their centre position, going to 0vdc one way and +5vdc the other way. So you have 3 wires to each pot.......+5vdc, signal, 0vdc.

The buttons are easy, the Arduino digital inputs have pull up resistors internally, so you basically hook the switch up to 0vdc. So you have 2 wires to each switch.......signal & 0vdc.

The caps on the +5vdc etc are just to help smooth out the supply. Pick any size you like.

Calibrating the pots isn't easy......but then again, you don't really have to as I found the stick doesn't have to be so precise, especially if like mine you remove the spring-to-centre.
If you do want to calibrate the pots then you'll have to modify the code to write the pot value to your LCD then tweak the code till you get centres correct. But like I said, I don't think you need to as long as your mechanical setup is good and you are getting near 2.5vdc at stick centres.

Be careful with LCD drivers, as some of them I found can interfere with the timing and what you end up is a glitching PPM. The serial LCD that I use doesn't suffer this at all. Timing is important for this project.

#13 sonicj Jul 02, 2010 03:49 PM

cool, exactly what i needed to know! i can trim mechanically if need be.

the lcd im using is similar to yours, but 16 x 2. sparksoftlcd.h

i was wondering about timing last night... i viewed the ppm on the scope and it looked kinda loose, or poorly defined. the i remembered that the the rbbb i was using on my solderless breadboard uses a ceramic resonator instead of a crystal. not sure if that would cause a sloppy ppm signal or not.... i'll try it with another board tonight to see if that tightens it up.

cheers!
-sj

#14 Yorbid Jul 02, 2010 09:54 PM

I have been following this project for a while and have ordered a some parts to get started. While I would love to use the Long Range xmiter you, (IanJ), are using, I am going with the 2.4 Futaba module from HobbyKing. I have one in my 8Us and am happy with it. The idea is to be able to plug in a 2.4, 72, or 50 Mhz module. I had planned on making a single-stick box, but when I ran across this thread it was time to re-think and the Jstick looks like fun. I have dismembered three stick so far to get the parts and pieces I need--thank goodness for thrift stores.

sonicj : I see you go to OpenMoCo. Neat project. Between Tom's timescapes and MoCo there is plenty to keep one busy.

Keep up the building, Ian, and thanks for sharing.

#15 sonicj Jul 03, 2010 03:05 AM

Quote:

Originally Posted by Yorbid (Post 15456227)
sonicj : I see you go to OpenMoCo. Neat project. Between Tom's timescapes and MoCo there is plenty to keep one busy.

ya know... i was so focused on getting my lcd working for another project that i didn't even realize what that site was all about! i've played around with some time lapse on my xl2 & a little with chdk. adding motion control sounds awesome! i just tried installing, but apparently i broke macports at some point :(

this is one of my favs:
beautiful things

sorry for the thread-jack!

what board are you using Yorbid?
-sj


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