Help with choosing a control system for my ROV

[rvanscotter]

Yeah, like I said, I have no idea what i'm doing with the scope but when you said "it looks like it wasn't grounded" I figured out what I was doing wrong. I got a much better picture, and I was able to turn on the mixing in the controller.

Question: How far can you run the PPM signal on a wire? Can I run it 100' on a CAT5e directly into a Arduino?

[derelicte]

I have no idea if it will drive 100' of cable. try it and report back with the results.

[bikerbones1968]

I have a JR FM transmitter with a DSC jack. It's on the bench as I write this post wired up with a extended DSC cable to the RX. It's controlling four esc’s, driving four 750Kv brushless motors. The gear switch operates two 50W LED's via a servo relay and DC to DC step-up converter. It is also operating the camera tilt servo.

I’m happy to say its running flawlessly on 150 feet of #18 AWG shielded twisted pair.

"Fiveover" in a post from last year, used the same set-up on a piece of Cat5, 200 feet long using one twisted pair. He reported it working perfectly.

I am going to grab 500 feet of Cat5 from work probably tomorrow. I will test the DSC cable at that length and see what the results are. I assume at some point (distance) the signal will suffer enough loss it will result in erratic control or no control abilities at all.

The bottom line is that the PPM data signal has not suffered any degradation at 200 feet. So the maximum distance will be interesting to find out.

IMHO if the signal is functioning to a RX at that distance then it should work equally to a Arduino.

[bikerbones1968]

**UPDATE**

Well I am happy to report that a PPM data signal will work far beyond anything I imagined. I grabbed a part roll of 22 AWG security alarm cable. Using only one pair I soldered on my DSC cable connector and the connector for the RX. It ran perfectly and was strung out to 250 feet.

After this test I wanted to push the limits to see where it would fail so I grabbed a new roll of the same cable and again using only one pair soldered the DSC connector on one end and RX connector on the other. After stringing out the cable, about 10 trips back and forth on my property, I plugged it in... Now I am testing a total of 984.252 feet of cable!!! Guess what??? It works just as well! This is great news. I can still hardly believe it and I am thrilled to know that my only limitations will be how much pressure my hull will withstand.

[rvanscotter]

Great news!

I do have a question for you? My Futaba T10-CAG has a traininer port and the 7CH signal is TX over just two wires. Non of my Futaba RX have a DSC port, but what if I use a JR receiver that has a DSC port, that should work right? TX / RX compatibility is irrelevant when you're talking about just the raw PPM signal. Is there PPM standard, or will the pulse positions somehow get discombobulated?

What receiver did you use?

[bikerbones1968]

I have a R700 receiver. Not sure if a JR receiver would be compatible but your Futaba reciever may do the job. Do you have a electronic copy of the manual? I will look online in the meantime to see if I can find one. Check this out to see how I have my setup connected.

download/file.php?id=659

[bikerbones1968]

I found the manual and I don't see any possible way to use your 2.4 Ghz receiver. If the trainer port on your radio is truly just a PPM signal output then I can't see why a JR reciever wouldn't work. Afterall your not transmitting any RF and the receiver is nothing more than a control interface. Channel assigning and mixing could prove to be a nightmare or impossible but I am not sure how or if its possible. derelicte, what's your opinion on this?

[derelicte]

it could work. the only issue I could see is if the polarity of the signals is different (i.e. futaba uses a negative pulse and jr uses a positive one).

however you bring up a good point - you don't need a 2.4 ghz rx to do this. if you could find a 72 mhz 6+ ch futaba rx with a dsc port it would probably work just fine.

[derelicte]

like one of these:


http://www.gpdealera.com/cgi-bin/wgainf ... I=FUTL7610

that one is probably pretty expensive, though. I'd search for a futaba compatible rx with a dsc port.

[bikerbones1968]

I guess the biggest question I have would be to know what the data signal from the 2.4 Ghz TX actually is from the trainer port. Is it PCM or PPM? I would assume it would be a digital PCM data stream and not PPM. You really have to know this in order to even try it. Thoughts anyone????