Help with choosing a control system for my ROV

[rvanscotter]

Extending a 2.4GHz antenna,

One of my options was to extend the TX antenna and place it in the ROV next to the RX antenna. I figured I'd lose a bit in the 100' mini coax, but I've been told that I will lose too much and It may not work. I have a Futaba T10C with the training port on the back and I can see if I can rig up a DSC signal (Direct Servo Control) to an arduino to control the three ESC. That would be a great way to get it to work, but I'll be in arduino hell for a while.

[m_g]

Hi Trogdor,
Yes, RF from an RC controller will travel through the water with a "helper" wire. My ROV is proof and it made it to 70ft. I have a small gauge wire tied to the receiver antenna on the ROV which run up the tether with an end to connect with an alligator clip to the controller. However, I haven't had to clip the wire to the transmitter antenna yet (or aerial, depending on which side of the pond), the fact that the extra tether coiled up topside is nearby is picking up plenty of signal to send through the water.
Also, the ESC's should have no problem with the 12VDC from the car batteries. Especially the newer "3S" or 3 cell Li-Po compatible ones since a 3 cell Li-Po is 11.1V. I'm running three brushed RC boat ESC's because they offer reverse, and they were on sale. But I think they were designed for 6cell or 7.2v Ni-Cad packs for an RC boat and they're running just fine off the 12.8V I'm supplying to them.
And BTW, although the many of the cool gadgets are available in the states, they're still made in china like everything else us americans seem to buy.

Hi biglakeexile. Sounds good. I have been debating various rf antenna extensions for ages now. Did you have any luck with your 22 gauge wire deeper than 70 feet? When you said you got to 70 feet, did you just run out of cable, or did you lose signal?
Thanks a lot
Mg

[derelicte]

Extending a 2.4GHz antenna,

One of my options was to extend the TX antenna and place it in the ROV next to the RX antenna. I figured I'd lose a bit in the 100' mini coax, but I've been told that I will lose too much and It may not work. I have a Futaba T10C with the training port on the back and I can see if I can rig up a DSC signal (Direct Servo Control) to an arduino to control the three ESC. That would be a great way to get it to work, but I'll be in arduino hell for a while.

extending the antenna should work just fine. I guarantee the attenuation though air is significantly greater than the attenuation though a 50 ohm coax cable of any length.

[m_g]

BUT, is it as easy as running the helper wire from the surface into where your rx stored? Or do you need capacitors/connect direct to the rx? I have read many variations.

[rvanscotter]

Oddly enough my Futaba T10 CAG has the feature disabled but the earlier version has DSC available. The Turnigy 9X has a DSC port, does anyone know what kind of signal it is (PPM) and what kind of cable is used? What about the impeadence and signal atenuation or long distances, if you could extend the DSC signal via twisted pair on a CAT4E tether that would be a great way to go.

[derelicte]

BUT, is it as easy as running the helper wire from the surface into where your rx stored? Or do you need capacitors/connect direct to the rx? I have read many variations.

I don't understand what you mean by "helper wire". If you do try connecting the two antennas together, I'd suggest ac coupling them (i.e. putting a capacitor between the antennas).

[derelicte]

Oddly enough my Futaba T10 CAG has the feature disabled but the earlier version has DSC available. The Turnigy 9X has a DSC port, does anyone know what kind of signal it is (PPM) and what kind of cable is used? What about the impeadence and signal atenuation or long distances, if you could extend the DSC signal via twisted pair on a CAT4E tether that would be a great way to go.

the trainer/dsc port is basically the same thing. they both output a ppm signal of all of the channels. the dsc port in the 9x is probably a headphone jack. the pinout should be readily available if you search for it.

as far a signal attenuation is concerned, it could be an issue depending on the length of cable and number and quality of the connectors in between. it will probably work just fine over short distances. for longer distances, you may consider using something like a lvds driver and receiver pair to convert the single ended ppm signal into a differential signal that will travel much further.

[rvanscotter]

Thats what I thought too,

My Futaba T10C has a trainer port, I'm going to tear open the training cord and connect it to my O-scope and see what the "F" is going on.

[rvanscotter]

Yes it's true, my training port is generating 9 channels of ppm data. What I learned is that I have no idea how to use a oscilloscope, so I googled it. What I saw was only a raw PPM signal with no mixing, I believe that I can select the mixing in the controller menu.

[derelicte]

by looking at that scope trace, it appears you don't have the probe's ground properly connected.

I'm surprised by the no mixing though. however that isn't the end of the world if you are driving something like an arduino. just do all the mixing in there.