Fibre optic tether
Re: Fibre optic tether
I have been following this thread for a while. but what are the advantages of going fiberopti? Ofc the length of the tether can be much longer, but other than that?
Re: Fibre optic tether
You have no electrical connection! No troubles with interferences in video or data-signal. Easy to connect, cheap (cables), lightweight, very stable connection and ultimate tensile strength...., but other than that?
You're able to connect the rov with no waterproof connector (best argument)! You can connect or disconnect it while the ROV is in water. No problems with saltwater and nice feature: fiber optic cable are always in bright colors like orange or else.
Re: Fibre optic tether
And two i left:
Fiber optic cables not curls up in cold water and won't get rigid
BIG problem seen in my last mission
Fiber optic cables not curls up in cold water and won't get rigid
BIG problem seen in my last mission
Re: Fibre optic tether
Does anyone know if PPM will be converted over a fiber optic data link, I have no idea what category PPM fits into when it comes to data.
My thoughts are that I would like to use a RC 27mhz radio, convert it to ppm, and then send down the line on a fiber optic tether and then convert it back to ppm.
I have tried to do a google on it but there doesn't seem to be much info and I almost get the impression that ppm could be analoge, is that right?
My thoughts are that I would like to use a RC 27mhz radio, convert it to ppm, and then send down the line on a fiber optic tether and then convert it back to ppm.
I have tried to do a google on it but there doesn't seem to be much info and I almost get the impression that ppm could be analoge, is that right?
Re: Fibre optic tether
I've seen some fiber optic converters posted in this thread...
You have to look for converters with rs232(!) interface because many have only 2-line rs485 interface which only works with RTS and DTS for switching transmission direction(half-duplex). This converters will not run with ROV-CONTROL solution because of the non full-duplex interface won't handle this amount of control-data sended by software and control-unit. You have to look for converters with rs232 which are able to use full-duplex-mode.
BE CAREFUL - the rs232 of converters are NOT TTL. you have to use level-shifter like max232 or else to get connected. If you connect a TTL-level UART you will burn your device and maybe destroy your converter.
If you are interested in fiber optic solutions with 1 or 2 videochannels and rs232 interface for your ROV-CONTROL solution please contact me.
You have to look for converters with rs232(!) interface because many have only 2-line rs485 interface which only works with RTS and DTS for switching transmission direction(half-duplex). This converters will not run with ROV-CONTROL solution because of the non full-duplex interface won't handle this amount of control-data sended by software and control-unit. You have to look for converters with rs232 which are able to use full-duplex-mode.
BE CAREFUL - the rs232 of converters are NOT TTL. you have to use level-shifter like max232 or else to get connected. If you connect a TTL-level UART you will burn your device and maybe destroy your converter.
If you are interested in fiber optic solutions with 1 or 2 videochannels and rs232 interface for your ROV-CONTROL solution please contact me.
yes, with a microcontroller. But if you come this way = RC(pilot)-controller- fiber optic converter-controller-RC(ROV), you have to ask yourself why not using controller directly (bothside without RC) for your control-solution?Does anyone know if PPM will be converted over a fiber optic data link
Re: Fibre optic tether
Gidday Ken. PPM is digital. I had a look at the specs on the Voscom, and they state that the data can go down to DC. This suggests that whatever digital signal you put in, provided the "high" or "low" voltages of the FO transceiver and the radio are compatible and that the maximum baud rate is not exceeded, will be sent down the fibre.
RS 485 has differential signals on 2 wires. PPM does not, but this is not necessarily a problem. By connecting the RS 485 "-" to ground through say a 1K resistor and the "+" to your radio's PPM connections, it appears to the transceiver that it is connected to RS 485. Whether this will work or not depends on the interface in the FO transceiver, the PPM voltage level out of the RC transmitter, and the PPM voltage input threshold of the RC receiver. Apparently, different makes/models of RC gear can have different voltage levels.
I think your's is a cunning idea, and will work if the above mentioned conditions can be met. If it doesn't, then stick an Arduino Uno in the transmitter box, connect an RS 485 interface module and the joystick pots and that would work for sure. Arduino and interface module at the other end, with the bonus that you can send heading and depth etc back up digitally, rather than OSD.
Just about to hit "submit" and saw ROVER3D had gotten in first. He obviously types faster than me, and in more languages too![Smile :)](./images/smilies/icon_e_smile.gif)
RS 485 has differential signals on 2 wires. PPM does not, but this is not necessarily a problem. By connecting the RS 485 "-" to ground through say a 1K resistor and the "+" to your radio's PPM connections, it appears to the transceiver that it is connected to RS 485. Whether this will work or not depends on the interface in the FO transceiver, the PPM voltage level out of the RC transmitter, and the PPM voltage input threshold of the RC receiver. Apparently, different makes/models of RC gear can have different voltage levels.
I think your's is a cunning idea, and will work if the above mentioned conditions can be met. If it doesn't, then stick an Arduino Uno in the transmitter box, connect an RS 485 interface module and the joystick pots and that would work for sure. Arduino and interface module at the other end, with the bonus that you can send heading and depth etc back up digitally, rather than OSD.
Just about to hit "submit" and saw ROVER3D had gotten in first. He obviously types faster than me, and in more languages too
![Smile :)](./images/smilies/icon_e_smile.gif)
Re: Fibre optic tether
However the one I posted and bought has 4-wire rs485 (full-duplex). I got a notice from the post-office yesterday about my fiber cable, I am going to pick it up today and hopefully be able to do some tests tonight or at least in the near future.ROVER3D wrote:I've seen some fiber optic converters posted in this thread...
You have to look for converters with rs232(!) interface because many have only 2-line rs485 interface which only works with RTS and DTS for switching transmission direction(half-duplex).
Re: Fibre optic tether
Thanks guys, the two way data is not really all that important to me but I will stump up the extra to get one with duplex communication so that I can change my mind later if I want.
The chinese new year is upon us so getting a set out of China is out for the next week or so, I will try Voscom and see if I get a response, my experience is that if companies are afraid to show their prices I'm afraid to ask. There are a few duplex sets on aliexpress, this time I will ask lots of questions before buying and if they don't sound like they know what they are talking about I'll pass them over.
In the mean time I need to start designing the new ROV and topside reel.
The chinese new year is upon us so getting a set out of China is out for the next week or so, I will try Voscom and see if I get a response, my experience is that if companies are afraid to show their prices I'm afraid to ask. There are a few duplex sets on aliexpress, this time I will ask lots of questions before buying and if they don't sound like they know what they are talking about I'll pass them over.
In the mean time I need to start designing the new ROV and topside reel.
Re: Fibre optic tether
Now I have tested my fiber optic media converters and it turns out they where not quite what was promised. I specifically got the question if I wanted 2-wire or 4-wire RS485. And I wanted 4-wire for full duplex, the units I got are only 2-wire, they are however bi-directional. It bums me out a bit off course because it is not what I ordered and I can clearly see in the little folder they included in the package that they have units for 4-wire full-duplex RS485, the unit I got also already have the leds and connections for it but I guess that there is something different under the hood.
I guess I can still use these because I got a couple of MAX485 laying around. It might not be that big of a deal because the bandwidth would be enough for controlling and getting sensor data back up. But still....
I opened up a case and I am waiting for a response from the seller, I won't get my hopes up thou. It's just really annoying since they do supply the unit I ordered but sent me another one.
I guess I can still use these because I got a couple of MAX485 laying around. It might not be that big of a deal because the bandwidth would be enough for controlling and getting sensor data back up. But still....
I opened up a case and I am waiting for a response from the seller, I won't get my hopes up thou. It's just really annoying since they do supply the unit I ordered but sent me another one.
Re: Fibre optic tether
Hi Jaman,
Your case sounds similar to mine, in that you didn't quite get what you were expecting. At least you got some data capability.
I have got hold of the Australian supplier of the Voscom units and the 1 channel 2 way data pair of units is $450, a bit steep for me.
There are a few others I'm looking at around the $100 mark but I need to wait for everyone in China to return to work.
I'm busy building a bench top CNC at the moment that I want to use to build my next ROV, so that is keeping me pretty busy anyways.
Your case sounds similar to mine, in that you didn't quite get what you were expecting. At least you got some data capability.
I have got hold of the Australian supplier of the Voscom units and the 1 channel 2 way data pair of units is $450, a bit steep for me.
There are a few others I'm looking at around the $100 mark but I need to wait for everyone in China to return to work.
I'm busy building a bench top CNC at the moment that I want to use to build my next ROV, so that is keeping me pretty busy anyways.