Building an RC submarine (kind of from scratch), don't know where to begin

Discussion in 'The Projects Forum' started by MinuteHand, Nov 14, 2010.

  1. MinuteHand

    Thread Starter Member

    Nov 14, 2010
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    Hello, I'm new here. I'm working on a remote control submarine with a group of people and I'm going to be handling powering the submarine and the transmission of RF guidance signals from controller to submarine. We plan on housing the electronics inside PVC tubing and I have to propel 3-4 motors using C batteries.

    However, I am very, very new to the world of RC and hobby vehicles. Textbook instruction and working with theory only go so far, and I don't know how to bring that into the real, physical world. I've never really built anything substantial before. Also, I've never had any instruction on RF.

    Is it possible to buy a transmitter such as one for an RC plane, and use that to control the submarine? I know water doesn't permit easy transmission of signals, so can I swap the frequency crystal in the transmitter for one of a lower frequency?

    I also don't know how to have the RF signals received from the antenna translate into turning on the motors.

    I think my plan of attack is:
    -Figure out power requirements according to what needs to be powered
    -Figure out how to have RF signals received from antenna turn on motors when prompted
    -Design schematic/circuit design
    -Design and purchase PCB
    -Solder everything together according to circuit design

    I've been doing research, but I feel very overwhelmed and would love advice from electrical engineers or RC enthusiasts. Help on where to begin would be very much appreciated. Thank you.
     
  2. thatoneguy

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    Feb 19, 2009
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    Airplane Frequencies can't be used for ground craft the last I checked. (FCC Rules, Not Physics)

    There are RC boats around, the problem with the sub is radio waves don't work so good/at all in any depth of water, so you'll need to have an above surface antenna.

    What size is the finished sub going to be? Is this a school project?
     
  3. MinuteHand

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    Nov 14, 2010
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    The submarine will be roughly 10 inches wide, 10 inches tall, and 36 inches long.

    Frequency crystals are manufactured commonly at 1.8432 MHz. I think the lowest allowable frequency for amateur use is 1.8MHz. I was hoping I could use this frequency, and stick the transmitter's antenna underwater to help avoid refraction loss. Having an above surface antenna is an option though.

    This is a school project; the mechanical engineering team is still deciding on what kind of motors/pumps they want to use, so I have to wait on them to get specific.
     
  4. thatoneguy

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    What type of body of water will this be for, and at what depths?

    Would light be an option for control?
     
  5. MinuteHand

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    Nov 14, 2010
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    The submarine will swim to depths of up to 10 feet in a swimming pool.

    I did calculations according to formulas I found here: http://www.qsl.net/vk5br/UwaterComms.htm and found at 1.8432MHz and at the legal maximum for swimming pool conductivity, I'd experience attenuation of only .32 dB/ft. Not sure how right that is though. I also understand the difficulty of the ideal antenna length of such a low frequency.

    I have to ask, what do you mean light? Optical fiber? I'm allowed any type of non-tethered communications method.
     
  6. thatoneguy

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    Modulated LEDs that can be sensed by a photo-detector, like a remote control for a TV.
     
  7. MinuteHand

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    Nov 14, 2010
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    It's a possibility, but all of the commercially available model submarines I've looked at operate at 27 or 49 MHz; I don't wanna get too creative.
     
  8. thatoneguy

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    If you aren't well versed in electronics, creating a transmitter and receiver would be extremely difficult, whereas IR has known ICs for encoding/decoding.

    To have RF control, I'd suggest a commercially produced model for submarines.
     
  9. MinuteHand

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    Nov 14, 2010
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    I see your point, it's pretty easy to find cheap IR ICs. I have to think about what I want to do, whether it's trying for an IR based setup, or commercially available RF "kits". I'll do some research to see what's out there.
     
  10. jpanhalt

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    Jan 18, 2008
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    Are you licensed to use 1.8 MHz?

    There are RC submarines. Have you searched and seen how they do it?

    John
     
  11. Kermit2

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    Feb 5, 2010
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    Radio control cars etc. are all 27 and 49 Mhz. Radio shack has a large selection. They are cheap and the controls can be taken from them and used directly in another model. A hack a day keeps my boredom at bay! :)
     
  12. jpanhalt

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    That is wrong.

    Here are the official FCC frequency allocations for model use. In the US, you will find 2.4 GHz and 75 MHz in common use for surface (and sub-surface :D) use. Of course, 2.4 GHz is probably not too good for subs unless you have a surface antenna.

    John
     
  13. windoze killa

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    Hey guys,

    Firstly you are assuming he is in the USA which he hasn't confirmed so FCC rules may not apply. He has made reference to VK5BR which is an Australian callsign (doesn't mean he is in Australia either).

    Secondly being in such a small swimming pool I would suggest he possibly look at ultrasonic transducers. There are plent of waterproof ones that could be adapted.
     
  14. Wendy

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    Mar 24, 2008
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    Actually toys regularly use 27Mhz and 49Mhz in the USA. They generally depend on the 10mw rule, and a generic Mhz number covers a heck of a lot of ground. It can have 10,000 or more different channels.

    This low power means it probably wouldn't be acceptable for your use.

    While you probably shouldn't use aircraft frequencies, the same equipment can be set up for ground frequencies simply by using appropriate crystals in the transmitter and receiver, no license in the USA is required. The crystals are meant to be easily interchanged, just look up a rig for a high dollar RC car, the transmitter/receiver is pretty standardized.

    The point about the country of origin is a good one, you will note most of the old hands have this as part of their profile, and it shows up on the posts.
     
  15. MinuteHand

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    Nov 14, 2010
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    First, thank you for the replies everyone. I really appreciate the help.

    I need to obtain licensing for frequencies? It was in the amateur band, so I thought it was fair game. I live in the USA. I'm still up in the air about what transmission method to use. Someone even suggested Bluetooth. I'll look into the pros/cons of ultrasonic transducers.

    The rules of the game have changed (significantly). The mechanical team wants to have 4 propellers in various positions around the submarine. They will each be in their own compartment, with their motors powered by their own C battery and controlled independently (with each receiving their own signals. I thought I was going to have a more centralized approach, but they figure the unit'll be easier to seal (and no wiring running around the unit) if we go this route. Any thoughts?

    I have looked at other submarines/hobbyists, but their exhibition always seems to favor the mechanical/structural/propulsion aspects of the submarine. They never focus on the power/transmission stuff, it's always "we just used these batteries and these kits".
     
  16. Kermit2

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    THAT is wrong. I did not mention anything about surface or subsurface :) use. I said the 27 and 49 Mhz range RC controls are common in toy cars and trucks. Proof of that fact can be found at the Radio shack web site, Look at the majority of their car and truck RC toys and you will find they are offered in 27 and 49 MHz flavors.

    Sorry but your wrong about me being wrong. But better luck next time, since I'm known to make mistakes on occasion. Do you?
     
  17. jpanhalt

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    Sorry, my friend, you said,
    "All" does not mean "many" or even "usually." It means "all."

    RadioShack has a poor selection of cheap equipment. It certainly doesn't come close to state of the art nor is it representative what serious RC hobbyists use.

    I didn't bring up and post the correct information to start a pissing contest. I felt it was and still is important for the original poster to be aware of other and probably better options for what is looking like a relatively complicated project. There is a large segment of the modeler community involved in RC boating, including submarines. Why re-invent the wheel? A simple search on RC submarines (and related subjects) will turn up a wealth of information on water-tight enclosures, antennas, and reception depths/distances in both salt and fresh water.

    If the OP is near any clubs, the best advice I can give is to contact one of them. Modelers are anxious to share their knowledge.

    John
     
  18. thatoneguy

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    Feb 19, 2009
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    At 27Mhz, a rather large power output would be needed From Tx, or an extremely high sensitivity Rx with a good antenna.

    One solution would be coax floating to the surface on a chunk of wood to hold a small antenna, and use one of the spread spectrum 2.4Ghz radios in the sub at the other end of the coax. This is the same frequency range that bluetooth runs in, so the solution would be the same. Not elegant or pretty.

    I've only seen R/C boats in use, and the range on those wasn't so good. Airplanes have excellent range, but they were on a different frequency and power, not to mention the receiver is line of sight for a long distance.

    I'm still thinking about IR control, or ultrasonic, using Pulse Code Modulation for commands.
     
  19. MinuteHand

    Thread Starter Member

    Nov 14, 2010
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    thatoneguy, that is a really creative solution to the transmission problem, haha. I'll keep that in mind if I do go the RF route. IR is viable, but I'm not sure the ultrasonic method. I neglected to mention that our submarine will house a sonar unit too (for finding objects on the bottom of the pool), and the ultrasonic waves may interfere with the sonar operation. I still have to do my research on IR/ultrasonic.

    jpanhalt, good point about the hobbyists. I'm also soliciting help from hobby forums, and they are indeed eager to share their knowledge and help me.

    As I mentioned before, the mechanical team wants to have all of the propellers operate (and be powered/transmitted to separately). This means each propeller will be like: (undetermined transmission receiver)->ESC->battery->motor->propeller. I think.
     
  20. bertus

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