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$10 Hackable Submarine — Parallax Forums

$10 Hackable Submarine

ercoerco Posts: 20,257
edited 2016-05-16 01:59 in Robotics
I mentioned this sub elsewhere as a joke in a now-sunken thread, and it's been mentioned in the EMIC thread. It's a neat little item all by itself. I can't say what the max underwater range is, but it worked fine in ~2 feet in a plastic bin. 40 MHz. I decided to buy a few more just to cannibalize for the 3-channel RC system for a project I'm working on. It has twin rear drive motors & props for differential thrust steering, plus another motor & thruster for up & down. It remains to be determined how much current it can handle. I'll share more details after I crack it open in the next day or two. Rick wanted to know if there was room to squeeze some Prop AI inside, but it's kinda small to begin with.

http://www.ebay.com/itm/Mini-RC-Submarine-with-Double-Propellers-Black-/291744753761

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2016-05-13 03:20
    Okay, you suckered me into it! 'Ordered one just to see how deep radio waves can penetrate salt water.

    -Phil
  • xanaduxanadu Posts: 3,347
    2' under water? That's awesome. My plan was to tether a floating XBee but that sounds promising enough for the pool.
  • WhitWhit Posts: 4,191
    edited 2016-05-14 01:41
    erco - why? You did it again! Mine is on the way too!
  • mindrobotsmindrobots Posts: 6,506
    Double drat!!! You're making today an expensive day!!
  • ercoerco Posts: 20,257
    Tell 'em erco said hi!
  • ercoerco Posts: 20,257
    Very hackable, erco's quite pleased. I "delicately" sliced open the hull with 2 slow circumferential cuts per the photos and everything pulled out very nicely. Mini 3xNiMH pack was socketed for easy removal, I replaced it with a LiPo and all's well per the video demo below. Ordering a few more for parts.

    I haven't range or smoke tested, but the tiny antenna is easy to extend and the SMT H-bridge driver transistors look beefy enough for a few hundred mA.

    @Phil: the red antenna wire is bent into a U and laying against the PCB. Both ends are soldered down, but the far end is not connected to anything. If you're range testing in salt water, you might want to drill holes strategically to pull out the antenna wire and reseal to try different antenna length & configs. How long is a 40 MHz quarter wave whip anyway, like 5.5 feet? :)



    sub1.jpg
    1120 x 672 - 190K
    sub2.jpg
    1120 x 672 - 332K
  • WhitWhit Posts: 4,191
    Nice to hear. Think I will play with mine a bit before I cut it up. Thanks for showing us the inards!
  • ercoerco Posts: 20,257
    Whit wrote: »
    Think I will play with mine a bit before I cut it up. Thanks for showing us the innards!

    Silly Whit, you know you need two, one to keep stock and one to hack!

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    'Just got mine. Had to laugh at the instructions:

    "Do not use detergent, dangerous drugs, or seawater in the pond [where you will be running it]"

    Now I'm really curious what will happen if it encounters dangerous drugs. Go crazy, maybe?

    Anyway, as soon as the battery is charged, I'm going to ignore the warning about seawater and test it in the local marina. If it works, I'll order three more to be used as prizes for my class's RC paddleboat race.

    -Phil
  • ercoerco Posts: 20,257
    I got my first of these $10 subs today. These are 49 MHz and black. The one I hacked is gray/blue and 40 MHz, bought a month ago from a different seller. The R/C systems don't overlap, so you can run 2 on different freqs simultaneously, FYI.

  • ercoerco Posts: 20,257
    edited 2016-05-16 18:30
    Phil Pilgrim (PhiPi) wrote: »
    If it works, I'll order three more to be used as prizes for my class's RC paddleboat race.

    -Phil

    Works? What's "works"? Surely it should work on the surface in salt water, then "works" is subjective, how deep it goes before losing the signal. Shouldn't get lost, it pops back up to the surface when there's no power. Plenty buoyant in fresh water, even moreso in salt.

    Obviously you'll rinse thoroughly in fresh water afterwards. I am careful with mine and still the up/down prop got stuck/seized, requiring a toothpick to free it up. That thruster is very noisy and the motor is at 90 degrees. I haven't chopped that up yet but there may be a magnetic coupling or something.

    So who'll be first to get underwater video from a now-$5 keychain camera in a watertight bag or case mounted on a sub?

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    'Back from testing. Yup, saltwater. It's conductive, and the radio waves did not penetrate more than a few inches. So in full dive and full forward, it would dolphin between the surface and 3" deep.

    I'll leave it to someone else to test in dangerous-drug-infested water. Who's up to the challenge? :)

    -Phil
  • ercoerco Posts: 20,257
    Would having the transmitter antenna underwater help? Connect a few feet of wire to the whip.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    erco wrote:
    Would having the transmitter antenna underwater help?
    Rather doubtful. I think it'd be like shorting it to ground.

    Better would be to mount a receiving antenna to a float and connect it to the sub via some thin coax.

    -Phil
  • mindrobotsmindrobots Posts: 6,506
    Is the dolphin reaction a built in safety feature: won't go more than 3 ft deep or some such thing before it auto-surfaces?

    I think you need to get an antenna to the surface (experience gathered from submarine movies) or come up with your own ELF system but that will be the worst RC system ever!!

    How about something that's a cross between an IR control and a Ping((( - you could modulate the utrasonic transmission. The problem is it takes so much energy to push a wave through water (one ping, only, Vasily), you'd probably end up cooking any of those marine critters you were supposed to be counting.
  • ercoerco Posts: 20,257
    Time for a VLF-Pal module, PhiPi!

    https://en.wikipedia.org/wiki/Communication_with_submarines
  • kwinnkwinn Posts: 8,697
    I wonder if ultrasound would work. Low frequencies like the ping uses might have the bandwidth to control it. Not much chance of sending video unless you use 10MHz or higher frequency units.
  • ercoerco Posts: 20,257
    Per https://en.wikipedia.org/wiki/Underwater_locator_beacon , underwater locator beacons use ultrasonic pings at 37.5 kHz. Same freq as many IR comms, coincidence?

    An ultrasonic control system sure sounds like a great student project, PhiPi!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2016-05-16 22:18
    mindrobots wrote:
    Is the dolphin reaction a built in safety feature: won't go more than 3 ft deep or some such thing before it auto-surfaces?

    The sub has slight positive buoyancy. When it's not receiving a signal, the motors -- including the dive motor -- stop, and the sub automatically pops to the surface.

    -Phil
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