The Seadoo GTI Sea Scooter is a simple conveyance, consisting of a DC motor and a big prop in a waterproof casing. By grabbing on and firing the motor, it can be used to propel oneself underwater. However, [ReSearchITEng] had problems with their unit, and did what hackers do best – cracked it open to solve the problem.
Investigation seemed to suggest there were issues with the logic of the motor controller. The original circuit had a single FET, potentially controlled through PWM. The user interfaced with the controller through a reed switch, which operates magnetically. Using reed switches is very common in these applications as it is a cheap, effective way to make a waterproof switch.
It was decided to simplify things – the original FET was replaced with a higher-rated replacement, and it was switched hard on and off directly by the original reed switch. The logic circuitry was bypassed by cutting traces on the original board. [ReSearchITEng] also goes to the trouble of highlighting potential pitfalls of the repair – if the proper care isn’t taken during the reassembly, the water seals may leak and damage the electronics inside.
Overall it’s a solid repair that could be tackled by any experienced wielder of a soldering iron, and it keeps good hardware out of the landfill. For another take on a modified DC motor controller, check out the scooter project of yours truly.
Fun, but I want to see one converted to Otto fuel!
https://en.wikipedia.org/wiki/Otto_fuel
Back on topic, what kind of batteries are used, I have been thinking of making one of these since the early 90s, I missed out on a chance to buy a Russian titanium one rated to something ridiculous below 1000m. Not sure how the divers survived or if it was just rated that high to be attached to the hull or airlock.
These things have existed since the start of scuba diving. Jaques Costeau and his diving buddies welded some together running on car batteries and French starter motors just after WW2. They also existed in the 80’s looking almost exactly as the one above, but having the reed control a relay. They are really simple because a prop acts as a soft start and torque converter. No need to ramp up current slowly, a bang on off switch suffice.
wow it is a great news for scuba diving. Sea Scooter, want to try it one day.
I have two units that I am not using much.. so have decided to make a twin engine unit with reverse.. the controller cannot be used as its one direction only… therefore I am still using a differnt type of prox switch and an old water softener tank ( emptied) to store two batteries in and a set of old waterskis cut down.. this will be used only for snorkling… but should have the power needed to move anyone around…. I have no idea what the controller would be used for other than switch the magnetic switch to real time power to the motor… there are three smaller wires within ( small red, two black and a green).. I cannot see any usefull purpose for this other than feedback. but its all one speed anyway.. so I am not using them… Now that its taken apart, I can now make my own cct with battery level indicator inside the tank which is now about the size of the scooter itself, and can reverse the motors… if I wish to use it differently… added boyancy is accomplished by attaching floatation onto the skis.
just something to do in my old age…if anyone inows what the smaller wires are, that would be helpfull. it comes from the motor compartment which I did not take apart…
anyone have a pic of th board after mods?
Waooo I really love to do Scuba diving once I will go to my abroad trip to Malaysia then I will sure try Scuba Diving with such SEA scooter.