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Diver Propulsion Vehicle


(Tom-Vidar Salangli) #1

Hi
I am having some thoughts about building a DPV(Diver Propulsion Vehicle)
My thoughts are using four T200 thrusters.
I want to make it as simple as possible. Just ON(Full thrust) and OFF
I want to make it run in two speed steps
(two thrusters)=slow speed
(All four thrusters)= Full speed
I want to trigger the motors with two magnetic reed switch
Can this be used to trigger the ESC’s(one for each)
http://www.ebay.com/itm/Reed-sensor-module-magnetron-module-reed-switch-MagSwitch-For-Arduino-NEW-BU-/261760653213?hash=item3cf226979d:g:4M0AAOSwk5FUsQkn

Can the ESC be programmed to go for full speed while triggered?

So my biggest challenge here is:
Battery package(type and size)(as light as possible)
Runtime… e.g 1 hour at full speed

I guess there will be need of only a quite simple electronics?
(Controlling T200 with external ESC)
what size of the electronics-tube)

Does anyone have any ideas on how to set up the electronics and battery pack?

My design I will reveal later :wink:

  • Tom-Vidar Salangli

(Harold Scadden) #2

Not to spoil your day … I don’t think the units would have enough thrust. These units are wonderful for small ROV’s etc. but to pull a person through the water you are going to need a MUCH larger propeller to increase the amount of water you are pushing with the units and something to scale the torque up for the propeller … like a gear box or frankly a larger motor that runs high torque and low speed with a bigger prop.

 


(Tom-Vidar Salangli) #3

Not even four of these T200 pushing together?
They are specs to push around 5kg each…on max speed

e.g these are only two thrusters…https://www.youtube.com/watch?v=FRc3QDkudRk
I understand they are quite more powerful, but the propel doesn’t seem very much bigger.’


(Harold Scadden) #4

Stupid question … how much do you weight and how much drag will you create in the water with diving gear on.

To drag my big butt through the water at 113 Kg … do the math.

 


(Tom-Vidar Salangli) #5

Ok, I see.
Guess these are to small for the project then.


(Rusty) #6

Tom,

It all depends on how fast you want to go. Four T200s will definitely move you through the water, but not very fast. If this is for SCUBA diving, then a lot of the drag will come from the tank, BCD, air lines, etc.

These (https://www.youtube.com/watch?v=9Tsny1mJGR0) supposedly have about 30 kg of total thrust and you can see that they obviously work. With four T200s you’d have 20 kg thrust.

Best,

Rusty


(Tom-Vidar Salangli) #7

Hi

Thanks for reply Rusty

I will not need to go that fast.

5-6 km/t would be enough

Can you tell me anything about the type and size of the recommended battery pack for a run time of 1 hour?

How can I trigger the ESCs by Reed switch?


(Rusty) #8

Tom,

You’ll need a pretty large battery for 1 hour. Here’s an example calculation.

Assume 4 T200 Thrusters running at 75% thrust (210 Watts each, 840 Watts total). In an hour, you will use 840 Watts * 1 hour = 840 Watt-hours of energy. Let’s round that up to 1000 Watt-hours to account for some margin and so we don’t completely discharge the batteries.

If you’re running 4s lithium polymer packs the voltage will be 14.8V and the total number of amp-hours required will be 1000 Wh / 14.8V = 68 Ah. That’s a large battery. Here’s a 10Ah battery that could be connected with seven batteries in parallel to provide 70 Ah. (http://www.hobbyking.com/hobbyking/store/_64438__Multistar_High_Capacity_4S_10000mAh_Multi_Rotor_Lipo_Pack_US_Warehouse.html)

We also have a battery guide and calculator on our documentation: http://docs.bluerobotics.com/battery/

For the reed switch, I would recommend using an Arduino microcontroller and measuring the reed switch. When it is connected, you can turn the thrusters on. I can describe that in more detail if you’d like.

Best,

Rusty


(Tom-Vidar Salangli) #9

Thanks alot Rusty

Yes, I understand. Any DPV’s need big battery packs. This is what I thought it to be like. I guess you recommend me not to Look for cheaper pack at EBAY…

Please tell me more about the microcontroller setup.

 

 


(Markus) #10

The microcontroller would look for a signal on the reed switch (either high or low). You would write the code such that when the switch is closed, the microcontroller sends the appropriate PWM signal to the ESC. This way you can also adjust the motor speed by setting the PWM level in the code.


(Rusty) #11

@Markus - Exactly right.

You could also write the program to have several output level and touch the magnet to the reed switch momentarily to switch to the next level. For instance, you could have off, 50% power, 100% power.

-Rusty


(Tom-Vidar Salangli) #12

Thanks guys.

I am a noob to microcontrollers.

Can you post a link to a good one?

And how to program it?


(Jacob) #13

There are endless resources, tutorials, and help forums available for the Arduino platform. I recommend starting with an Arduino board like this one https://www.arduino.cc/en/Main/ArduinoBoardUno

You would set the speed using the servo library included with the Arduino IDE (integrated development environment).

-Jacob


(Tom-Vidar Salangli) #14

Thanks alot for all info, guys.
I guess I’ll go back into my cave and start thinking… if it is worth the effort(enough DPV-speed vs work and money)


(Kristiaan) #15

Working on about the same subject (diver-assisted propulsion when filming underwater, in order to get more smooth movement in the film), I found out that using Lithium batteries, although by far the most interesting battery technology available regarding power efficiency, might pose a serious problem from a totally different kind: you are not allowed to transport high-capacity lithium batteries by air transport. Have a look at the IATA rules concerned. So one might have to use NiMh batteries instead.


(Steve) #16

It looks like this thread is dead, but I have a couple observations. I’m using four T200s to push a person sitting in the water at 4 mph with a 4S battery (13.2V). Although a soft start is better for the T200s (easily done with an Arduino) you can also easily create a PWM on/off using a 555 timer circuit for a couple of bucks. Servo exercisers from Hobby King start at $6.