Homebuilt ROVs Forum

kenl wrote:WOW, with that motor combo I think it will be a rocket!

Be careful of any exposed electrical connections, especially if diving in salt water. Once back in the air they will corrode very quickly if there is still power available them, I mean like in minutes..

Thanks for the tips kenl!

It won't be much of a rocket as it won't be very hydrodynamic It will be more like a worker style ROV.

Did a little testing today in my tank.
Not exactly the best props as I thought, but not the worst either. My ampere-meter has stopped working, so I will have to get a new one tomorrow to see what amps I am pulling.
Some pictures though:

Have you tried with two blades? Maybe the performance will increase. The air-props are not ideal for water.

ArduROV wrote:Have you tried with two blades? Maybe the performance will increase. The air-props are not ideal for water.

I have thought about that and might try it. Just want to see the difference in amp draw from 6 to 3 blades first.

Another update though.
I have noticed that there has been some doubts here on the forums about using IP cameras. Mostly because of delays.
Therefore I made this small clip showing that the delay and picture quality even on this cheap IP camera is quite good. Notice the time difference you see from where I tap my fingers to when it actually shows on my screen.

Okey. First numbers are in:

All @ 12v

2 bladed prop:
1kg = 6,5 amps
1,95kg = 23 amps (max speed)
Reverse:
0,9kg = 23amps (max speed)

3 bladed prop:
1kg = 5.5 amps.
2kg = 25 amps (max speed)
Reverse:
1kg = 25amps (max speed)

5 bladed prop:
1kg = 8.6 amps
1,8kg = 27amps. (max speed)
Reverse:
1,2kg = 26amps (max speed)

And the famous Graupner 2308.65
1kg = 5amps
2,2kg = 13amps (Max speed, but sucking some air so not really reliable)
Reverse:
0,9kg = 12.5amps (max speed)

And in order to test something else, I ordered a new prop:

4 Bladed Propeller RH 70mm M5 (G2311.70)
Also a graupner prop, but slightly larger and four blades. But has slightly less pitch then the 2308.65 prop.

Hi olegodo. All looks really good. That camera has the same delay as my Foscam imitation, but better image and much smaller! Seems the RasberryPi cam you tested earlier and some others take a while to do the compression?
Regarding the stepper motors, just a friendly word of caution. The controller board that I used has an enable line. I tied this high (I think) to enable at all times there was power to the board. Problem is, when the controller is not stepping, the motor soon gets very hot. Could be nasty or even downright dangerous with oil-filled . With 12 volt supply, current when stopped was about 700mA. Current less when stepping. Inductance........For future use I will be moving the enable line to the Arduino and only assert when needed.

rossrov wrote:Hi olegodo. All looks really good. That camera has the same delay as my Foscam imitation, but better image and much smaller! Seems the RasberryPi cam you tested earlier and some others take a while to do the compression?
Regarding the stepper motors, just a friendly word of caution. The controller board that I used has an enable line. I tied this high (I think) to enable at all times there was power to the board. Problem is, when the controller is not stepping, the motor soon gets very hot. Could be nasty or even downright dangerous with oil-filled . With 12 volt supply, current when stopped was about 700mA. Current less when stepping. Inductance........For future use I will be moving the enable line to the Arduino and only assert when needed.

That's a good thing to remember: Stepper motors use the same amount of power all the time (when enabled) but they can't cool themselves when they're 'holding' a position. Disabling between functions saves battery power and also allows them to 'coast' so if your ROV is moving the blades will be allowed to move with the current and rotate.

This shouldn't be a problem because the holding force of a stepper motor is generally required for things like robots, milling systems and 3D printers where the system needs the motor to hold fast wherever it last stopped until it's required to do something again. In a thruster motor this is not required and can be detrimental as you mentioned.

Great feedback!
Should be easy to connect the "enable" pin so that I can enable/disable all 3 steppers with one button when needed. If I end up using steppers instead of servos that is. Looks like I might as I have found a pretty simple way to waterproof them with pvc pipe, 3D printed end cap and 4mm oil seal for the shaft. All neccesery gearing can be done outside.

What diameter of pipe did you use for your hull? I'm gonna build using 1" sched 40 pvc. Got it for free so I can't complain.

I used 32mm (1 1/4" ? ) pipe.
It's plenty strong enough so 1" should be fine.