I'm jumping in!

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olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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 :P 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:
Attachments
Temperature of the 50A ESC after all the testing and running at 50% for 20mins.<br />Note that this is without cooling and an ambient temp of 28c
Temperature of the 50A ESC after all the testing and running at 50% for 20mins.
Note that this is without cooling and an ambient temp of 28c
DSC_0155.JPG (238.07 KiB) Viewed 3041 times
Close to max speed. pushing around 2kg (4,4lb). I have no idea what amps I am pulling here though. In reverse it managed around 0.9kg.
Close to max speed. pushing around 2kg (4,4lb). I have no idea what amps I am pulling here though. In reverse it managed around 0.9kg.
DSC_0152.JPG (247.19 KiB) Viewed 3041 times
I also tested one where I removed 3 of the blades, performance increased a bit
I also tested one where I removed 3 of the blades, performance increased a bit
DSC_0158.JPG (175.14 KiB) Viewed 3041 times
How the original fan/prop looks. 6 blades with way too steep angling.
How the original fan/prop looks. 6 blades with way too steep angling.
DSC_0157.JPG (172.08 KiB) Viewed 3041 times
Had to print a piece to mount the EDF fan to my test rig.
Had to print a piece to mount the EDF fan to my test rig.
DSC_0146.JPG (256.14 KiB) Viewed 3041 times
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ArduROV
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Joined: Oct 17th, 2013, 5:21 am
Location: Germany
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Re: I'm jumping in!

Post by ArduROV »

Have you tried with two blades? Maybe the performance will increase. The air-props are not ideal for water.
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olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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.
Attachments
screen shot of display
screen shot of display
ROV test.JPG (138.34 KiB) Viewed 3039 times
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olegodo
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Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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)
Attachments
DSC_0171.jpg
DSC_0171.jpg (165.03 KiB) Viewed 3024 times
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olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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.
rossrov
Posts: 383
Joined: Feb 28th, 2013, 5:01 pm
Location: Australia

Re: I'm jumping in!

Post by rossrov »

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 :shock:. 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.
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: I'm jumping in!

Post by a_shorething »

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 :shock:. 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.
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olegodo
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Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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.
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2014-08-01 18.34.00.jpg
2014-08-01 18.34.00.jpg (487.21 KiB) Viewed 2974 times
ssrc30
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Joined: Aug 1st, 2014, 12:26 pm
Location: Alberta, Canada

Re: I'm jumping in!

Post by ssrc30 »

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.
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olegodo
Posts: 222
Joined: Aug 30th, 2013, 9:47 am
Location: Bergen, Norway

Re: I'm jumping in!

Post by olegodo »

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