ESC & Arduino Question

[Domes]

Hi I have a few questions and would appreciate any help.

1. Is it possible to get a DC motor to go into reverse with an ESC without the reverse program function?

2. If I am running 4 brushless DC motors do I need to buy 4 individual ESC? Everything I have read says I do but seems costly considering I think I need 4 with the reverse function.

3. If I can only control 2 servos with one arduino board, does this mean I must have 2 arduino boards to control 4 motors? Or can I set up 2 motors to run off 1 servo ie 2 servos for 4 motors?

[kenl]

Hi Domes and welcome ,

I will do my best and I'm sure others will correct me where I'm wrong.....

1) As far as I know if you want a motor to run in both forwards and reverse from the same ESC it must have a reversing function.

2) I have never tried to run 2 motors from 1 ESC, it may work? But if you're building a typical ROV you would probably only have the vertical thrusters running in parallel, so there would only be a saving of say $15 for one ESC, IF you could run them that way?

3) You won't need more than 1 Arduino to control 4 motors and in fact your whole ROV, unless you get quite complicated with it. As a side note to 2) above you can control two (or more) ESCs from one arduino pin, both my vertical thrusters are driven off the same pin, D4 in my case.

[TigerShark]

1. You might be able to use a relay to switch the outer two wires to the motor polarities.
2. I am pretty sure very motor must have its own due to timing issues (RPM sensing etc).
3. You should have at least 4 pwm on an Arduino. I am using 6 on mine. If you need more you can get a Polulu Maestro to run servos and PWM devices to free up the Arduino outputs. You can have an Arduino PWM output control several ESC's in parallel.

If you go look at Hobbyking.com they have reversible car ESC for about $16 or less. Several years ago we were using boat brushed motor ESC's that cost $40 each for our ROV so it has gotten much cheaper.

[Domes]

Thank you.

I am about to build my first ROV in about a month and just doing my research, all this is new to me but will make a project thread when I begin.

I think I will go with 4 cheap boat ESC's as I read car ESC's have problems being used for underwater propellers.

[rossrov]

Hi Domes. I agree with the other comments above. Unless you are going to write your own servo PWM code, then look at http://arduino.cc/en/reference/servo From what I can tell, the servo library only uses one of the 3 timer/counters in a Uno.

Personally I would not use 2 or more ESCs off the one Arduino pin, as it can be useful be able to program or, more accurately, configure one ESC at a time from your own control/joystick without having to power down the other ESC. When you get to programming the ESCs inside a sealed ROV you will see what I mean.

2 brushless motors off the one ESC will not work, unless you had them on a common shaft or geared together in sync for some reason. Brushed motors another thing altogether.

I had trouble with the Turningy Trackstar 18A, which is a car ESC, but there is another car ESC which is in common use here. Look at kenl's and BikerBone's threads - i have some of these ESCs myself but cannot remember the model/make. Also there is a National Geographic (I think) article on the web that describes a guy's ROV that he built that uses the same ESC. Boat ESCs tend to be more expensive.

Ross

[kenl]

Snap! Ross I had trouble with the turnigy trackstars as well, I spent a lot of time trying to get them programmed and then the next time I went to use them they would need the troittle end pointrs reset

[KR2_Diving]

I had trouble with the Turningy Trackstar 18A, which is a car ESC, but there is another car ESC which is in common use here. Look at kenl's and BikerBone's threads - i have some of these ESCs myself but cannot remember the model/make. Also there is a National Geographic (I think) article on the web that describes a guy's ROV that he built that uses the same ESC. Boat ESCs tend to be more expensive.
Ross

At the moment, I am running 4 of the TrackStar 18A car ESC... at the time, they were a few bucks cheaper... turns out they are a waste of money! I am now in the process of researching suitable replacements... I have struggled to get smooth and reliable reactions out of them. Overall... NOT happy with them... Not worth the cost savings!

On a side note... I have 4 TrackStar 18A Car ESC for sale... suitable for... um... Desk fans maybe...

[TigerShark]

I think the difference is the 30A Hobbyking (PRODUCT ID: HK-30A) ones are programmed seperately and don't reset when powered down. We had lots of trouble with the other kind a while back but a program could be made to set the limits on startup.

[Domes]

Anyone tried connecting a lead acid (AGM) battery to ESC and what was the results? I am going to need about 6+ lipoly battery's and is expensive and awkward and was trying to find out if the above would be suitable but can not find much information about it.

[scubersteve]

ESCs dont care what provides the voltage (lipo, lead-acid, etc) as long as it is within their specified range. (6-24v dc or what have you)
So yes, you can power them off AGM batteries if you want.
That is how I power my thrusters in my test tank.