[JavaDog]

Ok, once again I come to the smart people for electronics help. This isn't related to my CNC machine, rather it is for my Underwater ROV.

I received my motors and I am now working on a way to control them. I would love to use my 4-way analog arcade joysticks (they use cherry switches) for control - or even toggle switches. A software based control would be awesome, but I think that is out of my range right now. Just to make it more difficult, I am limited to 8 conductors on my tether. Three of those are used for the camera/video.

I found some interesting off-the-shelf kits that I think will work for some things. For instance, one motor will be used to vertical control - and for that I was thinking of using this kit. Looks like it will be perfect for the one vertical thruster.

Now, for the other four (or two if that is all I can manage) motors, I had looked at this kit, which seemed ideal (the two wire/10 output control would be excellent) but I don't think it has the power to drive the motors I am using? Correct me if I am wrong? Also, not sure if this kit can drive two (or more) outputs at the same time?

I also found these schematics that another ROV builder had come up with. They look great! They even look like they would work excellent with my motors too and they use cheap old PC joysticks. However, they use PIC chips - which I have no idea how to use? He has the ASM code for the PIC chips, and the chips themselves (actually the whole package) are very afforable - but how do you get the code from a pc to the PIC?? I think this might be the most promising route...

Any new ideas or thoughts would be much appreciated! Thanks guys, I know you will be able to come up with something!

[Evodyne]

Easier than the PICs are the BASIC stamps. Look at the Parallax site. These are programmed in (I'll bet you can't guess) BASIC. Your program on the PC and download to the chip via a serial cable. Actually the chip sits in a motherboard for this-you can pop it out, pop in another one, program it, etc.

The chip configurable I/O pins and can do an A/D converion of sorts. This is how the joystick would be interfaced.

The chips can talk to each other as well! They can communicate via a serial connection (3 wires-transmit, recieve, and ground). To go any distance though you might need a special driver circuit, i.e. line drivers or current loops, etc.

So, for your setup, one joystick/topside chip could send commands to a bottomside chip that would run the motors. Given the number of I/O, it could do more(pan/tilt/zoom/lights on-off).

I've got an older development kit (one motherboard and chip, cable, documentation, etc) I'll donate to your project. The software is free off of the parallax web site. You'd need one more chip and a handfull of other stuff we can figure out to make it talk over a distance. All I ask is that you pay shipping. How's that sound? Email me if you're interested.

Your ROV soulmate,

Lance/Evodyne

[JavaDog]

Lance,
I actually have a BASIC Stamp development kit floating around. I got it a while ago, and never played with it. It never even occured to me that I could use them for this project. Heck, I even know how to write BASIC code to boot.

So, is Parallax's website the best source of info for working with these guys?

Would I have to add something like their MotorMind boards, or can I control the DC motors directly like that schematic I posted did with the PIC chips?

[Evodyne]

Lance,
I actually have a BASIC Stamp development kit floating around. I got it a while ago, and never played with it. It never even occured to me that I could use them for this project. Heck, I even know how to write BASIC code to boot.

Wow! Now you sound like me. Doy!

So, is Parallax's website the best source of info for working with these guys?

You'd have to browse it and see for yourself-I really haven't played with my kit in quite a while, so I'm not really sure. In general though there are lots of good resources.

Would I have to add something like their MotorMind boards, or can I control the DC motors directly like that schematic I posted did with the PIC chips?

Do you know what motor drivers those are? I'm guessing they are direction and PWM (pulse width modulation) types. Electrically, yes, you could use these. The problem is that the Stamps are S-L-O-W and probably couldn't handle the PWM signal generation. Motor Minds or similar might be the best bet, as they free the Stamp from needing to worry about any of this.

I did see somewhere where a guy had used stamps in an ROV and had a lot of success. I don't have a link-sorry, but you might google Stamp and ROV and see what pops up.

[JavaDog]

Hmm...so I would still need to buy one of the motormind boards to get the basic stamp to do what I want - in addition to a second basic stamp. Those motormind boards are like $40-$50...more than I can spare. I like the idea of the basic stamp (I am going to dig out my kit and play with it regardless)...but maybe not for this case.

It seems like the PIC route, although more difficult (programming wise), is the cheaper alternative? Plus, I have those schematics and code to work from.

I already answered my "how do you program a PIC" question. Seems you can make a serial programming cable for just-about free.

Any other thoughts/ideas?

[Evodyne]

J.D,

Vibrator motors? Ten amps? Hmmm. There are so many things I'd like to say, but I'd better not. Hmmm again. Ten amp vibrator motors-he he he.

O.K. Back to reality. Take a look at this site. Might be interesting for you.

I looked at your motor specs. When stalled you can pull 9-10 amps per motor. Think weeds in the props! The L298 chips (the motor drivers) are good for four amps total. :frown: At four amps they will get hot pretty quick. I've attached the .pdf with the specs for the chips. Plus these are just "dumb" H-bridges, you get nothing in the way of overheat shutdown protection, etc. There are better choices.

You might get a trolling motor blade and hook it to a shaft and hook that to your motor. Put an ammeter in series (on the ten amp range), stick the prop in a pool, and drive the puppy with a car or cycle battery. Get a feeling for your current draw-you might be suprised.

Remember that the motor current is going to have to travel up and down your umbilical. Actually the sum of the current for the four motors all together. What gage wire are you using-and how long? You'll want to avoid losses in the cable.

Evodyne

[JavaDog]

J.D,
Vibrator motors? Ten amps? Hmmm. There are so many things I'd like to say, but I'd better not. Hmmm again. Ten amp vibrator motors-he he he.

Ha!

I looked at your motor specs. When stalled you can pull 9-10 amps per motor. Think weeds in the props! The L298 chips (the motor drivers) are good for four amps total. :frown: At four amps they will get hot pretty quick. I've attached the .pdf with the specs for the chips. Plus these are just "dumb" H-bridges, you get nothing in the way of overheat shutdown protection, etc. There are better choices.

Crap, didn't think of that. If I can make it so that the props shouldn't get fouled - that will help a bit. But still, I get what you are saying here.

You might get a trolling motor blade and hook it to a shaft and hook that to your motor. Put an ammeter in series (on the ten amp range), stick the prop in a pool, and drive the puppy with a car or cycle battery. Get a feeling for your current draw-you might be suprised.

I will do that and find out where we are...

Remember that the motor current is going to have to travel up and down your umbilical. Actually the sum of the current for the four motors all together. What gage wire are you using-and how long? You'll want to avoid losses in the cable.

Evodyne

Um, RJ11 cable? :stickpoke I know, I know - I will need new cable. I need to keep the cable around 8mm-10mm dia, and flexible. Any thoughts on gauge?

[Evodyne]

J.D,

Look here for a wire gage vs. current chart. #12 to #14 is "house wire" gage and can handle about 40 Amps. If you bet on never running all four at 100% you might decide to go smaller yet. You can always use tie-wraps to bundle power and data cables together into one unit. I've seen somewhere where a guy placed little floaties so many feet down the length of the cable to keep it neutrally bouyant too. One more thing (and I don't know the answer): not all insulations are equal-some will "waterlog" (bad). Maybe the whole thing (data and power wiring) all needs to go in a protective sheath???

Lance

[JavaDog]

J.D,

Look here for a wire gage vs. current chart. #12 to #14 is "house wire" gage and can handle about 40 Amps. If you bet on never running all four at 100% you might decide to go smaller yet. You can always use tie-wraps to bundle power and data cables together into one unit. I've seen somewhere where a guy placed little floaties so many feet down the length of the cable to keep it neutrally bouyant too. One more thing (and I don't know the answer): not all insulations are equal-some will "waterlog" (bad). Maybe the whole thing (data and power wiring) all needs to go in a protective sheath???

Lance

Well, at most there will be three motors running at once. That would be the one vertical thruster (which will always be on) and both rear motors. I think for simplicity I will start out with three thrusters.

Problem with a lot of those larger gauges is that they are not even close to flexible. I really wonde what companies like VideoRay and SeaBotix do for their tether. They run MUCH higher voltage/amperage than I am, and have a tiny 8mm tether - and I think it is only a 4 conductor. Sadly, can't just call and ask them - for some reason they don't like to give out info like that.

[Runner4404spd]

you want to buy wire thats called robotic cable. its very finely stranded and very flexible. we use that in industrial assembly machinery. its not super cheap but its the best stuff out there for freedom of motion.

[JavaDog]

you want to buy wire thats called robotic cable. its very finely stranded and very flexible. we use that in industrial assembly machinery. its not super cheap but its the best stuff out there for freedom of motion.

Thanks. Any idea on where to source it? I'll check google, but I thought you might have known someone with better prices...

I found this from Alpha - is this what you are talking about? I didn't even know stuff like this existed!

EDIT: Holy crap! It is over $3.50 a foot!!

[Al_The_Man]

Another thing to remember is wire current carrying capacity is based on conduit or raceway installations, if a conductor is water cooled or used in a completely different environment, amperage rating changes, the voltage drop will still exist, however.
The larger the amount of strands, the more flexibility but the cost goes up.
Another source is welding cable, but I don't know what gauge they make that down to.
Al.

[rboeser]

How many feet of wire are you looking for? I have some 4 wire stranded 20 ga. silver teflon coated with a stainless armor shield and a plastic sheath. It measures about .180" (~4.5mm). It is flexable, although not rubberband flex. With 2 runs of this wire you have 8 20ga. silver wires plus the 2 grounding armour covers. I would think you can pull 10amps for short bursts depending upon the length.

You will have to test the water resistance of the plastic cover. Each wire is also teflon covered as a backup for water problems. It is silver stranded wire, one of the best electric conductors, this should help with your amp draw.

This wire is surplus from our military. The only wire I found close to the same specs was $6.50 a foot. I was trying to sell it for $1 a foot, nobody wants it. I will donate 100ft to the cause if you can use it. I bought it for limit switch/ signal wire because of the armor cover.

Let me know if you can use it. Best of luck on your mission!

Ron

EDIT: I attached a pic but it is not showing. Email me if you want a pic of the wire.

[ViperTX]

Ah....a giant tether...hmmmm...perhaps you should rethink this....I would keep the power source at the point where it is being used....think more RC then the "giant tether".

[gar]

050809-1055 EST USA

JavaDog:

Al has a good point on cooling from the water.

Also consider sending power down at 120 or 240 V or higher and convert to low voltage at the destination. This will allow smaller wire and when appropriately designed results in lower power dissipation in the cable.

Polypropylene is very impervious to water, whereas Nylon absorbs water. I believe Hercules Powder Co. was the creator of polypropylene. It is not good at high temperatures or exposed to sunlight. Look at www.belden.com .

.

[Runner4404spd]

i would try metro wire. i don't know where you are located but they are in michigan. i use them alot if i need short sections of stuff to get drops and what not.

586-264-7390
i always deal with a guy named alex.

[Evodyne]

you want to buy wire thats called robotic cable. its very finely stranded and very flexible. we use that in industrial assembly machinery. its not super cheap but its the best stuff out there for freedom of motion.

Yeah, there is some real flexible stuff out there. I used to work at an automation firm that built control panels and I think they used MTW (machine tool wire) which was nice and bendy.

Hey JD, you can always carry the batteries onboard! No power wiring at all in the tether. Add floaty stuff or weight to get the ROV neutrally bouyant after you add a (waterproof) battery box.

Lance

[JavaDog]

Another thing to remember is wire current carrying capacity is based on conduit or raceway installations, if a conductor is water cooled or used in a completely different environment, amperage rating changes, the voltage drop will still exist, however.

Another source is welding cable
Al.

Good point, didn't think of that. Usually welding cable is pretty big/bulky though, isn't it?

I have some 4 wire stranded 20 ga. silver teflon coated with a stainless armor shield and a plastic sheath. It measures about .180" (~4.5mm). It is flexable, although not rubberband flex. With 2 runs of this wire you have 8 20ga. silver wires plus the 2 grounding armour covers. I would think you can pull 10amps for short bursts depending upon the length.
Ron

PM sent. That sounds really interesting! Thanks!

Also consider sending power down at 120 or 240 V or higher and convert to low voltage at the destination. This will allow smaller wire and when appropriately designed results in lower power dissipation in the cable.

I was worried about running that much voltage though. Of course, if I am pushing 1-9A down there, it really doesn't matter if it is DC or AC - deadly either way! I know once we go over 12v though, there are some serious saftey concerns (I know fresh water isn't a good conductor, but still). From what information I can find, it is recomended to run a line insulation monitor when you are going over 50v. Plus, I am not an electrical engineer...

Hey JD, you can always carry the batteries onboard! No power wiring at all in the tether. Add floaty stuff or weight to get the ROV neutrally bouyant after you add a (waterproof) battery box.

Lance

This was an option we were considering too. It would really limit our run-time though. Even two car batteries (or motorcycle batteries) would be very heavy, and I can't imagine they would give us very good run-times.


Important Note - Just thought of this. My connector is only rated for 5A, 125V max.

If I go with a whole new connector in a different series I can get these specs:

This connector is good to 100m:

10A, 250V a.c./d.c. 2 & 3 pole screw terminal
6A, 250V a.c./d.c. 4 pole screw terminal
3A, 250V a.c./d.c. 6 and 7 pole screw terminal
5A, 150V a.c./d.c. 9 pole crimp contacts
1A, 50V a.c./d.c. 25 pole crimp or solder contacts

or

This connector is good to 10m:

32A, 600V ac/dc rating
2, 3, 4, 5 and 7 pole

[JavaDog]

I have another question, what if I am running these motors off of a PSU that is only capable of doing 12v @ 1.5A max - and I stall the motor? Does the PSU let out the magic smoke? Motor just not get the power it wants?

[Evodyne]

I have another question, what if I am running these motors off of a PSU that is only capable of doing 12v @ 1.5A max - and I stall the motor? Does the PSU let out the magic smoke? Motor just not get the power it wants?

J.D,

What are you thinking you'll do, use batteries on the boat/dock, or a generator with an inverter and supply? I am feeling sooo especially stupid today: PSU, is that for Power Supply Unit? Probably, I'm thinking.

In general, unless you've got some type of protection, then yes, smoke will curl and rise, billowing into an ominous cloud whose murky grayness mirrors the shadow that descends upon your soul as you realize the folly of your approach! :violin: (sorry, feeling goofy after a long, long day)

...Unless you get a supply with either overcurrent limiting, overcurrent shutdown or thermal shutdown. The limiting supply would provide up to 1.5 Amps, and no more. In this case your motors would limp along. The shutdowns do just that...shutdown. And your motors do, well, not much.

The good news is most IC based voltage regulators offer protection of one sort or another. The very common 78xx series of regulators (7812 = +12V, 7815 = +15V, etc.) feature a thermal shutdown, for exmple.

In reality, I don't think this is viable though: you ARE going to need to draw some current, period. Go unregulated: batteries or an unregulated inverter off of that generator.

Lance