Power Disintigration

Hi, I currently have a 12 volt car battery hooked up to three TReX Jr. chips simultaneously. At the battery terminals, I am getting 12.5 volts. At the other end of the 50 ft. tether, I am getting 1.14 volts. This is through 24 gauge solid wire and while I am testing the voltage the line is connected to the chips. I was wondering if the power could be lost through the line and/or the chips are drawing enough power to bring the total voltage down to 1.14 volts but not enough to actually power the chips. None of the lights on the chips are illuminating.

Thanks, Jacy


24 gauge is very small for even one motor driver, especially through 100 feet (50 feet each way). You could easily be losing several volts per amp that you’re trying to draw, so your results are not surprising. You should easily be able to verify your cable’s effect by doing things like trying one motor controller at a time and trying shorter tethers.

- Jan

If this is the problem would we need to completely replace our tether?
Oh, it is not 24 gauge throughout the entire tether, I just realized, most of it is 22 gauge. I don’t know how much difference that would make. There are some sections at the beginning of the tether and the end that are 24 gauge.


Your tether is unlikely to work at all. Can’t you just get some wires of different sizes and lengths and see how much of a drop you’re getting across them?

- Jan

Last year we were driving motors controlled with direct switches over CAT5e and we didn’t lose any power over the 50 ft. Do motor controllers require something different?

Cat5 cable can have 0.2 ohm/m according to Wikipedia, which is 6 ohms over the entire cable length. That will tell you approximately how many Volts you will lose per Amp of current. So if you were driving 1 motor at 200 mA before, you might have had a 1.2 V loss, which could be acceptable. Now, with 3 TReX controllers, you might be trying to power 9 motors over the same cable (is it still Cat5?) and losing almost all of your voltage. It has nothing to do with whether it’s a motor controller or just a motor - the only issue is how much current you are trying to get down that single wire. There’s pretty much no way it will work with more than a couple of small motors.

Do the TReX controllers work with no motors plugged in? If so, you are definitely drawing too much current. If not, your tether is broken in some other way, but it’s still probably not going to work when you fix it, unless you use bigger wires.

Now we are getting power - the problem was a faulty connection. We have tested the motors now and everything works. We are only running three motors at a time at the most.


hi to all,

i would like to ask is there a way to remotely control maestro 12 in anyway within a 100 meter range. .i mean a way to tether controller from point A which is 100 meter away from maestro 12 using cables. do i need another interface to connect to maestro 12 to make it workable

im doing an ROV project coz now its controlled by a jr 9303 9x2.4 extreme power system brand but i tried only 5 meters underwater. .i want to go further.

pls anyone can help me with this

thanks alot

Hello. TTL Serial is not great at long ranges, but RS-485 is. You could get an RS-485 transceiver for the Maestro that converts its TTL serial signals in to RS-485 and have a similar device on the surface.


thanks for the reply sir david. .

correct me if im wrong with my understanding of what you replied to me:

pc -> usb to rs-485 adapter -> cat5e cable -> rs-485 to micro usb adapter -> maestro 12 servo control

or do i connect rs-485 to ttl directly. . .sorry im newbie with newer technology

my 2nd question to sir is that does pololu have any electronics interface where i can connect my camera too rs-485 thru cat5e cable going to the surface then rs-485 to the lcd monitor

thanks hoping for your positive reply and thanks for the patience of reading and helping me

I didn’t know whether you would have a PC at the surface so some other type of device, so I deliberately kept that part of my advice generic. But if you do have a PC at the surface, then a USB-to-RS485 adapter should work as long as it lets you send and receive arbitrary bytes. I don’t know for sure if it is a good idea to send RS-485 signals over a cat5e cable so you might want to research that some more. Once you get the RS-485 signal to the ROV then you should convert it to TTL-level serial (0-5V), not USB. Sparkfun has some RS-485 products that might work for you.

Unfortunately we don’t sell any products related to cameras, RS-485, or cat5e cables. I recommend that you look around on the web at other ROV projects and see what they did to transmit video. Here’s an example: blog.xkcd.com/2010/11/05/submarines/