Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Magnum on August 05, 2008, 02:12:58 AM

Title: trouble in Voltage drop!!
Post by: Magnum on August 05, 2008, 02:12:58 AM

hi, i have a motor driver 6-16V, 15A continuous, and a 12V motor, but the motor is 100m from the motor driver for application. From  http://www.powerstream.com/Wire_Size.htm, i find that if i use 18AWG cable to connect the motor to the motor driver, it can cause 9V voltage drop. besides, the cable can overcome 2.3A only, then it is a waste of the high current motor driver. So do any one can give me some opinion to solve this problem? anyway,  i really don't want to use a cable with large diameter..

Title: Re: trouble in Voltage drop!!
Post by: bens on August 05, 2008, 02:24:06 AM

What keeps you from moving the motor driver closer to the motor?

Title: Re: trouble in Voltage drop!!
Post by: Magnum on August 05, 2008, 02:28:35 AM

it is not i want because the robot should be as small as possible(in fact it has a motor only)..

Title: Re: trouble in Voltage drop!!
Post by: bens on August 05, 2008, 02:43:18 AM

How critical is this constraint?  Can you elaborate more on your robot and why it needs to be so compact?  Transmitting large direct currents over 200m of cable sounds like a bad idea...

Title: Re: trouble in Voltage drop!!
Post by: dsheller on August 05, 2008, 03:33:05 AM

I agree with the above, attempting to transmit that much current over a long distance at such a low voltage is just going to be a bad idea.

Title: Re: trouble in Voltage drop!!
Post by: izua on August 05, 2008, 04:34:02 AM

Use a superconductor. I saw one in a Siberian shop that was working at room temperature.

Title: Re: trouble in Voltage drop!!
Post by: dsheller on August 05, 2008, 05:09:07 AM

Is room temperature in siberia somewhere around 15 Kelvin?  ;)

Title: Re: trouble in Voltage drop!!
Post by: Magnum on August 05, 2008, 05:17:58 AM

the robot is to inspect pipe, so i want keep it as small as possible. In fact i have another motor driver which can overcome up to 30V, but the cable still cannot overcome high current. So do you have any idea?

Title: Re: trouble in Voltage drop!!
Post by: bens on August 05, 2008, 12:08:40 PM

What is the diameter of the pipe you are inspecting?  I think you need to come up with a more innovative mechanical solution that will allow your robot to carry its own battery and driver, or use a motor that takes far less current.

- Ben

Title: Re: trouble in Voltage drop!!
Post by: slo on August 07, 2008, 11:02:47 PM

Use that 18AWG 100meter cable to carry mains AC.  Use fast acting inline GFCI breaker 10A or lower so that you don't blow your clients house fuses in case of a short.  Attach your motor controller, transformer and rectifier to a small 'trailer' dragged behind your robot by a flexible strain relieved cable.  Waterproof everything.  Good luck.