Community Question

I have never blown a board due to being careless, until yesterday...

I am was using an Arduino Mega for gathering information from a Neato XV-11 LIDAR sensor. I had disconnected the power cables and unplugged serial port wiring to mount the board on my control box. After getting the Arduino mounted and plugging in the cables again, I attached the 12v battery. Things went down hill from there.

Sensor readings were not coming back from the LIDAR and I messed around for about 10 minutes trying to figure out why. When I inspected the wiring, I realized that I had plugged the ground wire one spot too far to the right (VIN). The board was already grounded through the 12V plug. The ground wire that was plugged into VIN on accident was plugged into a Beaglebone Black into a ground pin. The BBB wouldn't boot up. The LIDAR was plugged into power on the Arduino along with the serial connections and the other serial connections were going to the BBB.

The BBB looks to have survived the mistake. The Arduino definitely didn't. I don't know about the LIDAR. The EZ-B for this project is still in the box, so it is okay :) Thanks to RobotDoc I have a logic analyzer so I will be able to check the LIDAR to see if it is sending back packets or not shortly.

Long story short... Always double check your wiring, especially on a board that you are not familiar with. It gets easy to get in a hurry and make a stupid mistake costing you money for replacement parts, but more importantly time waiting for the parts to arrive.

On another note, I have a Flashforge Pro 3D printer that I am using for this project. It is a Makerbot 2X knock off. There is one issue that had me stumped for a couple of days. The printer would just start jerking for no reason. I could jog the controls in either X OR Y without any of this jerking happening. Finally, I brought the extruders to the front left corner of the printer and told it to home (which moves the extruders to the back right side of the printer). The jerky activity started about 2/3 of the way back from the front left. This told me that it was nothing with my slicing settings. I then did some looking online and discovered that the X axis stepper motor cable on these printers can develop micro fractures due to repeated bending. These cables are not designed to be bent over and over again. I manufactured a cable and tested this out. It worked without any issues for a while, and then the problem came back. I am sure that the wire I used could have the same issues and probably more so due to me doing this quickly to identify the problem. I pieced some jumper wires together to make this cable. Now I wait for the 4 replacement cables that I ordered.

So, I am waiting until I can continue printing, and I am waiting to be able to continue working on the SLAM parts of Rafiki. Good time for me to check in and make sure that the other development is progressing.

We have decided that the parts of IBM's Watson solution that we were looking at using are not quite up to par with some things we can do ourselves. We have backed off on using Watson for now and are working with Wolfram for the knowledge and information pieces of this project. Unfortunately with a project like Rafiki, you try some things for a while and at some point you have to decide that its not worth it going down the path you have been going down. Time spent but knowledge gained. Knowledge doesn't have a price tag so no problem in my book. We are falling a bit behind but the robot will have more capabilities than I first imagined in the long run.

Have a great day everyone.
CochranRobotics
Commented September 2015
Oh, one more thing. We are using LiFePo4 batteries with this project. So far I am very impressed with how long these guys run. The batteries that we are using are self balancing 12v 20ah batteries. They last a very long time. I have been working on the logic boards (all of them on at one time), along with using the 2 drive motors a lot to get the exact settings for moving robots specific distances, or turning specific degrees and have only had to charge this battery 2 times in the past month. The max draw from this battery is 30 amps. It weighs only 7 lbs. Incredible batteries but cost around $125 per battery. Our goal is to have up to 3 of these in a robot providing an incredibly long run time. The customer will be able to specify how long they want their battery to last between charges, which will determine how many of these batteries will be included. My original estimates of 8 hours on a charge per battery so far appear to be way low. Toymaker told be they were, but, you know how it goes. I had to see it to believe it.
CochranRobotics
Commented September 2015
So true. When you are making progress, it is easy to convince yourself that you just need to work that 10 more minutes. That 10 minutes set me back about 3 days in waiting. Sadly, I can't say that I won't do it again.
fxrtst
Commented September 2015
@dave,
Well
at least you can recharge your own batteries while you wait! Speaking of batteries I've never heard of Life batteries. What is the size of the batteries you are using? Must be somewhat small if you can add up to 3 to a robot!
CochranRobotics
Commented September 2015
7" X 3" X 6.5"

with 3 of them, your talking about a block about 7" X 9" X 6.5". I would expect this to run my robot for around 36 to 72 hours between charges with pretty constant use. It is hard to tell at this point though because not all of the motors and some other components are attached yet. These other components either contain their own batteries or are very low current though so I don't expect there to be much more draw. I wouldn't be surprised if that estimate comes out low.

These batteries stay at 12.8 volts for an incredible amount of time. This is the best I have seen to date for large robot builds based on weight vs performance unless you need to draw a lot of current.



example lifepo4 battery
fxrtst
Commented September 2015
Very very cool. I'll look into these!
Dave Schulpius
Commented September 2015
Been there, don't that. I blew up one of my V3 EZB's that I really needed. I was so pissed at myself. I dragged a hot 12vdc jumper across the digital pins and shorted the whole main chip out. I know better than that. Hell, I routinely handle energized high voltage wires and jumpers for a living and if I had done that on the job I'd be lucky to be typing this right now. My excuse was also like yours; I was tired and in a hurry. It's a hard and embarrassing lesson to learn. You should change your name under your avatar for a week to Sparky. :P
Question
AvatarCochranRobotics
Asked on Tuesday, September 15, 2015