RoboBrrd: Three Bad Things

Posted by Erin, the RobotGrrl on Saturday, April 9th, 2011

I like to think of robotics as the art of trying to accomplish something despite the numerous things that don’t work. Last week, before heading off to GTR, I made an effort to try to get a RoboBrrd video done. It didn’t happen, because there was a crazy number of things that didn’t work.

I tried to use the TLC5940 chip that also controls RoboBrrd’s eyes to control the servos. It was hard to set up because there had to be many short wires attached to places that already had a lot of wires attached. I used two LiPo’s in series as the battery, for a total of 7.4V. Some of the servos were working, some were acting funny. I added in a 10uF capacitor to see if filtering the voltage would help. One of the servos stopped working… I wondered why, and read the product’s specs (this is probably best done BEFORE you start to do anything with the product). They are only rated for 6V!

The TLC5940 was sloppy at controlling the servos anyway, so I decided to go with the servo library. At this point, I also needed a voltage regulator to bring down the voltage to 5V. I got the LM317, and prototyped it on a breadboard first. It seemed to work okay, so I soldered it onto the protoboard. Once I plugged in a servo, the voltage would drop down to 2V, and the servo wouldn’t move. After much help with the kind people in irc.freenode.net#fmcg, we deduced that I used the wrong pinout for the plastic package. See, the old guy at the electronics store printed out the first page of the LM317 datasheet and kindly drew on it the pinout. The pinout he gave was wrong.

Once the LM317 issue was fixed, it was getting extremely hot. This was quickly and easily fixed with a giant heatsink.

The final issue was encountered during the Robot Party on Thursday. There’s some sort of conflict between the TLC5940 library and the servo library. On the higher level, the Tlc.init() function is causing the problem. I haven’t looked into the lower level causes of it yet. Has anyone else had this problem?

The RoboBrrd videos have to start rolling, so I decided to throw in another Arduino to quickly fix the issue. It would be great to find a better solution, though.

You can see the video LIVE on Ask an Engineer tonight! Woohoo!

Or, you can watch it here:

There is still a lot of stuff that I have to do, but we’re at a good place now to start the videos. Here’s a list:
- Add in sensor functionality to RoboBrrd
- Make the base able to move
- Cover the other panels with green felt
- Decorate the base
- Make RoboBrrd #2 so #1 can interact with it (so it won’t be lonely)

When the videos get rolling, that’s when more of the DIY posts will start showing up!

There are a bunch of new photos in the RoboBrrd collection for your viewing pleasure!

This is a really exciting robot, and thanks again to Adafruit for sponsoring all of the electronics. Woot woop!

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License. GO OPEN SOURCE!

Posted in: Adafruit RoboBrrd.

Very old FNRs

Posted by Erin, the RobotGrrl on Wednesday, May 6th, 2009

Something relatively bad happened a while ago to MANOI’s knee servo. All of a sudden it would start to squeal, and the flexibility was down quite a bit.

I didn’t think much of it at the time, but I adjusted the home position of that servo so that it wouldn’t be extenuating itself so much!

It worked fine for a few weeks, then when I was playing with it one day… SMOKE!! I seriously ripped the battery out of MANOI (Adam can verify this hahaha). It wasn’t coming from the Sanguino, SSC-32, or battery. It did seem to be coming from the knee at the time.

BLERG!

And so, MANOI gets its leg dislocated again…

I have a little problem with these things called Japanese screws:

The back of the servo was easy to get off. The insides are impressive!

So, finally I get the screw out:

And it reveals what is inside!

Here is the problem:

Amazingly weird and gross, right? I suppose what happened was the grease got so hot that it melted the gear (smoke) and then when it cooled, it destroyed the teeth. I tried to wash it out, but there’s no way that the gear could return to its initial state.

This problem isn’t too bad– there is an easy solution (woohoo!)- there is a replacement gearset for the servo here for about $4!

Another mystery solved!

Posted in: MANOI, Projects, Robot.

MANOI’s Last Tune-up (Servos)

Posted by Erin, the RobotGrrl on Tuesday, March 3rd, 2009

The servo extension cables from RobotShop USA arrived sometime! I’m not sure exactly when, because I don’t check my snail mail every day… heh!

Oh yeah… if RobotShop reads my blog… thank you for sending all of the ridiculous amount of styrofoam squiggles. You could have used an insulated envelope, but no… squiggles! Hahahaha =)

Hopefully this will be MANOI’s last tune-up! Then I will have to start thinking about the battery… RoboGames is quickly approaching!! (Which means I’ll also have to start thinking about fundraising as well! (it won’t be too bad, about 1/2 the price of the Stanford trip I wager!))

One of the main flaws of MANOI was all of there servo connections… it just was not good!

The way I originally laid out the board was that one side would be for the legs, one side would be for the arms. I am still keeping it this way. This is what it looked like after the leg side was redone:

This is the arm side:

All in all, much more neat. I eliminated the clumsy extension cables that I had before. Look at how much nicer it is!

I am extremely pleased. I used one of the servo extensions for RX and Ground for the SSC-32. This way they won’t keep falling out and bending pins.

In my opinion, there is even room for an Arduino Pro Mini in there now, and MANOI would have hardly any bulk on its back. I did not test the servos yet, nor did I test the skating motions. (I had to go to class) I’m interested to see how the center of gravity changed.

Maybe putting an Arduino pro mini in there would be a good idea… and just have right-angle headers on it, with jumpers going to the wave shield. I think that would be efficient! Hmm!! Exciting!

Posted in: MANOI, Projects, Robot.

RBBBs and Pololu SSCs

Posted by Erin, the RobotGrrl on Tuesday, August 5th, 2008

I received the two RBBB’s, 1 FTDI TTL USB cable, and two Pololu Serial Servo Controllers (SSC) I bought a few weeks ago. Since then… I’ve been tinkering with them quite a bunch. I learned an incredible amount too from just a tiny board!

Building up the RBBB wasn’t too hard. At first, I printed off the wrong ‘instructions’ – which mind boggled me a bit until I noticed that they were indeed wrong. Once I had the right instructions printed… it was more simple. I was worried about the polarity of the bigger capacitors. After I had it all finished… I went and looked up the FTDI-USB cable specs. This cable is pretty interesting if you think about it, 1 wire turns into 6 more colourful wires -Gnd, CTS (clear to send), +5V, TX, RX, RTS (request to send). I downloaded the Blink program without any problems… until I wanted to test it. The LED wasn’t blinking! After about 5 minutes of intense thought, I realized that there was no LED on pin 13. That was a stupid mistake!

Another stupid mistake, but this one is funnier, was when I was trying to test the other RBBB.
… I forgot to put the chip into the IC socket. =D That really made me ‘lol’ for 10 minutes.

Then, I was trying to fit it into the breadboard… lets just say it took a longer than normal time.

When the Pololu SSCs showed up, I was pretty excited! Then when I saw them… they are REALLY tiny! It was a big challenge to solder these without them flying out of my hand. I don’t have a 3rd hand tool to hold it steady, so I would sometimes have to hold the ‘pinchy-things’ with my elbow and hold the solder and soldering iron with my hands. The headers were extremely difficult too…

Getting the Pololu to work with the Arduino is pretty aggrivating. I think I’m almost there, I just have to switch the input to the logic level side as I was using the RS-232 one. I thought that the Arduino used RS-232 on its TX line, but it doesn’t. It uses a non-inverted logic level (er well, that’s at least what I read). Tomorrow I plan on looking up the difference between the two

Here are some pictures… I finally threw the desoldering pump out the window (joking) and bought solder wick. Also finally bought NON-LEAD SOLDER! =D

Other than playing with these, I’ve been flow-charting A LOT of AI programs, and learning more first-order predicate logic. I really like logic and the probabilities and Bayes and everything!!!!! Also having fun thinking about random and bell curves… More back-dated Stanford blog posts to come (so many photos hahah)!

Posted in: Programming, Projects, Robot.

Arduino LED Testing

Posted by Erin, the RobotGrrl on Saturday, November 3rd, 2007

I received my Arduino starter kit from ladyada.com not too long ago – Oct. 30th to be exact – It’s AWESOME! I really think this will work well. Check out the pics and video below!

This is the Arduino Deicemilia board – the main thing.

The Arduino hooked up with a servo – I was testing it. Works well!

This is the protosheild. It sheilds the Arduino for you, this way nothing should happen to it! It is also easier to create circuits with. I spent an hour or so today soldering it all together ^_^ (I learned how to solder, YAY!)

And now for the test video!

Hope you like!

As for the programming of the project, it is not going too well. I will have to devise a new plan ASAP. I believe I have to submit the project near the end of December… YIKES! However, I am sure I will get it done!

I have registered for MIT ESP’s Splash 2007, mainly in Computer Science classes. It’s going to be the best weekend EVERR! I really can’t wait. Hopefully they can help out once I tell them about the project.

Adios amigos!

Posted in: Programming, Projects, Robot.