Klein Bot

Kleins, robots, electricity

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Jan 2011 Robotz Meeting

Posted by Klein on February 1, 2011 at 10:57 PM Comments comments (0)

Hey, it's been a long while, Christmas is past and good progress has been made on the home remodeling, so I'm back to posting a bit here and there. Tonight I'm sharing a few pics from the most recent local hobby robot club meeting and a new Arduino class hosted by Joe ( http://www.smileymicros.com ). Go check out the photo gallery.

Countdown: 57 hours

Posted by Klein on October 20, 2010 at 8:52 PM Comments comments (0)

Octowobble was nowhere near ready for his coming out at the local robot club last night, so he's being schooled on the workbench tonight. It may be a late one -- he's been very bad.


I did get some good tips on things to try.The best route was to switch from "simple anti-phase PWM" to sign and direction control.


With anti-phase PWM, you peg the PWM ("speed") pin high, and alternate the direction pin quickly. If it's forward half the time and back the other, the net power to the motor is zero. As the PWM balance shifts, so does the average power and the motor turns. The theory is that the ~500 Hz PWM from the Arduino is insufficient to properly drive the input pin.


I've switched a driver to sign and direction. This is an easy change, just un-tied the PWM from V+ and brought it out to an Arduino pin. I'm tweaking the software and testing is about to begin.


Update:

Did you know that if you comment out code, it doesn't run? For instance, if the code that actually writes to the motor driver pins is commented out and replaced with Serial.print commands, then the motors never actually turn, and there might actually be nothing wrong with the driver.


Further Update:

It works! I'm now switching to work on the beacon detector. I can't rely on their beacon since I've never had a chance to test against it, so I'm cobbling together one of my own.

Countdown: 104 hours

Posted by Klein on October 18, 2010 at 11:42 PM Comments comments (0)

I'm trying to squeeze in some functionality before the local robot meeting tomorrow night.


Current status: I've discovered that the twin motor driver board doesn't drive one motor well when both motors are connected. Short? E-m interference? Time for some more troubleshooting.


Update:

I thought this might be a quick fix, so I played the "just a little more, I've almost got it" game. I checked the datasheet "typical application" notes and updated some component values and tied an output pin high. But somewhere in the changes, I broke one of the drivers. Now it's 2 AM, and there's no sleeping in tomorrow. Maybe I can find a quick fix before the robot meet?


Off to bed.

Good news, bad news

Posted by Klein on September 22, 2010 at 8:11 PM Comments comments (0)

There was a lot of building going on Monday night (9/20). The metal body has been cut and formed, and components have been fit on. I only got some little bolts tonight (Wednesday), so it's just held together with big twist ties right now. I'm basically happy with the layout so far. I think it's pretty; Ben wants to paint it purple with different colored stripes ...


The big set-back Monday night was the smoking of the motor driver board. It was 2:30 AM, so I took that as a sign that I should go to bed. I'm not sure what the cause was -- too much power or floating logic inputs, just don't know. I've still got the original Roomba board, so I'll scavenge the power transistors off of that and put them into an h-bridge circuit I found on Chuck McManis' site. The transistors should work, since they drove those motors before.


McManis H-Bridge link


There was no building last night, as we were presenting Octowobble to the Knoxville Area Robot Group. I was hoping to have a moving demo, but I couldn't get the magic smoke back in the motor driver in time. The next meeting is the week before Robot Rally, and I hope to be making only minor adjustments by then. Wish us luck. And come check it out then.


Knox Area Robotics Group link