Robot companion

Robot companion 2

I was talking to my Dad this weekend and I gave him a little update on how my robot project is coming along. So here is an update with photos for those who are interested.

I made some major modifications and improvements since the last post. The two largest improvements are with the power supply and cleaning up the Arduino shield connections.

The power supply used to be two separate batteries, one for the computer and another for the drive system. I started out with 4 NiMH 1.2v AA cell batteries for the drive wheels
, and a 9v battery for the logic. This was of course a poor choice due to the low power and low voltage of the 9v battery. A 5v regulator needs at least 7.2v to properly regulate, and the 9v bat runs down quickly. So I uped the power to a single supply of 8 AA size NiMH rechargables. That covers the voltage requirements, and with 2400ah should last quite a while.

I also removed the rather cluttered Aduino shield and replaced it with a wing shield and installed additional 5v and ground terminals. This made the routing and connecting of all the I/O much easier. Speaking of I/O, I added an additional feature. I installed a backlit serial LCD module. It is a really cool little device that allows my little bot to communicate with me without having to use a PC. It also has a little speaker so I can have it beep when appropriate. All this and I only have to sacrifice one output line.

I also took advantage of the encoder outputs on the motor shafts. If I can figure out how to use interrupt routines to call on functions the little bot will be able to track the wheel positions to a high degree of accuracy.

So all in all things are starting to look pretty good. Here are a few photos of the little bot, before I close it up and start programming. I have tested the I/O and everything seems to be connected properly. Not to give it some smarts.

Pf

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3 thoughts on “Robot companion

  1. How long of a run time are you looking for? Full autonomy of movement? Could you replace with line tracking, or simple distance measurement? Dump the Batts, and go with ultra Caps. I love Caps, so many cool thing s to use use caps for. UUUUmmmmm, plasma field generator!

    • I don’t have any estimates for runtime as I don’t expect it to be in constant motion. NiMH batteries were a compromise between Nicad and LYpO batteries; I didn’t consider ultra-caps. Mostly I didn’t want to spend a lot of time recharging batteries. The motors pull between 500-800ma each depending on speed and load, and the logic takes about 100ma to run the Arduino and sensors. With motor encoders on each wheel I should get a good degree of resolution for wheel location, I think about 1024 pulses per wheel rotation which comes to about 9.42” of travel, or 108 pulses per inch. But I don’t expect 100th of an inch accuracy, there is too much variables to consider including slip and rear wheel wobble. I am doing distance measurement, if you look at the photos there are two infrared range finders and one ultrasonic range finder on the front, and one infrared range finder on the ass. The IRrf is good for about 9” and the USrf is good for several feet. I don’t like line following as it is way to application specific.
      -pf

  2. scudrunner says:

    My Arduino addiction is getting out of hand. I have way to much proto board stuff. Been heading into vacum tubes of late. I love the light.

    Date: Mon, 15 Jul 2013 03:42:03 +0000 To: huntermb@aol.com

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