Author Topic: $50 Robot LiPo?  (Read 1325 times)

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Offline mrtimbolognaTopic starter

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$50 Robot LiPo?
« on: August 30, 2009, 09:06:55 PM »

I just finished my $50 robot (first robot, first board solder) and I was quite happy to see it chasing my flashlight beam.

2 questions -

1) I am powering the bot with one 7.4V LiPo 900mah I had from R/C. Is there any reason to set it up with an additional 9V to power the servos separately aside from increased run time?

2) I have the bot set up in a computer mouse case, with micro servos and cardboard wheels. All ran pretty smooth at first. Then I thought it would be smart to wrap the cardboard with rubber from an old bike tire for tread. Now, the bot is considerably more twitchy..... still turns towards the light and all, but its really twitchy in it's movements, and it seems like the servos are under a lot more stress too. Could this just be from the increased traction? Could I mess with the programming a little to get it to smooth out? If so, what part would I be looking for?

Thanks ya'll - and big ups to admin for the creation of this site and the $50 bot tutorial.

Offline SmAsH

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Re: $50 Robot LiPo?
« Reply #1 on: August 31, 2009, 12:31:50 AM »
7.4v seems a bit high for the servos, do they ever get hot?
if anything, you should use the 9v for logic (regulated) and 7.4v for servos.
the only reason admin suggested two packs was because of possible "spikes" caused by the servos that might cause resets with the microcontroller.
since then battery technology has improved so much so this is not really needed. the cap also gets rid of this.

if the servos are struggling with the load, there isn't much in the way of software you can do.
if you try just putting rubber bands around the tires, this can help with traction while still not making the load much greater. i would think the servos "jitter" is caused by too much load placed on it, after all its only a micro servo. ;)

Offline Razor Concepts

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Re: $50 Robot LiPo?
« Reply #2 on: August 31, 2009, 01:18:05 AM »
The lipo will have a peak voltage of about 8.4 volts, which is way too high for servos.

Since you have a smaller robot, it will draw less current. You should be fine with running the lipo through a low-dropout regulator, keeping everything at 5 volts.


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