Let's Make Robots!

My First Robutt

navigate via IR

Pretty basic following of Frits' awesome 'Start Here' robot.  I bought all the parts from Solarbotics and Robot Shop with a few random things that I forgot from Pololu (like that way too huge speaker that I thought was much smaller when I bought it).  Since it's my first robot the costs are a tad inflated since I didn't have any stuff like wires or resistors or a Picaxe starter kit laying around.  I also didn't include the cost of tape so I guess you can add another $10 or so.

Pretty simple, it wanders around and when it comes to an obstacle he figures out which way is better to go.  I added a couple random behaviors to make it seem more interesting.  First off I noticed that he was getting stuck when he ran into a wall or other tight spot (couldn't turn around), so now he tries to turn himself around three times before backing up and doing a 180 (playing an annoying sound before he does that).  Also if he is moving straight for long enough (doesn't encounter an obstacle) he'll look around and go towards the closest thing he can find.

I've noticed that the IR sensor isn't the most accurate thing in the world and I'm not quite sure what to do with the numbers it gives me.  I found some stuff on how to convert an SRF05's values to in/cm but not so much for the Sharp which seems to return higher values the closer it is to something.  Not sure, that or maybe I have it hooked up in reverse or something weird like that.  It's also not very good with seeing stuff above or below it, so he can get stuck in odd places (for example conditions are just right for him to get stuck at the overhang of my kitchen cabinets).

He's also a tad slow, which is I guess due to only 4.5V powering the whole thing and the voltage drop over the L293? (I'm pretty new to this electronics stuff, haven't really done much with it since college, and that was all logic circuits, not electrical stuff).  I think separate power sources for motors and the rest of the thing would be a good start.

Either way it was a pretty fun project and I've already ordered some more stuff including more powerful motors, tracks, some line sensors an SRF05 and a few other random items.  Not entirely sure what I'm going to cook up just yet but it'll be fun to make!

Don't get too attached to him because he's going to be looted for parts in short order!

Start Here Bot lives on in the hearts of us all, but tragically he lost his brains during a transplant operation. He will be missed! However lessons learned from this brave soul will be carried over to future generations of robutts! Let us all enjoy a moment of silence for our fallen friend.

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You don't want those wires hanging loose so tuck them inside your Robutt.


You will be very happy for the SRF05, it is much better than the Sharp! So you will be able to do much better coding!

Remember to use the command servopos, over servo, especially when introducing the SRF05, because you will make the Picaxe count pulses in, while sending pulses out, and that is just on the limit of what it can do steady, so the servo might jitter, but you will have fun figuring that out :)

The Sharp is not liniar; It is not like something this close returns that value, then that value must mean this distance; The graph is curved. And when something is closer than 10 CM's, it thinks it is further away. it works on 10-80 cms only.

Suggestion; Stealth/ouse mode: Make it follow the wall, like a mouse.

Hi Mike, welcome.

That (giant) speaker just screams "Video!" You would do Frits a big favor. I hope you are not burning your speaker. Read up on that circuit. Consider replacing that resistor with a capacitor (ca 10 uF).

About the Sharp: you are correct. The closer the object, the higher the voltage. Except for objects that are extremely close. They give low voltages again. That's why the absolute front of the bot is not the perfect spot to place the sensor.

You are also right about te under powered motors. The driver (H bridge) snips off about 1.4 Volt.

Eep, I didn't even think about the resistor messing up the speaker.  Is there a good kind of basic guide for this kind of stuff?  Like I said I've never really dealt with circuits before so unless there are some specific instructions I am just kind of guessing, which is probably a terrible idea.  I actually had the sharp hooked up wrong for a while such that it wasn't really giving me any sort of meaningful readings and I finally figured out what I was doing but it took way too long.  I need to be super careful with the SR05 because I hear those are really easy to burn out.

Haha thanks, very informative :D


Looks like it was fun to make. I was running into that "having to start from absolute scratch" problem also. Had to make a trip to my grandpa's. He was able to get me started with all the basics that he had scattered around his shop.