Let's Make Robots!

First Robot/ BarkTrack

Navigate around via ultrasound, barks when someone knocks on the door.

Hi All,


I’m new here and first off I want to say what a fantastic site this is. It’s certainly inspired me to build my first robot, which is going to be based on the start here robot. I’m new to all this and have no experience of robotics, electronics, or programming, so any help will be gratefully received.


After viewing this site, I’ve decided to build my robot, at present I have no project board, or any other components, or any money to buy them with for that matter. My first thoughts were to venture into the attic and look for an old RC car, or something like that I could use as a base. Something with a gearbox already in place. Unfortunately, I found no RC car. I did however, find something much better than that. I found my favourite childhood toy, that had not worked for many years. I found my old Bigtrak.


(Does anyone remember Bigtrak? It’s been re-released this year. Yes I’ve bought one.)

So, Bigtrak sadly died many many years ago, so I’ve now stripped out all the old electronics ready for new going in.

The years of storage in the attic have also taken their toll on Bigtrak though. The front axle has snapped in half, the 2 rear axles have snapped off altogether, with one remaining unfound, 2 pieces of body trim are missing,  a thick coating of sticky dust is in all the crevices and the batteries left in the battery box since sometime in the 1980’s have leaked everywhere.

Not to worry though, strip the whole thing down, and after a good clean up, all the sticky dust, the brown battery sludge is all gone and the wife is non the wiser Bigtrak’s been through her dishwasher.

I’ve now repaired Bigtrak’s front axle by screwing a metal plate to it, holding it together. The rear axles were a little harder to fix, especially since one was missing. I found something suitable to replace this with though. I’ve drilled the center of the axles out and used metal pins to hold them to the chassis.

Photos are here, but I can't work out how to put them in this post. I end up with half a photo.

Well, that’s the repair work out of the way. Now to the tricky bit. I intend to mount an SRF05 on a stalk from where Bigtrak’s blue laser cannon used to be. This will allow it to turn in both directions without catching on the bodywork. It will be controlled by a servo mounted in the old 9v battery housing, with a long push rod connecting the sensor to the servo with ball and socket joints at both ends. A miniature servo will have to be used for this, but I see no problem with that.

Bigtrak was originally powered by 4 DD cells and a 9v battery. As mentioned above, the area where the 9v battery used to be, will now house a servo. Where the 4DD cells used to go is a sizable area, especially now I’ve removed the plastic moulding that held the batteries in place. I’m planning on fitting this area with a big 6v rechargeable battery with a regulator to knock it down to 5v.

There is plenty of room within the body to install the electronics. The topside of the body also has a stereo jack port which I’m planning on linking straight to the picaxe board for programming. The motors and gear box are all still working fine, which is a bonus. There is a cut out in the gear box where a board used to fit, for dead reckoning. Maybe I’ll find a use for this sometime, but at the moment I’m just keeping it simple. An interesting thing with the gearbox is each motor has a magnetic fly wheel attached, these keep the motors turning at the same rate allowing bigtrak to always move in a straight line, but don’t prevent the motors from turning in opposite directions.

Well, that’s as far as I’m up to at the moment. Nothing more than a rolling chassis, but with time and when I’ve sorted some cash out I’ll be a roboteer, like the rest of you.

Thanks for reading...   ideas, tips and opinions are always welcome,


The Bromz.



My project board, chips and Picaxe cable have arrived today.

Busy day for me tomorrow. I'll be scratching my head and swearing all day, when I can't figure out what I'm doing.

Hope you guys will be on hand to give me any info I need.

The Bromz.




Ok, so it's not much of a robot at the moment, but it's the first time it's moved in well over 20 years. Once I have some sensors, I'll get them added to it and it should be a whole lot more entertaining.

See video above.


The Bromz.






My SRF05 arrived, so I now have an autonomous Bigtrak! There's still no servo, so the sensor can't look from side to side, but that's for my next shopping trip.

The programming's a little, or maybe a lot shakey, but it's the first thing I've programmed since my bigtrak was new, in the early 80's.

See video.

Let me know what you think guys.


The Bromz



My servo arrived today. It's taken 15 days to arrive, but it did come from Hong Kong.

Anyway, I've attached it to my robot and he's running around all over the house avoiding stuff now. I've still got some tidying up of wires to do and replace some body parts, but it's all working well. I've removed the stalk from the front, that housed the SRF05 and managed to get it mounted on the front of the vehicle. This is allowing it to see smaller objects on the ground.

I've tried programming again and again, but it never does what I want it to, so I've stollen Frits's code. Thanks for putting that up on here for us Frits.

See video and let me know what you think.

I love it!



 Just a few pictures now I've routed the wires nicely.

All I need now is my rechargable battery to fit in the battery compartment and it'll look great.


Thanks for looking


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Wow, a Bigtrak. My buddy's brother had one of those, he wouldn't let us touch it. That's a great Smithsonian hack platform, mate! I look forward to the project.

Is it just me or is anyone else only getting half-pics in the links? 

I could only get half pics when I was trying to put them in my post.

Welcome to LMR. I'm looking forward to seeing this come to life.

Thanks Ignoblegnome. It may take some time, due to financial and time limmitations, but I'll get there... one day.

How to insert images in posts

Plus: scale down the filesize. Those pictures are huge. Three time bigger than my entire laptop screen. We like 'm at max 500x500 pixels. Usually our image uploader will do the scaling for, but your source is so slow, it probably gives up halfway the process. So scale them down yourself.

Thanks Rik.

That should help

To me, that black circular piece on top looks like an awesome spot to mount a sonar sensor. If you can mount a servo inside and have the sensor sweep left and right, it would look just so cool.

That's a good idea. It's probably a lot easier than the linkages I've setup to get the sensor on the front. Think I might be changing my designs. Thanks Ignoblegnome.

WOW! I still have my BigTrak and it still works. If it did not work, I would be inclined to rebuild it with sensors ect...

Good to see an old BigTrak

An update to let you know I've mounted an ultrasonic sensor on my robot. I know it's not an SRF05. It actually comes from a Cybot. I don't know if I'll get it working, but it's worth a try.

Here's a new picture and also a picture of my brand new Bigtrak, for all those of you who have been talking about the origional.


New Bigtrak

All other pictures can be found by clicking here


The Bromz.