Let's Make Robots!

Little 8

fritsl's picture
Very cheap but fun little beginners robot. It think' it has a brains within a Picaxe 8
Cost to build: 
$40
Time to build: 
5 hours
Weight: 
75 grams

Edit: Check out this nice clone: http://letsmakerobots.com/node/8386


From building big, nasty, with large shovel, 2 cores, multiple sensors, soundsystem etc, I got tired of that.. and decided to see what fun I could have with a little Picaxe 8 on a board ($16, total prize for robot is about $40).

Version II of this fella here: http://letsmakerobots.com/node/101

I have since recieved some interest in how to build this extremely easy and cheap robot, and so I hereby transform this post to a small and simple tutorial:


Shopping list:

Can be bought from Picaxe:

You can get this from anywhere:

  • 1 9V battery
  • Some sticks and something to cut them
  • Screwdriver
  • Soldering iron and led
  • Some pieces of wire and something to cut it with
  • Some different types of glue or tape etc
  • a table-tennis ball and a knife to cut it
- And then you need some motors with wheels. I recomend these, used in my robot.

 


I like the challenge of only having 8 pins and 128 bytes of code etc. But be aware; you get a funny robot, but it is blind, can only sense a bumper in front, and you really do not have much memory in it etc.

What I did after building this, was i set it up with Easy Radio serial wireless input on the only pin left for anything. This made it possible to control this little robot by another robot, which opens new windows etc.

Some friends and i in our local club also had a contest of making it draw the number 8 on a piece of paper with a marker glued to its back.. Good fun little fast and chep robot!

 

IMG_3399.jpg
A stick, some switches, and a sliced up table-tennis-sized ball for "the third wheel"

 

IMG_3397.jpg
To get the 9V down to 5V, I use a voltage regulator.

IMG_3400.jpg
I was just mounting with some glue, the strips just tohold things in place..

IMG_3401_0.jpg

IMG_3403.jpg
An angle grinder may look like an extreme tool for such a small job - but I use it quite often. Just turn it on, hold it steady against something, and anything you stick in there is just vanishing, nice and smooth - compared to cutting such small parts. I also use it for acrylic (Plexiglass), again it is perfect to make little cuts and markings.

IMG_3414.jpg

Just follow the instructions that comes with the board - it cannot be more simple, hook up the 2 motors.

The motors I recomend are incredible! Fast and strong, even though I only feed them 3.5V due to the 1.5V drop from the Motor Driver. So I actually had to make a "tale-bumper" (red square) as it was lifting the front a little too much :D With the bumper on it turned out quite cool, as it is just as capable of navigating on only the rear-wheels.. there is nothing else but a glider in front anyway.

IMG_3406.jpg

All needed now is some code and the battery.

TIP: Get rechargeable batteries (and a recharger) - Or you will soon have used as much on batteries as on the Robot itself!

REMEMBER: If you make anything like this, to take a picture and show me :)

Here is the code used in the robot on the video. Don't mind that the names of the sub-routines does not make sense to you. Fact is that nothing in this code makes much sense, it was just the fun I had at the time when I shoot the video :)

I will have a closer look at this soon, but on request, here the code from the video:


symbol fw = 20
symbol bc = 200

b0= 175

''''''

dav:
random w5

for w3 = 0 to w5
if pin3 = 1 then
gosub bum
end if
next w3


b0= b0 +1
random w5
if b0 < w5 then goto hest

random w5
if w5 > fw then
high 1 low 0'ForwardRight
endif

random w5
if w5 > fw then
high 4 low 2'ForwardLeft
endif

hest:

random w5
if w5 > bc then
high 2 low 4'ReverseLeft
endif

random w5
if w5 > bc then
high 0 low 1'ReverseRight
endif

goto dav

bum:
w4 = 32212
return

high 2 low 4 high 0 low 1'Reverse
pause 300
if b0 > 175 then
high 1 low 0'ForwardRight
high 2 low 4'ReverseLeft
else
high 4 low 2'ForwardLeft
high 0 low 1'ReverseRight
end if
pause 300

b0 = 175
return

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The_Black_Cat's picture

Nice Robot fritsl 

 

 

 

samdaman's picture

I have one last (hopefully) question. I apologize in advance for asking it, because it's probably a lot simpler than I'm making it out to be.

Anyway, I can't figure out how to flip the switch of the PICAXE board the one that says "PROG" and "RUN."

If someone could help me with this I would greatly appreciate  it, and would possibly have the little thing running today.

ignoblegnome's picture

It's a jumper, not a switch. Although you can wire in a cable to a remote switch.

If you connect the jumper across one set of pins, it lets you program the Picaxe. If you set the jumper the other way, you can use Output 0.

 

 

ROVguy's picture

I like the little one!

Though it might need to stay off the caffeine.

Hello

I have one question about this robot. This motors I can drive with pwm? Which frequence is good choose for this motor?

 

Thanks for help.

 Samo from Slovenia

fritsl's picture
I dont understand the question. You can drive all motors with PWM, that is just turning on and off the motor really fast.

Hello

I have one question about this robot. This motors I can drive with pwm? Which frequence is good choose for this motor?

 

Thanks for help.

 Samo form Slovenia

I used this picaxe 8 board befor and it worked fine. now i tryed it and the motors run all the time unless its downloading. also u would never have to take it out of the program jumper mode becuase it works in it. HELP
fritsl's picture
I dont understand you, sorry.

Little 8 is a fast robot. I am starting to think about building that robot. I do have a quick question.

Does the switches from radio shack work?

SPDT Switch Without Roller<----
SPDT Switch with 3/4<----

Even though their not long whiskers like from your robot, but do they still work for the 8pin motor driver board?

samdaman's picture
I'mm trying to get to the link for the bumper switches, but these links aren't working. Can you help.
rik's picture
That link is an old e-bay sale. So it's expired by now. Did you try  google instead? These switches are very basic. Any robot-parts webshop sells them. Or any generic electronics store.
Jonny's picture

Does the  picaxe 8 boared has a motor driver built in it

 

jklug80's picture
There is a slot for a longer chip on the board. If it says l293d that is a motor driver. It MAY have a darlington which allows you to use 2 different voltages. See what is written on the chip and google it.
Jonny's picture
yes I can do my plan then
Jonny's picture
does it matter if u have a 5v regulator or not acording to your code
jklug80's picture
Code does not care what voltage is supplying the picaxe. The picaxe cares what the voltage is. Too low and it won't work, too high and POOF!
Jonny's picture
If i used diffrent type of motor could I still use this code
jklug80's picture
Code isnt really motor dependant. If you use different motors it will just make the robot move faster or slower.
1220's picture
thanks
1220's picture

i couldnt find them at radio shack

 

 

jklug80's picture
That's where I get them all the time. Did you ask or look in the drawers with all the LEDs, switches, resistors, etc?
1220's picture

were can I get those bumper switches

 

jklug80's picture

radioshack or any other place that sells electronic components

 

bananas's picture

I'm new to the site. I have built a model of little 8, but i named it zingo.I just gave it new batteries but now it goes to fast.How do I slow it down?

ignoblegnome's picture

Are you driving the motors with 9V directly or using a 5V regulator as fritzl suggests?

What motors are you using? Are they geared? What gear ratio?

jklug80's picture
Reduce the voltage or gear the motors.
1220's picture

yea i realized i jumped into robots too fast without any knowlage on how they work, if my ideas will work for sure, ect.

1220's picture
actualy i found out that will not work so scew the robo cop name haha. the reason im commenting again is that i do not know exactly how to hook up the bumber swithces like you did. i have some similar and i saw your illistration in that comment but it did not make much sense to me. im a beginner and 13 yrs so thats why i dont catch on to things good. plz anyone help me out and describe it like your telling a 2nd grader how to do it :)
fritsl's picture

You should start simpler, you are trying too many things at the same time. It is very common.

Start by making an LED blink, and only that. Make variations, and then move on, and make sure you master the next thing, and only move on once you master what you do and find no more challenges in it.

1220's picture
hey frits! i have ordered the parts for this little robot and i was wondering if there is any way to put on red and blue LEDs on him. the link for those bumper switches are broken for me so ive been searching fo hours for those things. any other site that has those? also the usb cable link is broken and i coudnt find any info on one that would work. I need help plz!
fritsl's picture
I am sorry, but to put it short; These are the litte things that you have to find out yourself.
EEEEE's picture
Hey I was just wondering in the videos how come the robot moves backwards after it hits something and then turns around? why doesnt it turn around right after it hits ? Is it the way the code was written ?
fritsl's picture
Yes, it is how the code is written

Hello, I'm tring to make this robot for a Technology projct, and I was wondering if u can explane sum stuff bout the codes. and how to make it?

Blshook

fritsl's picture
You should read the manuals for the language.

Hey there cool robot. i was wondering if could use this cable (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&Item=350222968722&Category=40059&_trkparms=algo%3DLVI%26its%3DI%26otn%3D2) instead of the one you suggest. It looks the same. if not this one can i use the picaxe serial?

 

Another thing can i use alternative motors?

 

regards

 

ignoblegnome's picture
The Picaxe cable has a circuit in the USB connector head. It is not just translating the pins from USB to serial. So I wouldn't trust that the cable you listed would work with a Picaxe.

ok thank you both 4 your answers

 

fritsl's picture

Sorry, I would not know about the cable.

You can use the moters that you would like, of course. Just make sure they are geared!

So i copied the code into the program editor. I switched the jumper back to run. the bot will drive forward but when it hit the switches nothing happens. I dont know why but if i take out the return command after the w4= 32212 the switches will activate and the robot will spin in circles.   Help please   thanks

Hi,

Do anyone one know the dimensions of Little8 platforms?  I'm new to robots and this would be my first one. Also, do anyone know any american websites to puchase the bumpers because i can not find any?  Thanks

fritsl's picture

I dont know about shops, maybe sparkfun.

For dimensions, I'd look at

  Datasheet

 

Edit: OMG, there are no dimensions in the datasheet. Sorry, I am no help here ;)

Im wanting to buy all my parts in a bundle from the same website
for this project, so could you advise me on which motor from this
page is most suitable?

http://194.201.138.187/epages/Store.storefront/?ObjectPath=/Shops/Store.TechSupplies/Categories/ElectronicComponents/Motors

Thanks in advance for the help and for this fantastic website, it has
helped me get a foothold in robotics!

fritsl's picture

Sorry, but the motors that I used are quite rare, from solarbotics. The fmous "pager motors", talk of the town everywhere.

Any geared motor will do, as long as you can put a wheel on it. 

But.. None of the motors on the page you are linking to are geared!

Read this: http://letsmakerobots.com/node/763

ok i understand now thanks ^_^
so...uhh... fritsl, do we need to use a wire connector to connect the 9v battery connection to the wire. sorry, im actually new to this website.
one thing that confuse me on building little 8, is about the voltage regulater, i mean that i didnt really get the instruction. Do u have to try to stick the wire in the 5v 7805 voltage ragulater like thru the wires.
robologist's picture
From the link above, check this circuit.