00345 Son of rake robot - laserbot!

He draws on walls using only the finest proton beams:

New patterns imminent. Keep 'em peeled.

00268 Make

The eggs, the pooh sticks, the rake art, the KAP group and the robot that will one day draw in sand have now all appeared in the MAKE blog. I so love their magazine, what a nice vibe to think we are all singing from the same made-up hymn sheet.

Next up will be trying to trigger a Nikon D50 from a PICAXE chip - harder than it looks, as I'm finding out. The result will be (hopefully), some really neat time-lapse photography and possibly even the burst KAP rig (where the camera takes a sequence of images really quickly when I press a button). The collest thing about the time-lapse thing and the PICAXE could be the possibility of having a tracking panning camera doing fully moving time-lapse - a sort of time-lapse motion control. Come to think of it, repeated time lapse moves would look really neat running next to each other.

BTW, I found a couple of old eggs that I hadn't posted:

Although technically speaking there is no egg in the last one.

00264 Pre-programmed robot

So I made a new robot and this time it's got these dual-in-line (DIL) switches. Basically it means that by using different combinations of switches I can call up a particular routine (or pattern) and then execute it by pressing the red button. What it really means is that I don't have to keep going back to the computer to change the settings of a particular pattern to try out different types, I can just load it up with a whole lot of patterns and see what they all look like. This'll make it easier and more productive (?) when I take it to a beach.
I can only take pictures of the patterns at night, so progress is slow, but I'm quite pleased with the offset spiral below. Not perfect, but came out reasonably well and almost as expected.

The idea, although the offset spiral doesn't show it too well, is that one colour of LEDs traces straight lines and another traces the curves/turns. I'm probably going back to the multicolour LED for now, seeing as it doesn't help me to envisage what the patterns would look like on the sand.

00263 Appeal

So after the spirographic robot patterns thing appeared in the Make Blog, I'm appealing to anyone savvy (knowledgeable) enough to recommend a dummies guide to attaching two 14v drill motors to the PICAXE chip. The idea is to run the robot off a motorbike battery (or similar) so that I can generate enough power to leave decent imprints in the sand. I'm imagining two full bridge chips like these, one for each motor and I'm assuming that the PICAXE will generate enough of a signal from an output channel to control the full bridge chips. Then I'm assuming that the Full bridge chips will be able to handle between 10V and 20V to drive the drill motors. I'm such a novice, I guess I'm just hoping that I won't burn anything out, or worse, that I'll solder it all together and nothing will happen.

The previous idea of leaving one enormous pattern hasn't been completely ditched, but has been replaced by the concept of around 10-20 patterns accessed by using tiny DIL switches attached to the PICAXE inputs, four switches giving 4 factorial (=24) possible input combinations and therefore 24 patterns that I can call up on demand. Take the robot to the beach and let it draw numerous, maybe interlocking patterns and then KAPing them like I did with the rake art.

To do the KAPing I need POWER to make a really decent impression in the sand by dragging a rake/plough shaped object behind or underneath the robot. Your input would be most excellent and there would be much love (although I am married, so there might be some love-limits).

Don't even mention the possibility of PICAXE powered pooh sticks

00261 Further developments

This is the latest installment of the robot stuff for making patterns in the sand. So I managed to get the motors of the robot to run at different speeds in order to do smooth curves. It makes things a bit easier in a way. Describing curves is possible by looking at it as line segments, but waaaaaay easier if you can incrementally adjust the motor speed settings. Here's the latest offering, a 760 second exposure - it's certainly a little more interesting:

And here's the perpetrator, or as I'm calling it "The Perpetrator":

The servo will be for lowering the stick/rake/device onto the sand. Yes, even I think that it might not work quite perfectly. Perhaps the trick will be to cause as much disruption to the surface of the sand with the least mechanical effort, so as not to strain motors and waste batteries. The real knack will be in doing a pattern which will be photographable (even I don't know if that a real word, my spell checker says it's not - blaaaaaaaaaah).

And here's the code for the PICAXE:

let w1 = 3000 'forwards length
let w2 = 4000 'pulse width
let w3 = 120 'turn period (via for...next loop)
high 0

check: let b1 = pins
if b1 = 000010 then
low 0
pause 2000
goto main
end if
goto check

main:
high 4 high 7 'forwards
pause w1
high 4
for w0 = 1 to w3 'turn
pulsout 7,w2
pause w0
next w0
low 4 low 7 'stop turning
goto main

I'm so inefficient at programming, but it gets the job done, so hey.

D'you know, I almost forgot to say that the coolest and smallest thing on this robot is the RGB LED - how else would I get multicolour light lines for 50p?

00260 Robot patterns

So the new robot, with two motors (pictures to follow soon) is programmed and creating some simple patterns. To get an idea of how they would look, I used a long exposure (around 76 seconds for the spiral). Real bummer having to wait until dark 'till I could take them.



The spiral would work well if there were loads of them all over the sand, especially if I could do a double spiral, starting in the center of one and ending in the center of the other to give a kind of "figure 8" look.

As soon as I've figured out whether or not I can control the motor speeds, I might be able to form some more complicated patterns.

00257 Robot parts arrive

I've just taken possession of a PICAXE chip and starter kit:

And set to work making a robot with any bits available. In this case I've added a motor and a a servo:

It works OK, but I think it'll go better with two motors (in the post) and even better with two 14v drill motors. The latter will need alot of forward planning and I'll probably have to buy a unit to cope with the increased voltage needed to drive the bigger motors. Then I'll be able to stick a motorbike battery on board and get down to the beach for some cyber-raking action.

I'll also consider attaching an LED to the 'bot in the meantime and do a long exposure of it moving in the dark to see how the movements over the sand might turn out.