Monday, October 19, 2009

And the Lord God formed man of the slime of the earth: and breathed into his face the breath of life, and man became a living soul

I finally managed to properly assemble my build platform. The frame is made out of aluminium profile. There's a company around that sells and cuts it to size. Pretty cool stuff to work with. I'd say this is like LEGO for engineers (engineers, not adults:).

At the top left corner you can see a bearing unit. I'm planning on putting the ball screw through it. But at the moment that's still in transit. Plus I need to get its ends machined somewhere.

Saturday, October 10, 2009

Rail, first try

Now that I have drills and stuff I can make some proper holes. And this is the first result. The printing head mounted onto rails.

This video shows it "working". I have yet to construct a platform to mount it to and also I lack the means to propel it back and forth. I'm planning on using a lead screw.

Bench drill

A week ago I tryed to make a hole into a thicker aluminium piece with my makita hand drill. And. I failed spectacularly. The hole was not straight enough so that once I mounted the detail to a motor axel it was just wobbling all over the place.

So I decided to get a bench drill. Most probably a slight overkill but will be useful. Here it is. Optimum's Quantum B14: 350W, 520-2620 RPM.

Friday, October 9, 2009

Tool rack

It could be I'm a tad crazy. But I decided to get a tool panel. Here it is:

Friday, October 2, 2009

Playing with a DC motor

So I got the DC motor yesterday and all the chips to run it with.

Here's my setup with the motor:

The motor is a 4.5-15V up to 22W with a 750:1 gear reduction. But it seems I got the wrong motor. You see I mixed up RPM and RPS in my head for some reason. Haven't worked with motors before so.. But still pretty embarrassing. Don't tell anyone.

I'm using a RECOM R-785.0-0.5 DC/DC converter to make 5V for the logic chips out of the supply voltage (works in wide range so good for my testing).

Motor is run using an Allegro 3953 full-bridge PWM DC motor driver. One thing to note here is that I burned my first chip at motor braking testing, probably because I didn't bother to properly setup the sensing pin. Then again I haven't dared to retry braking using my second and currently only chip. There was some smoke, panic and excitement. Fortunately it seems nothing else burned.

And everything is controlled with an ATMEGA48 microcontroller. I moved on to using its PWM functionality (instead of the inbuilt PWM of the Allegro) to modulate the motor.

Now I've been playing with this motor here to get an idea how it works but found another way to play it. Forgive the pun. Here's a video:

Basically, when doing very high frequency PWM the shaft inside the motor tends to just vibrate. Here's a better melody, a known tune by Beatles: