Since I’ve last posted I’ve been up to a number of things with the delta robot. To start with here’s a video of the robot drawing circles:
Since that video was recorded the control electronics have been rebuilt to use an stm32f4 discovery board. The extra processing power this board provided enabled the inverse kinematics to be run on the delta robot rather than on the computer. This smoothed out the movement of the robot and simplified the code to control it on the computer side. Hopefully this will eventually allow me to integrate it nicely into 3rd party 3D printer control programs.
Another area I’ve been playing with is using the delta robot to draw animations using light and long exposure photography. The following video shows the first test I did.
To achieve this a camera running chdk was triggered from the computer using an arduino to capture a long exposure image. As the image was being captured the robot plotted out a 3D shape with an LED attached to its end actuator.
The whole process was scripted using python and repeated multiple times to capture multiple frames.
All the images were then stitched into a single video using ffmpeg.
Here’s a more elaborate animation made using the above technique.
Another quick update to show some progress made this evening. I’ve plugged my inverse kinematics code into a quick and dirty motor controlling serial comms link to the Arduino and can now move the head of the delta robot to arbitrary XYZ coordinates. Here’s a video showing the plotting of slightly misshapen square (need some micro-switches to finished the calibration routine)
I should be able to get some more speed out of it by improving the Arduino comms link (it’s sending individual steps to the motors).
I’ll get around to doing a more descriptive post once I’ve got G-Code interpretation working (all the python code is done, just have to plug the bits together).
Here’s a quick video showing the first movement of the robot:
The video is only short because one of the grips for the toothed belts worked loose and it ended up crashing, fortunately there was no damage.
Laser cut parts and mechanical accessories have all arrived so without further ado here’s the first image of the linear delta robot as it currently stands.
I’m very happy with how it turned out, managed to not make any massive errors in the design and it’s not fallen apart that much since being bolted together. I’ll post more info, the design files, plus a video once it’s started to move.
In other exciting yet totally redundant news I’ve settled on a name for it. It will be called *insert drumroll* the Bakewell Liner Delta Robot. I’ve settled on this name mainly as a homage to the Rostock delta robot from which i took a lot of inspiration.
I’ll be showing off the (hopefully) working robot at MakerFaireMCR on the 28th and 29th of July at the Museum of Science and Industry (MOSI) in Manchester.
The first batch of parts has arrived for the linear delta robot. I’ve chosen to base the electronics around an Arduino and some really neat A4988 stepper motor breakout boards from Pololu. Quite incredible that for such a small package they can deliver a supposed 2A at 35V. They also support up to x16 micro-stepping allowing 3200 steps per-revolution from a typical 200 steps-per-revolution bipolar stepper motor.
For the joints that connect the vertically moving carriages to the plotting head I’ve chosen to use some reasonable priced ball joints from RS Electronics (a mere £2 a pop). They come dis-assembled which was a great opportunity to use my Dads treadle powered press for some production line fun.
And here are the assembled joints.
Note: This worked for my camera, It may or may not work for yours, do at your own risk. Also, apologies for the photo quality…my camera wasn’t working.
Just as I was about to take some photo’s to document a new blog post I turned on my camera and “Oh-Noes!! The lens has become fully extended and won’t go back in! and the camera is saying ‘Lens Error, Restart Camera’ Golly!”. According to various reports this is pretty much the death knell for the camera.
Now, I’m not in the habit of keeping receipts, and I think the shop I bought it from has gone out of business anyway. So I did the only sensible thing and decided to take a screwdriver to it.
Unfortunately I wasn’t expecting to actually fix the thing so I didn’t keep a record of the order of screw removal, but you basically have to keep unscrewing things until the side opposite the USB socket is visible as seen in the following picture.
You should now be able to see the large capacitor used for the camera flash, and next to it the side of an electric motor used for extending the lens when zooming. Just visible in the space between the top of the motor and a circuit board should be the two solder tabs at the top of the motor casing.
Next fire up a 5 volt power supply and attach some crocodile leads with small wires attached to the other side (I used the cut off legs from some resistors).
Next take the two leads and poke them on to the solder pads at the top of the motor. The lens zoom motor should start to turn. If your lucky the lens should start to retract, if not switch the wires around and try again.
When the lens is retracted back in reassemble the camera and try turning it on. If your lucky, everything should be working fine now!
If you’re like me you’ll probably end up with a few spares….I like to think of it as streamlining the camera…
Been meaning to post an update in a while, have a few new longer posts nearly written. In the meantime here’a a new project I’ve started after learning VHDL and FPGA related awesomeness.
Recently purchased a papilio Spartan 3E development board and I’m having a hell of a lot of fun relearning VHDL. To help apply some of the new stuff I’m learning I’ve decided to start a new FPGA project, the 8Bit Sequencer.
So far I’ve implemented 4 voices (sine, square, saw, triangle) with an octave, phase, and level control for each one, and also 2 modulator controls connected to an attack-decay-sustain-release (ADSR) generator, and a low frequency sine wave generator.
Below is a picture of the 8Bit output from the FPGA development board measured on an OpenBench logic analyzer. (The ADSR modulator is not connected, only the low frequency sine modulator)