I got the calipers off ebay (<10$) quite a while ago, but they kept draining the battery really fast. After i discovered this blogpost I decided to modify my calipers in a similar way.
The basic idea is the same:
replace the battery with a supercap
build a charging device
The only real difference compared to trevors project is the voltage used. I didnt have a 1.8V LDO around, so i decided to go with 3.3V.Â An additional SI-Diode in the charging-path drops 0.7Volt, so the actual voltage for a charged cap is 2.6V which seems to be fine for the caliper (i did no long-time test yet). Also, with that diode one cant blow the cap by charging with reverse polarity.
I only used parts you can get from the german distributor Reichelt. The cap is a “SPK 1.0F”, the switch is called ‘T215″.
I did not much testing yet. But the cap kept enough power to work with the caliper even after 80 hours ‘standby’ 🙂
Earlier this year my colleague RÃ¼diger and me build some LED-Letters and mounted them to the building front. The letters themselfes are made of 20mm Acrylic with buildin RGB-LEDs. A 3mm black Acrylic plate was added on top to cover the LEDs and generate more contrast for daylight conditions.
The control is build around the OLA Software. A Raspberry-Pi drives all the components. Two KarateLight devices provide 8 RGB channels each. A USB-Hub (which also poweres the Pi) and a USB-WLAN-Stick make the setup complete. The LEDs are powered by two 320Watt switching-mode PSU. Everyhting fits nicely into a steel cabinet which makes this thing waterproof. In order to organize the cables coming in at the bottom I build two combs which clamp the cables into place.
Since i dont have a cool DMX Application i wrote a few lines of python to generate a simple animation. Basically all it does is calculate a gauss-distribusion which is then shifted from left to right. Its quite simple and not well implemented, but it works: ola.python_fader.
I then use ola_recorder to store a single run of the script into a file. Playback is also done with ola_recorder running inside screen.
I bought my el-cheapo chinese lasercutter without a pilot laser. They did offer a visible laser for alingment, but that was just a simple laser-pointer mounted next to the main-laser-nozzle. It was kind of expensive (despite the fact that it was a really simple non-coaxial-design) so i decided to build my own.
From ebay i got two laser-modules in a cylindrical housing for about 21â‚¬ including shipping which already produce a line (they have a prism build in).
IÂ order to mount them i designed and build a bracket out of 12mm acrylic. Basically its a ring with a slot, i can slide it up the nozzle and fix its positin by tightening a screw. You can see how it looks mounted to the machine in the first picture.
Unfortunately i wasnt able to mount it further down on the nozzle. Now the laser angle is to steep and part of the laser is blocked by the nozzle itself (you can see the laser on the nozzle in the second picture). I managed to adjust it in a way that at least the pilot lasers cross in one point. Alignment in parallel to the working area required a little patience, but somehow i managed:
As a last job i wired everything up and slid the cables through the drag-chain. Since i was already soldering and installing additional wires, i also added two LED-Stripes to the portal to have better illumination while working.
Everyone who has been to a gaming convention/fair has probably seen chessex or q-workshop selling blank dice. I always wanted to use those blanks to create my own dice. Since I now own a lasercutter the time has come to finally manufacture some 😀
I used 16x16x16mm blanks which i got at this years RPC in Cologne. My lasercutter does not have any fixtures, rulers or clamping devices, so I needed to make my own. My simple fixture is a piece of 5mm HDF with a 16mm square cut out at an absoulte position. This allows me to align any futher engraving to those absolute coordinates.
After engraving the only thing left to do was to add some contrast. I used black acrylic paint to cover the engraving. Its quite hard to apply the paint only to the engraved areas, so I decided to rub the paint into the engraved area and remove excess paint after waiting a few minutes for it to dry.
I think it worked quite well 🙂
Now i am looking forward to create one custom dice for each player of my RPG group with a symbol matching their char.
Its an old Futaba FC18v3. I still had that one left from my first experiences with model aircrafts 15 years ago. I hate throwing stuff away, so I bought some new bits to make it usable again.
Now it features:
Powered with a 3C-Lipo (not shown in the pictures)
Blue Backlight LC-Display
FrSky DHT Transmitter module
Bluetooth interface for FrSky telemetry
The complete setup draws about 150mA @9V (with all modules powered on). That will make it run more than 10hours with a 1800mAh LiPo.
The Bluetooth and LCD module were both ordered from Ebay, the FrSky stuff from Hobbyking.
The installation of the different parts was pretty straightforward.Â I removed the old 40Mhz-PPM-Transmitter and soldered the 3 wires for the new 2.4Ghz module. The old antenna was removed, also i moved the CAMPAC module in order to use that space for the additional LED-and-pushbutton-PCB of the trasmitter module. The Bluetooth module only has 4 pins, GND,+5V,Rx,Tx which i all hooked up to the FrSky. Since the FrSky-Pins are RS232, i modded the module to output TTL-Signals by accessing the UART directly. Unfortunately i didn document that, but you can find several images on google how to do that.
Changing the LCD-Module also was quite easy. Its a standart HD44780 module with a 14Pin connector. Some of the pins are not used because the FC18 runs the display in 4bit-mode. Basically i just removed the old module and soldered the wires 1:1 to the new one. Then i added two wires for the backlight which also runs of 5V.
The last part was setting up data display on my smartphone. Fortunately some other people already took care of that. I just installed FrSky Dashboard. Done 🙂
I was in need of a cheap USB->DMX interface and decided to build my own. Searching the web I fould quite a lot DIY solutions. But most of them were unsuitable for me.
My design features:
low cost (about 10â‚¬)
open source: schematic and board are licensed CC-BY-NC-SA, the firmware is GPL (except microchip files)
a real rs485 transceiver
signal-generation by the Microcontroller (no bit-banging like the ftdi-dmx interfaces)
bootloader to update the firmware (thats what the switch is for – rescue mode)
fits into a ‘G027’ case (kemo-electronic)
If you take a look at the schematic you will see that the processor used is a 18F2550. But its possible and recommended to use the 18F24K50 which is cheaper and doesnt require a crystal oszillator. This is due to the fact that i made the initial design with the older controller (which i had at hand during the time).
On the software side there is a patch for ola. You will notice that reworked the ‘opendmx’ driver (i failed adding a new driver/directory to the build system).
There is no need to patch ola anymore. The karate-plugin is now in the mainline-tree.
Please respect the CC-BY-NC-SA licence when downloading and using it 🙂
Since i want to use telemetry with my soon-to-be-finished uavp-ng quadcopter i decided to use a FrSky two-way-telemetry system. Unfortunately the enigneers at FrSky choose to invert the serial signal which wont work on the hw0.24-mini.
Thats why i took a closer look at the receiver pcb. Fortunately it was quite easy to identify the UART-Pins with TTL levels. I removed the two transistors and some resistors which arent needed anymore.
The pinheader was also removed in this process. I added a bridge on ch3&4 to active CPPM-mode.
As a additional modificationÂ a voltage divider was installed. The AD2-Input of the receiver works up to 3.3Volt. With a 3k3 and a 10k resitor i was able to build a network with a convenient 1:4 scale factor. With 4*3.3Volt > 13V i can monitor the voltage of a 3S LiPo 🙂
This is how my Workspace looks after a few hours of debugging 🙂
I did some work on quadcopter-frames in the past, so inspired by the NG-UAVP-Project i decided to build my own quadcopter.
Since those guys offer blank PCBs i ordered some and build a Flight-Controller (hw0.24-mini-r2) and a Quad-Brushless-Controller (ngblc-r2). After some trouble with customs/taxes and missing parts i was finally able to assemble and test both boards. As always not everything works out of the box (soldering errors, missing parts, …).
Make sure to populate R68/R69. Those are current-limiting resistors for the backup battery for the Venus-GPS and the RTC. I left them open in the first place sind i didnt populate the battery. However, the Venus-GPS needs power at the Vbat-Pin to work. I spend about 3 hours searching for errors in the serial-communication :/
Check the supply voltages of each chip. The coil in the the LC-Filter for the MPU-Accellerometer was broken; however the MPU somehow still worked (eg got some supply current over clamping diodes), but did not answer SPI-requests correctly.
Cabeling is also an issue. The picoblade connectors are nice and small, but sometimes dont give good contact. I had some issues with the external-i2c-sensor bus because one pin didnt provide good contact.
There are still some open issues:
The LIS3L-Accelerometer wont get recognized on the SPI-Bus
On the ngblc there seems to be at least on misplaced part. On of the supply-voltages drops down because of overcurrent. I am still investigating this.
As next steps i will finish the mechanical setup. Mount the motors to the frame and do some wiring.
Its made of 5mm HDF wood.Â I did a google-image-search to find suitable pictures and traced them in Vcarve.
The text and the DIN-Label-Box in the lower right were exported from eagle. I was to lazy to draw them myself.
In the first version i just cut along the vectors which resulted in a really tight fit. The gear was almost impossible to remove and put in again. For the second version i duplicated the lines with an offset of 0.3mm which did result in a larger gap. Now all the parts fall out by themselfes if you turn the puzzle around.
The two sheets were glued together with basic wood-glue. The lower sheet also features ‘eject-holes’ (you can see them under the ruler and nut). That way you can push out the pieces from behind.