30 juin 2015

3D Printer

Ok, I finally decided to buy a 3D printer :)

My choice went to a Delta printer, which look more simple and efficient than classical Cartesian printer. This one is named "Kossel".
I decided to go for the Kossel XL which is big enough for the parts I will need to do. This printer is  sold by the excellent shop www.builda3dprinter.eu.  This type of printer is  very quick and accurate compared to Cartesian.

The assembly of the various parts was quick, and if you follow carefully the build manual step per step, there should be no problem.

One thing however, my kit miss one part to adapt the new heater head E3D. This heater replaces the old version which is apparently less efficient. But as I could not wait to receive that part :-D, I cut one with  my CNC. This is the black plate on the picture below.

Electronic assembly: I used the part delivered in the kit which consist of : Arduino mega 2560, Ramp 1.4 + Steppers, LCD display with button.
First thing is to install  jumpers and steppers on the Ramp 1.4. For best resolution, I put jumpers everywhere below the steppers A,B,C,D.  I am not sure the one for D is needed, but anyway:
On A, the jumper are hidden by the stepper already pluged in.

Next, I plugged one motor as  I wanted to test that first motor was working. But this was a bad idea, read more to understand why.
First thing  is to load the firmware into the mega2560. I used "Marlin" firmware. This is "classic" arduino stuff , no surprise.
Before loading the firmware, you  should have configured the firmware with "configuration.h" file.

The first thing to configure in "configure.h" is the LCD display. This is what I did. But problem, impossible to see anything on the LCD after powering on... Only blue  screen on the LCD.  After searching for a couple of hours,  triple checking  the configuration.h, the wiring, etc.... I finally  tried to rotate the small pot which tune the constrast  on the LCD ! And Oh miracle, that was it, now LCD display information. Stupid guy ;)

So then I wanted to make a move of the first motor.   This was an error to think that such a simple test  could be done so easily.  I was  wrong because the firmware has integrated  hardware protections which prevent you to start motor if some conditions are not met. In this case, it was the home switch which was not installed..

And this is where come the fun :-(, when connecting the home switch to the RAMP 1.4, you have to be very careful otherwise you may burn your Arduino... This is what happened to me.

The Ramps 1.4 has 3-pins instead of 2 pins connector for the switch, and if you don't pay attention, you will conect + and - instead of  S and - !

So I did burn the Arduino mega 2560, but fortunately I had an old mega1280 in stock. Fortunately, Marlin software fit in that board also.

So I coud continue the tests.
Now, I thought that I was ready to test one motor (the one with stepper on). So I enter the menus on the LCD  and enter the menu for movement on X, Y and Z.

And then, nothing happen.   Only the return home menu was doing something on the motor, always in the same direction.

It took me some time to understand that returing to home is REQUIRED before anything can be done on motors. And to have the returning to home working, your motor and the home switch need to be properly installed...

To be continued....

21 octobre 2010

Converter I2C to PPM

This is a protocol converter for I2C to PPM. It allows the use of standard ESC controler on Mikrokopter or similar.

One of the major drawback of I2C currently, is in case of severe failure on one controller, you may impact all other controllers connected to the I2C bus and lost all motors.
Choosing PPM is more reliable, as each controller is connected separately, it may not interfere with others and reduce a lot the risk of loosing all motors. It allow also to use well proven standard controller with a wide range of choices.

- I2C input from Mikrokopter or similar Flight Control supporting same I2C protocol
- output PPM signal suitable to standards ESC motor controllers
- support 4 or 6 controller (8 controller version coming soon)
- optimized for Turnigy plush or TowerPro Mag8 (re-flashed for Fast PPM)
- smoother motor handling
- PPM frequencies available: 400 Hz (recommended), 200 Hz, 50 Hz (for standard servos)

Any ESC may not work good enough for smooth control on a multikopter. If unsure, tests to check both PPM frequency and motor reactivity.
Also, there is *no* feedback from the ESC to return current or temperature from the controllers, so information such as current consumption from the controllers will not be available anymore.

The version 4/6 from Flyboard is available here:

09 octobre 2010

Update on DSSS and video TX

This is an update to my previous measurements and comments on DSSS/FHSSS technology:
Some spektrum measurements

Recently I had problems with transmission video. It looks that some videos TX in 900 Mhz or 1.2-1.3Ghz band may generate harmonics on the 2.4Ghz band. See this thread:

So it may be very dangerous if you switch ON your RC equipment *before* the video TX: as in DSSS only 2 channels are used, you may well be unlucky and your RC may choose some channels that will be used also by the harmonics of your video TX.

To reduce this problem, you may try to switch ON your RC *after* switching ON the video TX, because then the RC will choose a free channel among those remaining free by the video TX.
But this solution is not very safe, there is another one here:
low pass video filter or here.

Overall, surely the best solution is to add this filter, but you can note that DSSS technology is not very safe in that situation.
Unless DSSS system could dynamically reallocate a new channel if the current one is detected as being saturated, FHSSS or better AFHSS has more chances to work fine in this environment, as shown here:
Review: Hitec Spectra AFHSS 2.4GHz receiver and Optima 7 module (part 2)

11 juin 2010

PPM serializer v2

A new version of the serializer is ready.
It features:
* channels from receiver are serialize on one wire
* Compatible with Mikrokopter electronic and more RC receivers
* Neutre stable on all channels
* available in 8 or 12 channels (PPM8 ou PPM12)
* with external crystal for better temperature stability
* all channel entries are protected

You can buy it at the shop www.flash-rc.com in Mikrokopter section.

12 avril 2010

Some news about the project

It has been a while since I have updated the blog. In fact, I was waiting for a supplier to cut the aluminium plate for the transmitter. But unluckily, the supplier could'nt do the job after 3 months. This is a bad news :(. So I now have to find another solution, or do it myself (a good method also).

Meanwhile, I have been working on a PPM serializer for Mikrokopters. It is now finished and available in the shop "flash-rc". The PPM serializer allows to put 8 channel on one single wire for the Mikrokopter Flight Control.
This board can also be used for other purpose in electronics. It has:
- Port D and Port C protection with resistors
- Quartz 16 mhz
- voltage regulator (5v or 3.3v in option).

If you interested to know more about it, please contact me.

A picture of the prototype:

24 janvier 2010

Bending aluminium

To bend aluminium for the enclosure, I built a simple basic machine make with plywood and some metallic rigidifiers. With the tube installed, the round corner is 10mm radius, which is exactly what is need for the transmitter enclosure. The thickness of the alu should be less or equal than 1mm. Some pictures below:

Bending aluminum 2

The second corner: