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46  Using Arduino / Networking, Protocols, and Devices / Re: Two nRF24L01+/Arduino UNOs don't talk to each other on: July 05, 2013, 06:10:28 am
I have used the nRF24L01 modules in several projects. Try this: http://www.bajdi.com/sending-structs-with-nrf24l01-modules-and-the-rf24-library/
47  Topics / Robotics / Re: Inverse Kinematics for Hexapod on: June 25, 2013, 02:56:38 pm
Programming a basic walking gait using servo.write(angle) and then a delay is very easy.
Then you get something like this: https://vimeo.com/61460555

I'm not much of a programmer, the challenge for me was to program it using inverse kinematics and using a timer. That's a lot harder for someone that is new to programming.
A couple of months later I ended up with this:
https://vimeo.com/67994924 
I can now remote control (by using another Arduino as a remote and 2 nRF24L01 modules) it, and make it walk in every direction. With the remote I can let it do preprogrammed "moves". Also has an autonomous obstacle avoiding mode using ultrasonic sensors and with the WiiCamera sensor it can track IR light. I also added 18 leds, 16 of them controlled by 2 shift registers. Mixing all those things in one sketch took me a lot of time to get right. My last sketch is over 1500 lines of code. But I'm sure someone with better programming skills could do it a lot simpler. 
48  Topics / Robotics / Re: Inverse Kinematics for Hexapod on: June 25, 2013, 02:30:25 pm
I recently built a hexapod, well it took me many months to program it smiley I used inverse kinematics, I found the following site helpful -> http://www.engineer-this.com/IK.shtml The IK wasn't that hard to figure out. The biggest problem for me was coding the whole walking gait based on a timer (millis). I didn't want to use the delay function as I wanted to let the micro controller do lots of other things.
You can read about my hexapod on my blog: http://www.bajdi.com/category/bajdupod-996r/
49  Community / Exhibition / Gallery / Re: My Arduino hexapod monster: Bajdupod 996R on: June 17, 2013, 07:28:04 am
Yes the Lynxmotion servo controller is good solution. I actually have a Chinese (Torobot) 32 channel servo controller. I plan on rewriting my code one day using it. It should be much easier to make the servos move smoothly with those controllers.   
50  Using Arduino / General Electronics / Re: RTC timer help on: June 15, 2013, 05:52:41 pm
If you google Arduino + DS1307 you get over 100000 results.
51  Using Arduino / General Electronics / Re: RTC timer help on: June 15, 2013, 05:08:39 pm
I once wrote a sketch to blink a led using a DS1307 rtc. You can find it here: http://www.bajdi.com/blink-without-delay-and-millis-but-with-a-ds1307/ Don't just copy/paste it. Please try and figure out how it works.
52  Community / Exhibition / Gallery / Re: My Arduino hexapod monster: Bajdupod 996R on: June 13, 2013, 11:07:54 am
The only code I had was the math for the inverse kinematics. Which actually is not that hard, there are lots of websites that explain how it works.
My biggest problem was coding the walking gait. I first wrote a sketch using a for loop and the delay function to move the servos. That was pretty easy. But when you want the micro controller to do a bunch of other things you're in trouble. So I tried dozens of ways to code the gait using the millis timer, after a dozen revisions of my code I finally got it right.
I did look at the Lynxmotion code before I built my hexapod, but it's pretty complex. I can't understand much of it.
I name it a monster because it uses so much current. I once tried to power it without the UBECs, and connected the servos directly to my lab power supply. I saw the current shoot up to almost 20A. I'm using very cheap metal geared servos (standard size), Towardpro MG996r servos. They cost less then 5€ a piece and have +10kg/cm torque.    
53  Community / Exhibition / Gallery / Re: My Arduino hexapod monster: Bajdupod 996R on: June 12, 2013, 11:31:19 am
No hexapod lovers on this forum?
54  Community / Exhibition / Gallery / My Arduino hexapod monster: Bajdupod 996R on: June 09, 2013, 02:54:20 pm


My hexapod has an autonomous mode and a remote controlled mode. In the autonomous mode it can track an IR light source using the WiiCamera sensor and avoid obstacles which it detects with 2 ultrasonic sensors. In the remote controlled mode I can let it walk in every direction. I also have a mode to move the body without moving the tips of the legs, this is where inverse kinematic comes in very handy. I also programmed a “fitness mode” where the hexapod lift 3 legs of the ground and moves them up. In the last mode I can control each leg individually, you can see this in the last part of the video. My code is far from perfect, but it works smiley
It was not easy to program all these things and let it all work together.

This is a list of parts that I have used in my hexapod:

Mechanical:

    Hexapod chassis kit (bought on Ebay)
    3x laser cut acrylic plates (made by local shop)
    6x bearings (to mount the underside of the servo brackets)
    Acrylic ultrasonic sensor bracket (bought from Rocket brand studios)
    Pan/tilt kit (for WiiCamera sensor, bought from Rocket brand studios)
    18 metal servo horns
    Lots of M3 nuts and bolts

Servos:

    18x MG996R servos (bought on Ebay)
    3x SG90 servo (to move the sensors, bought on Ebay)

Electronics:

    3x 8A UBECs (bought from Hobbyking)
    3S 3000mAh Lipo battery (powers the 18 MG996R servos)
    2S 1000mAh Lipo battery (powers the 3 SG90 servo and sensors)
    20A automotive blade fuse (protects 3S Lipo battery, bought on Ebay)
    In line fuse holder + 1A fuse (protects 2S Lipo battery)
    Servo power distribution PCB (own design, made by Seeedstudio)
    Seeeduino Mega2560
    ATmega328 board (own design, made by Seeedstudio)
    nRF24L01 module (wireless control, bought on Ebay)
    2x HC-SR04 ultrasonic sensors
    WiiCamera sensor (bought from Rocket brand studios)
    2 x 74HC595 shift registers (to control the 16 leds)
    18 blue leds
    18 220 Ohm resistors
    4 resistors for 2 voltage dividers (analog reading of the 2 Lipo batteries)
    Perfboard, lots of wires
    LM2596 PCB (powers the 3 small servos, leds and sensors, bought on Ebay)

I reused the remote control (based on an Uno, joystick shield and nRF24L01 module) from previous projects. This project cost me quite a bit of money. During the building of Bajdupod 996R one servo burned up. Yes only one, I can assure you these servos have had a very hard time. So I am quite surprised that I did not burn up more servos.

Quite a bit of time and money was spent on powering this hungry beast. I initially used 2 8A UBECs and killed them pretty fast. Then I bought 3 more 8A UBECs and designed a new power servo PCB. Then I destroyed a 3S 3000mAh Lipo battery. I had to recharge the battery so many times that the Lipo charger died on me. Luckily I had 2. The hexapod eats Lipo’s for breakfast, lunch and dinner. The battery lasts less then 10 minutes.

Coding this beast has taken up most of my free time the last couple of months. I would have never thought I would be able to program such a complex project one year ago. I have only been playing with Arduino for one year and a halve, before that I had never written a line of code. I’ve never taken any programming courses, everything I’ve learned comes mainly from lots of trying and testing. I can assure you it took me lots of dedication and hard work to accomplish what you see in the above video smiley

55  Using Arduino / Motors, Mechanics, and Power / Re: 28BYJ-48 5-Volt Stepper on: June 08, 2013, 05:42:32 pm
I wrote some non blocking code (not using the delay function) for these stepper motors a little while ago: http://www.bajdi.com/non-blocking-code-for-the-28byj-48-stepper-motor/

I have just written some code that controls 4 of these little stepper motors using 2 74HC595 shift registers. So I'm controlling the 4 motors with only 3 pins. Will post it later on my blog.
56  Using Arduino / Motors, Mechanics, and Power / Re: SG90 Servo Difficulties on: June 04, 2013, 02:22:15 pm
Well I'm afraid you have a broken servo... There is probably something wrong with the pot or the wiring from the pot to the little controller board in the servo.
57  Using Arduino / Motors, Mechanics, and Power / Re: Problems with 2 servos on: June 02, 2013, 03:20:30 am
You also have a led connected to the Arduino but aren't using a resistor to limit the current. That's basically a short cut.
58  International / Nederlands / Re: Goeie winkels voor electronica (online en offline) on: May 25, 2013, 08:11:05 am
Ik ben ook een grote fan van Ebay. Koop ook regelmatig electronica componenten bij Tayda Electronics, zitten in Thailand maar versturen vanuit Singapore. Laatste bestelling arriveerde na 10 dagen. 
59  International / Nederlands / Re: Elektromotortje aansturen zonder motorshield on: May 25, 2013, 08:08:25 am
De Arduino 5V regulator (ncp1117st50t3g) kan maar 1A max leveren. Ik zou het nooit zover laten komen. En daar moet alles van de arduino van gevoed worden. Dus ik zou ook een aparte voeding maken voor motoren ed.

Die 1A in de datasheet moet je wel juist interpreteren. Die ncp1117 is een lineaire spanningsregelaar. Als de voedingsspanning bijvoorbeeld 9V is en die regelaar moet 1A stroom geven dan zal die regelaar 4W (4*1)aan warmte produceren. Die ncp1117 op de Arduino is een kleine SOT223 package, die kan nooit zoveel warmte dissiperen. Afhankelijk van de voedingsspanning ga je best niet boven de 200-300mA anders zal die regelaar snel zeer warm worden.

60  Community / Bar Sport / Re: Your latest purchase on: May 23, 2013, 11:24:38 am
I also have 2 of those VS1003 modules. I've found several Arduino libraries and code for that module but I can not get it to play an mp3 from an SD card. I can get it to work in midi mode though with the library from Maniacbug. (Maybe we should start a new topic about the module.)
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