08/19/2014 at 03:38 •
In order to drive the motor I don't need to use another microntrollers board because the Raspberry Pi capable to run Motor driver motor directly.
For the motor driver I choose the L298n motor driver module because it can give 2 A to the motors and has 4 mounting hole that can be attached with nut or spacer and also it is quite cheap ($3 at amazon)
The specs told me that it need 5v logical input and raspberry pi have 3,3v output from the GPIO. But on the first try it can take the 3,3 V input from the raspberry pi. and it also run well. the robot move smoothly no matter what kind of chassis it used.
it also have onboard heatsink that can make L298 IC little bit "cooler"
08/19/2014 at 03:14 •
For the first robot prototype I use any material that was laying around my workstation. I found my cheap RC car that was used for my previous arduino project. So I unplugged the Arduino and plug in the Raspberry Pi to the RC car chassis
this first prototype run very well and fast. Next I need to make it more good looking
The 2nd prototype I used a track set kit from tamiya, after arranging all the parts and cables i got a better result
but I still not satisfy with this chassis and it runs unstable because the weight problem.
For the 3rd and final prototype I Use the RP5 Tank and it look better than before
not only all the parts attached neatly, the robot runs very stable with this chassis.
08/19/2014 at 02:57 •
After successfully make this robot run on a local network, the next step is to connect this robot to the world (via internet). After a few google hunt, they say I need to do a port forward and ip public is needed. If i dont have ip public I can use dynamic DNS service, but most of them does not come for free. Because It need a little bit hectic configuration and I also don't have any international money account (difficult country regulation), I need find the another option.
Then I found pagekite from http://pagekite.net/, it is a service that based on python. I just download a few files and sign up free. After that just launch the pagekite app and the robot now can be access online anywhere. But there is still problem with this, because it only have one month trial and to continue the service I have to pay, the service is really cheap actually but I dont have any account to make the payment.
After another google hunt I found about tunneling, and there are a lot of tunneling service. Then I choose ngrok from https://ngrok.com/ because of its simplycity. After signing up and get a token key, I insert the token to the raspberry pi and then launch the ngrok application. because I have already sign up I can choose any subdomain I want as long as it is not been used by other user. And the very great thing about this service is, it is free forever and does not require any difficult configuration.
08/19/2014 at 02:31 •
This robot use two power source, one for the Raspberry Pi and one for the L298n Motor Driver.
For the raspberry Pi, I use two kind of USB battery Pack.
1. One with the big size has the capacity for 10.000 mAh with two output for 1 A and 2 A. with this battery Pack I can turn on the raspberry pi for 8-9 hour straight. but the problem here is the size for the battery pack is too big. On my not so big chassis, I need to forcely fit the battery pack, and the result was not good
2. The second one is a smaller one with the capacity 5600 mAh and has one output for 1 A. Surprisingly the whole size of this USB battery pack fits perfectly to my chassis. It has shorter time to turn on the raspberry pi (4 hour) but I think its enough.
For the L298n Motor Driver I use AA baterry with the minimum voltage of 6 V:
1. First I use a pack of 4 AA alkaline battery that give 6 V to the motor driver module. Using this pack the wheel of the robot runs perfectly stable because the motor driver give 2 A current which is sufficient to make the robot walk normally. But again the size for this battery is too big for the chassis, and after 1 hour controlling the robot, the battery run out of power and I have to change the battery again and again.
2. Later I use AA 3,7 V UltraFire Rechargable Battery. For this battery I only use two pieces and it already give me 7,4 V for the motor driver module. Since the module can receive voltage up to 12 V, I don't need to add a power regulator. Because it only use 2 pieces battery, I can fit this battery pack anywhere I want in the chassis. It can make the robot run longer than the previous one for about 2 hour run time. And everytime it run out of power I just need to recharge it again