3D Printing and Robotics: My Stories

1/30/2017

Introduction/Motivation:

I've always wanted a RC car. The last RC car that I have when I was a child was one of those old crappy wired one because I couldn't afford the wireless one. Now that I've obtained enough engineering skills in the field of electrical/mechanical and software I've decided to just build my own.
The idea is to use 2 microcontrollers that talk to each others via the RF. That sounds simple enough.

I bought a pair of 422Mhz Transmitter and Receiver and they worked great. YAY!. The price was very cheap too. A pair for a staggering 70c from eBay and hey! what could go wrong right? Next thing I know, well it's kind of my fault I shorted the receiver due to my stupidity when I left the solder wire in the open when I was testing out my motor driver. So when the receiver got fried I bought another pair on eBay and now the range is literally limited by 1m. So I'm going to remodel my entire design for optimization and performance. Here's the list of parts that I was getting. You can easily find these on eBay or Amazon. If you are first using amazon don't forget to contact me for that sweet sweet first timer deal hehe.

Transmitter parts:
1 Arduino nano
1 9v battery
2 Joystick breakout boards
1 OLED display module
1 switch
1 NRF24L01 Transciever module sitting on top of its 5V adapter.

Receiver Parts:

1 Arduino nano
1 9.7V LiPo Battery
1 High Torque Servo
1 High Torque Brushed DC Motor
1 L98N Motor Driver
multiple resistors
1 5V regulator
1 Buck converter
1 NRF24L01 Transceiver module

2/3/2017

Choosing The RF Devices

To begin with. I started with the 433 Mhz pair of transmitter and receiver. You can find these on eBay for as cheap as 70 cents a pair.

The first pair that came to me worked great, well it took more then 20+ days to arrive but I was in no rush. I was never in a rush actually that's why my project keeps dragging and dragging. Anyway. They worked great. They got some OK range. About 10m in my experience, however though. These guys have a ton of noise and there is little error correction. Result of that? some time my servo would freeze for a good 2s before I move closer to range. I was a little bit bumped but it was still a prototype anyway.

Then I fried it on accident (which I'm kind of glad I did) when I was testing out my PCB design. I acidentally place my PCB righ on top of the solder wire which happens to be on the way of the 12V and the GND pin. I burned the wire and fried my Arduino nano along with the receiver that was on the board. So the lesson here is please don't make the same mistake that I did and always put your solder away when you are done.

After I fried it I bought a new pair (waste of my money) and the new pair doesn't work as well as the last pair. It was giving me some horrible range of 2 meters max. I literally wanted to smack myself in the face. Anyway I was looking at a new devices and here's what I found.

1. NRF24L01 WiFI 2.4Ghz transceiver

This is an amazing pair and I would suggest it to everybody. Furthermore if you want to upgrade your range you can use the antena adapter that are out there and it boots your rage up to freaking 800m (on paper). Which is pretty crazy. I might be using it for my drone.As for right now. This is good enough. I'll probably be talking about how to use these in future post as well as sharing the code. There are two Arduino libraries out there for these. One from RadioHead which works fine. RadioHead is just like a daddy of Arduino RF, they have libraries for pretty much all RF devices that I know of. Anyways they work, but not as well as this awsome library; it is call the NF24 library from the author TMRh20. I would recommend this library to anyone. The trick is that there is a 3 essential functions that maximize your range. I was getting around 4m with RadioHead and more than 50m with this library. So the 3 functions are set_range(250), set_PA_level to maximum and payload bits (the less bit the less payload weight). I'll go into details in the next post. Oh and I forgot to mention, it is 2.4 Ghz. Amazeball.

2. HC-05

Next stop we have the HC-05 or HC-06 BLE module which runs ble 2.0. This is ideal if you like to develop your project on mobile devices. I bought these for my next project, which is the drone. But I realize that since I'm using an Apple device. I'm going to need ble 4.0 which leads me to the next module.

3. HM-10
We have the HM-10 blue module which is compatible with ble 4.0. Which means we can run it on my iPhone. Cool, I'll get into that on the next project. Right now I just want to finish up with this RC vehicle project.

I'm a little bit happy and sad at the same time looking at these. They are not completely perfect but they're taking shape. Slowly anyway. The printer that I'm using is the MP select Mini, which is a fantastic printer for just under $200. It's my new game console, I love it.

I'm re-designing my controller and I'm adding a LCD screen to report battery life and maybe position of the Receiver and maybe other things.

2/4/2017

Current challenges:

1. I still need to work on the output joint shaft it does not fit very well with the differential output.
2. Print out a spacer between the chassis and the rear tower so that they match.
3. Design the front shock mechanism.
On the right is my Chassis, which consists of a motor holder that is printer out using wood filament. It came out so nicely. And below it is gate that connects to the rear tower, problem is the rear tower is printer with 20% infill so it is very weak. when I tight it in the surfaces literally gets compressed. I might have to redesign it.

That's my Servo holder. It came out okay. I boost the infill on these parts to 70% so they are quite strong. Although they are still PLA. ABS would be ideal but I don't think I will be printing ABS soon. I have 4 rolls of PLA filament left. ( I know I got carried away, they're just so nice).

Everything you see here is designed by me. Please feel free to contact me if you want to the STL files.

-Kyle-

2/8/2017

The Re-designing

I'm performing major upgrades for my RC including better front axle and steering system. The old steering system does not work very well. The old axle are also not performing as well as I thought. Mainly because the two wings are separated. So when the car weights down in the middle, the shocks alone can not handle that much weight. Now I'm printing a connected front axle system.

The controller is also getting an upgrade, now added a cool oled display. Right now for testing purposes just the status of the transmission. I plan to add more later.

2/14/2017

February Updates

I'm redesigning the pretty much 90% of the robot to improve performance and durability. I started with the front axle and steering system. The old axle system does not function well due to the fact that the shocks are not aligned properly. And the left and right axle are not connected in one piece. The separation causes the system to be unstable under the weight.