The end of our project is approaching so we have started to think and work seriously in terms of how our final robot will look like, since so far we have made prototypes and different proofs. So,at the beginning of October we started with a meeting where we are consult mostly for our final design.
- Check the material list we’ll order with Yll
- 3D prepare the concept of footpads and legs with Albulena
- 3D design the legs and present a technical Inventor drawing (dimensions included x, y and z)
- Help Era on preparing the documents for our final paper work documentation
- Work with Nathan for the silicone we’ll be testing with this week!
- Help Drilon with the orders
- Finish a video which will be representative of RCWT ( the idea, editing and text) you will share your ides on 9th of October 2018.
- Collect all the data from what we’ve wrote down during the last months, and start creating new documentation papers for each experiment we’ve finished until today.
- 3D design the molds for silicone.
Albulena’s task for the first week of October, was to 3D design a leg. She 3D designed the leg and also prepared a technical specification. First the leg has three parts, the first two parts connected to the servo and the third part connects the first to the second. This leg is thought to work with two servo motors. To the wider part of the leg (the beginning of the foot) it is thought to be placed silicone which means it is footpad.
We’ve started entering the final and the most interesting phase of our project. The next few months are crucial for us and the project. Because this phase is more advanced and detailed, we saw the need for money to buy new components. For the next and final robot we’ve changed the entire electronic system.
All electric components are listed below:
Digital Hitec Mini Servo– These are Digital Hitec Mini Servos. There will be 12 servos of this kind that will be responsible for the movement of the robot. They’ll be separated into 4 groups of 3 servos(1 group per leg). The weight of 1 servo is 14.2g, so 12 servos equals 170.4g(1 DC motor in previous robots weighted 250g). Their operating voltage range is 6-7.4V and stall current draw is 1.3A(at 7.4v during heavy workload). Torque range is 3.0 kg-cm / 3.7 kg-cm wich is plenty for our robot and it’s weight. The best thing about these servos is that they’re digital and a lot of their features can be programmed for a specific use.
Digital Hitec Micro Servo- These are Digital Hitec Micro Servos. There will be 4 of these servos, and their main job is to peal the fingers but the need for finger pealing is still being debated because maybe we will use only pads. The weight per 1 servo is less, around 9g,. Torque is 1.2 kg-cm / 1.5 kg-cm and operating voltage is 4.7 – 6V.
PC Programmer– The only reason that we bought digital and not analog servos is their programmable features, and the programming of servos is made through this device. This is a special device made for Hitec Servos. It allows us to connect the servos to PC and through the program change their specifications.
Arduino MotorSheild rev3- In previous robots we used Arduino MotorShield rev3. It was a great board that could be attached in top of arduino and allowed us to controll the Dc motors, it also had specialized pins but unfortunately it wasn’t strong and didn’t have pins enough to controll 12 servos. After making some research we found Adafruit 16-Channel 12-bit PWM/Servo Driver – I2C interface. This board allows us to controll up to 992 servos because you can connect 62 of these board in a chain. But we only need 1 board for our project. You could ask why use a specialized controller when you could just connect 12 servos to arduino? The main reason is the delay and over-loading of the main processor. This board has a specialized chip that removes these problems. Also it has a built-in current protection circuit and it has a specialized library for servo controlling.
Pololu Adjustable 4-12V Step-Up Voltage Regulator- This is a Pololu Adjustable 4-12V Step-Up Voltage Regulator. What this board does is that it can take an input as low as 2.9V and output a steady 4-12V.Why do we need to use this board? Our robot’s power comes from a battery pack, and during work batteries don’t output steady current and voltage. These drops can damage our board even though it has built-in circuit for preventing damage but during heavy workload of servos the current draw can be up to 6A or higher, and to eliminate every possibility of damage we will use this board. It also has a potentiometer so you can change the output voltage to your desire.
Lithium Polymer Batheries– This battery pack will juice up our entire robot. Lithium Polymer batteries are a great choice for robot batteries because they have great capacity-to-weight ratios, giving you lots of power for very little weight.Our Lion 7.4V 4500 MAH 30C Battery is a great medium sized battery that can discharge up to 55A continously! To make it easy to connect/disconnect the battery from your project, each of these batteries has a Female T-Connector. In previous robots to charge the batteries we had to unweld every battery and charge them one by one with a power supply, but this battery you can charge with a special charger made only for this purpose.
Max B6 Digital RC Lipo NiMh Battery Balance Charger– This the charger that we will use to charge our powerpack. This charger has a Charging Current Range: 0.1 ~ 6.0A and our battery only needs a steady 2.2A to charge up. It also has a over-charge battery circuit so it will stop when the batteries are fully charged.