Monday, November 20, 2017

Comparison of three maker boards. ESP32, Pi Zero W, C.H.I.P





Both the pi zero w and the C.H.I.P support linux. I like the fact that the C.H.I.P comes with on board battery management and audio. The C.H.I.P does not have on board HDMI by default and is a little bulkier than the pi zero w. The pi zero w has built in HDMI and micro SD. The ESP32 board does not run full blown linux but is compatible with the Arduino IDE. The ESP32 supports WIFI and some bluetooth functionality (the espressif SDK does not support pairing yet).




ESP32 dev board cost: $12
Raspberry Pi Zero W: $10
C.H.I.P.: $9


ESP32 Specifications:
    Processors:
        CPU: Xtensa dual-core (or single-core) 32-bit LX6 microprocessor, operating at 160 or 240 MHz and performing at up to 600 DMIPS
        Ultra low power (ULP) co-processor
    Memory: 520 KiB SRAM
    Wireless connectivity:
        Wi-Fi: 802.11 b/g/n/e/i
        Bluetooth: v4.2 BR/EDR and BLE
    Peripheral interfaces:
        12-bit SAR ADC up to 18 channels
        2 × 8-bit DACs
        10 × touch sensors (capacitive sensing GPIOs)
        Temperature sensor
        4 × SPI
        2 × I²S interfaces
        2 × I²C interfaces
        3 × UART
        SD/SDIO/CE-ATA/MMC/eMMC host controller
        SDIO/SPI slave controller
        Ethernet MAC interface with dedicated DMA and IEEE 1588 Precision Time Protocol support
        CAN bus 2.0
        Infrared remote controller (TX/RX, up to 8 channels)
        Motor PWM
        LED PWM (up to 16 channels)
        Hall effect sensor
        Ultra low power analog pre-amplifier
    Security:
        IEEE 802.11 standard security features all supported, including WFA, WPA/WPA2 and WAPI
        Secure boot
        Flash encryption
        1024-bit OTP, up to 768-bit for customers
        Cryptographic hardware acceleration: AES, SHA-2, RSA, elliptic curve cryptography (ECC), random number generator (RNG)
    Power management:
        Internal low-dropout regulator
        Individual power domain for RTC
        5uA deep sleep current
        Wake up from GPIO interrupt, timer, ADC measurements, capacitive touch sensor interrupt

Raspberry Pi Zero W Specifications:
The Raspberry Pi Zero W extends the Pi Zero family. Launched at the end of February 2017, the Pi Zero W has all the functionality of the original Pi Zero, but comes with with added connectivity, consisting of:

    802.11 b/g/n wireless LAN
    Bluetooth 4.1
    Bluetooth Low Energy (BLE)

Like the Pi Zero, it also has:

    1GHz, single-core CPU
    512MB RAM
    Mini HDMI and USB On-The-Go ports
    Micro USB power
    HAT-compatible 40-pin header
    Composite video and reset headers
    CSI camera connector

C.H.I.P Specifications
Now-discontinued CHIP is the original board, mostly targeting hobbyists. The system is built around the SoC processor R8 from AllWinner as its core, which integrates an ARM CortexTM-A8 CPU (based on ARM architecture V7-A) and peripherals, such as Graphic Engine, UART, SPI, USB port, CIR, CMOS Sensor Interface and LCD controller.[13] The CPU is also accompanied with NEON SIMD coprocessor and has RCT JAVA-Accelerations to optimize just-in-time (JIT) and dynamic adaptive compilation (DAC).

Features implemented on this model:

    Built-in Wi-Fi B/G/N, Bluetooth 4.0
    Full USB port and USB On-The-Go port
    Composite video and stereo audio port via mini TRRS
    Optional composite TRRS to RCA audio-video cable
    Optional VGA adapter and HDMI adapter (see Hardware extensions below)
    Open source hardware[14] and open source software
    Up to 45 GPIO ports
    Supports 1-Wire and I2C protocols, PWM output
    Serial console and Ethernet via USB for quick headless operation
    Can be powered by battery
    Onboard storage, pre-installed Linux OS (Debian)
    Web-based firmware update

The CHIP is 60 mm × 40 mm in size.

Sunday, October 22, 2017

Amateur manned multicopters. Flying cars are just around the corner.




Flying cars are just around the corner. Over the past several years there have been many examples of manned multicopter vehicles. Anyone that has several thousand dollars to spend on hobby aircraft parts and lots of free time can build a manned multicopter. Its not as complicated as one would expect. Someone can take hobby aircraft parts including electronic flight controllers and use them without much modification. Most of the manned multicopters use hobby parts meant for large scale model aircraft. Large high output brushless motors paired with large hobby propellers.




The biggest challenge with a manned multicopter is not lift, hobby motors and propellers are able to provide enough lift. Packing enough energy density into a power system to get a long flight is one of the biggest challenges. Building a manned multicopter becomes a balancing act, weight vs. lift vs. energy.
Increasing lift adds weight and uses more energy. Increasing energy adds weight and requires more lift. Increasing weight requires more lift. The props need enough power collectively to lift the vehicle and the passenger and power supply.




The power supply used for these type of experimental manned multicopters are usually an array of lithium based batteries. At the moment lithium based batteries provide the best energy density needed for a manned multicopter. The batteries are heavy and this means there is a limit to the amount of energy that can be carried onboard. Most of the experimental manned multicopters are only able to fly for 15-20 minutes max.

Some people have claimed that multicopters do not scale. One reason they cite is that larger props have too much momentum to be able to make the small changes in RPM needed for stable flight. Even the larger props are so light that this is not as much of a factor as some people think. There are a couple solutions to this anyway. One solution is to use many smaller propellers to gain enough cumulative lift. Other solutions people are working on are things like variable pitch props that change the amount of thrust instead of altering the RPMs of the rotor.



Battery technology is the limiting factor in this case. If there is a substantial breakthrough in consumer battery technology, then almost anyone could have a flying car. And they would not really cost too much looking at a minimalist build. Really light and strong modern materials like carbon fiber and ETFE can be used to further reduce the weight. For safety purposes someone could install a ballistic parachute commonly used on ultralight aircraft.

References:

https://en.wikipedia.org/wiki/ETFE
https://en.wikipedia.org/wiki/Carbon_fiber_reinforced_polymer
https://en.wikipedia.org/wiki/Ballistic_parachute










Monday, October 16, 2017

Is an amateur cube-sat launch possible?

Would it be possible for a volunteer based crowd-sourced project to launch a satellite into orbit? I think it is possible. Cube sats are micro sized satellites measuring only several inches in any dimension and very light. The CSXT(Civilian Space eXploration Team) launched their new “GoFast” rocket on July 14th to an confirmed altitude of 73.1 miles or 385,800 feet. (rocketry.wordpress.com). 73.1 miles is an impressive distance to achieve by hobbyists. The shortest distance between Earth and space is about 62 miles (100 kilometers) straight up, which by general accord is where the planet's boundary ends and suborbital space begins. Space for orbital things generally begins at 100 miles, and low earth orbit at 120 miles.


To be able to launch a payload into orbit a rocket would need to accelerate the payload to thousands of miles per hour horizontally and reach orbital altitude. The hobbyist rockets usually have several cameras and appear to have enough power to increase the payload. Most of the high altitude hobby rockets use a solid fuel that is cast into a mold. The fuel is the heaviest component to a high altitude rocket. Some amateur rockets use liquid gas fuels like liquid oxygen and a liquid fuel. The liquid fuels add additional levels of complexity (and cost) to a rocket project. Some liquid fuels require very cold temperatures etc. The benefit to liquid fuels is they may have more energy density, but are immensely more complex.


How much larger would the rocket need to be to be able to launch a cube-sat micro satellite into orbit?  This would account for the need of multiple stage rockets that separate from the main rocket. A cube-sat satellite is also much lighter in weight than payloads of larger rockets. A cube-sat might weigh a total of 0.5-20kg.


Most amateur high altitude rockets do not have stabilization including rotation prevention. Stabilization enables the rocket to make adjustments to ensure the rocket does not go off path. This also prevents high spin rates. In some of the amateur rocket videos the rocket spins so fast that the video is blurry. Stabilization could prevent this type of spin. A stable rocket is necessary to deliver the payload into orbit without any spin.



An example of smaller rockets that could achieve orbit are the S-Series fleet of sounding rockets funded by the Japan Aerospace Exploration Agency (JAXA) that have been in service since the late 1960s.

SS-520-4 is the fourth vehicle configuration of the SS-520, and this version includes a small third stage, which can put a 4 kg 3U CubeSat into a 180 km × 1500 km orbit with an inclination of 31°.


SS-520-4 Specifications

    Height – 31 feet (9.54 meters)
    Weight – 2.9 tons (2.6 metric tons)
    Diameter – 20 inches (52 centimeters)
    Payload to Low-Earth Orbit – ~9 lbs (4 kg)



An educated guess on cost for an amateur cube sat rocket would be around 6 figures in costs depending on the size of the rocket and fuel used.

UPDATE:

Space Enterprise at Berkeley is planning on sending a rocket to 135km(~84 miles) and they are doing it with a budget of only  $150,000 - $ 250,000 .

Japan successfully launches world’s smallest satellite-carrying rocket (SS-520)


References:

https://en.wikipedia.org/wiki/High-power_rocketry







Is an amateur cube-sat launch possible? from rocketry

Is an amateur cube-sat launch possible? • r/rocketry from aerospace

Friday, September 1, 2017

Space elevator construction using a space gun orbital delivery system.








Construction of a space elevator would enable mankind to enter into the space age. A space elevator that uses a tether to earth would enable efficient and inexpensive delivery of mass into orbit. There have been several recent designs published that accomplish a space elevator type system. The plan outlined in, "Loaded sectioned space elevator. by Sadov, Yu. A.", the total mass of the elevator is 500,000 t . Using conventional rocket based delivery systems this would be a difficult and expensive task. A space gun firing mass into space is a relatively inexpensive space delivery system per unit weight vs. delivery by rocket burning rocket fuel. Even the SpaceX reusable rocket will not be able to beat the cost per pound of delivery provided by a space gun. A space gun launches a payload at extremely high acceleration rates into space. The high acceleration rates are too great to support passenger delivery into orbit. A space gun by itself is not capable of placing objects into stable orbit around the planet because of the laws of two-body gravitation. Each payload launched from a space gun would need to perform orbital correction/stabilization propulsion to change the shape of its orbit after launch. The space gun could launch a series of payloads into designated orbits. The orbit(s) for space gun payloads could theoretically be precision calculated to avoid other space objects, and maintain a reliable orbit to be collected by spacecraft. The payloads in orbit could be collected and distributed or consolidated by spacecraft capable of flying into the orbits of the space gun payloads and then collecting each individual payload. The payloads could contain resupply/refuel components to support spacecraft. The payloads from the space gun could be collected by drone spacecraft and used to construct a space elevator. September 2012, Quicklaunch was seeking to raise $500 million to build a gun that could refuel a propellant depot or send bulk materials into space. The cost to deliver to orbit would be $250 per pound.


A space elevator could connect tether(s) to a ground elevator infrastructure. The space elevator from that point forward could be used for inexpensive delivery of mass and personnel to and from earths orbit. At $250 per pound the cost to send 500k metric tons into orbit to build a space elevator would be 275,000,000,000 US $. 275 Billion dollars. Not including infrastructure or assembly costs. All these figures are not exact and represent estimations. According to (https://en.wikipedia.org/wiki/Non-rocket_spacelaunch) . A space gun would cost 1/2 a billion dollars to build.  There may be a need to build multiple space guns to accelerate the rate at which one could fire the space gun.








A few different technologies that would accelerate space travel are things like the confirmation and testing of reliable EM propulsion drives. Other important key technologies would be capable of accelerating or transporting passengers faster than the speed of light. The construction of a space elevator would accelerate scientists abilities to develop and test space technologies. The interesting fact is that most of the technologies already exist to be able to begin construction of a space elevator system. The entire project could probably be crowd-sourced and built using crowd-sourced technology. For example the team of volunteers at Copenhagen Suborbitals are making progress on sending a passenger into space on a shoestring budget. We are too often reminded about how small and fragile our planet is. Luckily there is nearly infinite space for mankind to explore. Space is big enough for each person to have their own goldilocks zone planet if they desired.





References:





















Elahi, A. (2010, 02). READY, AIM, RESUPPLY. Popular Science, 276, 32. Retrieved from https://search-proquest-com

Sadov, Y. A., & Nuralieva, A. B. (2015). Loaded sectioned space elevator. Cosmic Research, 53(3), 230-236. doi:10.1134/S0010952515030065

Wednesday, July 12, 2017

SparkFun 0.66" Micro OLED with Espressif ESP32 Development Board using BLE to communicate with Android.



SparkFun 0.66" Micro OLED with Espressif ESP32 Development Board using BLE to communicate with Android. The software for this was created using the Arduino IDE with the SparkFun Micro OLED Library Version 1.2.0 and  ESP32 Arduino library. The Espressif SDK GATT server demo was also used for bluetooth connectivity. I used the nRF connect Android app to test sending data over bluetooth to the ESP32. The oled is connected to the ESP32 via SPI.


Arduino library for the SparkFun Micro OLED
https://github.com/sparkfun/SparkFun_Micro_OLED_Arduino_Library

Espressif SDK GATT server demo
https://github.com/espressif/esp-idf/tree/master/examples/bluetooth/gatt_server

SparkFun 0.66" Micro OLED.
https://www.sparkfun.com/products/13003

Espressif ESP32 Development Board.
http://a.co/bocnGeM

nRF Connect for Mobile
https://play.google.com/store/apps/details?id=no.nordicsemi.android.mcp



Monday, June 19, 2017