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Author Archives: R-B

Another RPi-based solar powered weather station

Posted on August 18, 2016 by R-B Leave a comment

Brian Masney from Morgantown, WV has designed a full-featured solar powered weather station that includes sensors for measuring rain, wind, temperature, humidity, and pressure. It runs on a Raspberry Pi Zero running the latest Raspbian Testing Lite and is powered by a 6600mAH 3.7V lithium ion battery that is charged using a 6V 9W solar panel.

Solar powered weather station

The solar panel is attached to the top of the project box using several large pieces of Velcro. More information about the solar setup can be found on Adafruit’s Website. Be sure to connect the PowerBoost 1000 to the battery charge output pins; not to the load terminal. This is because the solar panel can put out 6V however the PowerBoost can only accept a maximum input voltage of 5.5V. See this post on the Adafruit forums for more details. There should not be anything hooked up to the load terminal on the charger. I fried a Pi Zero and a PowerBoost 1000 on a bright, sunny afternoon with the PowerBoost hooked up to the load terminal.

To reduce the power usage of the Raspberry Pi, the LED and display on the Pi was disabled. powertop --auto-tune was used to enable other power saving features. See the files systemd/power-savings.service and bin/power-savings for details. The power requirements could be reduced even further by desoldering the various LEDs on the solar charger and PowerBoost 1000.

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Open Indirect Ophthalmoscope is a portable screening device for retinal diseases

Posted on August 11, 2016 by R-B Leave a comment

Ebin Philip is participating in Hack A Day Prize 2016 with his Open Indirect Ophthalmoscope, which is an open source, affordable, and portable screening device for capturing quality retinal images.

Open Indirect Ophthalmoscope

Diabetic Retinopathy is a complication of diabetes causing damage to the retina, eventually leading to blindness. The cost of state of the art retinal imaging devices required for identifying this disorder lies in the range $10,000 – $25,000. This makes them inaccessible for the population in rural areas or developing countries. We aim to develop a device under $400 which can provide reasonable quality retinal images to clinicians.

Currently there are over 422 million people worldwide suffering from diabetes. 28.5% of them suffer from Diabetic Retinopathy(1) . 50% of diabetics are unaware about the risk of losing their vision(2). The number of cases of diabetic retinopathy increased from 4 million in 2000 to 7.69 million in 2010 in US alone. Early detection and Treatment can help prevent loss of vision in most cases.

Detection of Diabetic Retinopathy, requires expensive devices for Retinal Imaging , even the cheapest of them costing more than $9000 each. This makes good quality eyecare, expensive and inaccessible to the less privileged. The key idea in the development of OIO(code-named Project OWL) is to provide an affordable solution to help identify DR and hence prevent cases of “avoidable blindness”.

Arduino waveform generator

Posted on August 11, 2016 by R-B One comment

joekutz built an arduino waveform generator using a 8-bit resistor ladder DAC and can output sine, sawtooth, and triangular waveform with frequency ranging from 1 Hz to 30KHz.

Arduino waveform generator

This is my arduino-based waveform generator using a 8-bit resistor ladder DAC. It runs with a sampling rate of 65536 Hz and can create any (whole-number) frequency from 1 Hz to 30ish KHz in sine-wave, sawtooth, triangle and different ratios of square wave.

My generator produces an amplified signal and also a unamplified, high-quality signal. There is a LCD built in that shows the current frequency, and also a speaker. The LCD is actually a hacked cheap pocket calculator, for which i found out how to press CE, +, = and 1 with the arduino to make the LCD show a specific number. Yes I know that this is a stupid hack :). The generator runs from a 9V battery. Two videos are shown below; one for the hacked calculator display and one for the generator itself.

Find details here!

Making a simple ESP8266-based clock synchronized to NIST server

Posted on August 2, 2016 by R-B One comment

Internet has made it quite easy for computers to synchronize their clocks to an accurate clock value generated by a remote server. In the United States, the National Institute of Standards and Technology (NIST) provides official time. NIST disseminates the time using several methods, which include broadcasting over short-wave and long-wave radio, telephone dial-in services (ACTS), and Network Time Service (NTS) over the internet. This article describes a ESP8266-based clock project that utilizes NIST’s NTS service to retrieve accurate time information and display it on a 4-digit seven segment LED display. The time is synchronized to the NIST server after every 2-minute interval. The display also contains a colon that blinks every second.

ESP8266 seven segment LED clock

MAX7219 serial seven segment displays for ESP8266

Posted on July 28, 2016 by R-B Leave a comment

Seven segment LED displays are brighter, more attractive and provide a far viewing distance as well as a wider viewing angle as compared to LCD displays. The major drawback of using seven segment LEDs is they are resource-hungry. Our MAX7219 based serial seven segment LED display modules allows you to add 8 digits of seven segment LED displays to your microcontroller project using only 3 I/O pins, and provides full control of all the digit segments including decimal points. You can even cascade two or more of these modules together without sacrificing any extra I/O pin.

Since it requires only 3 I/O pins, this display module can also be used with low pin-count microcontrollers (such as PIC12F series). Visit my MAX7219 tutorial page for more detail on MAX7219 and PIC12F683 interfacing example. With Arduino, it can be easily interfaced using the LedControl library. Check out my example on using this module with Arduino.

ESP8266 and MAX7219 seven segment display

Since the LedControl library does not utilize any hardware specific functions of Arduino platform, it is compatible with ESP8266. What this means is you can easily interface these displays with any ESP8266 module and use the LedControl library to program it using Arduino IDE. You can download my demo example from the following link.

MAX7219_7SEG_NodeMCU

This example uses NodeMCU board for illustration. The NodeMCU pins used are D8, D7, and D6 for driving DIN, CLK, and LOAD signal lines, respectively, of the serial seven segment module. Although, MAX7219 is designed for +5V supply, I have used it several times with 3.3V output signals without any problem. But I do connect its VCC to +5V, even the serial data and clock lines from ESP8266 are 3.3V.