DIY power bank using recycled Laptop battery

This DIY power bank project from Do It Yourself Gadgets uses recycled laptop battery and a 5V boost converter to construct an USB charger.

DIY power bank using laptop battery

DIY power bank using laptop battery

This article will show you the basic powerbank circuit consisting of Lithium cell charging circuit, boost converter and toggle switch as well as my improved version with self activating boost converter and LED status indicator and homemade housing. It all started with an old Lenovo laptop battery. I carefully pried it open to examine the cells. Three packs of two parallel 18650 Lithium 2200 mAh cells were connected in series.

Another RPi-based solar powered weather station


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

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

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

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

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

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

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

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