Finding a useful new resource at

Looking for reference designs and design tools? I was recently made aware of the site. Their front page contains a wide selection of design articles, power electronics applications, and interesting connected hardware projects. Be sure to check them out on your next research dive into your engineering brainstorms.

Solar Power for Africa: Linear vs. Switching

A post on linkedin was posted by a member regarding building a 24W battery charger using an adjustable regulator to do a quick proof of concept PV system for a mini projector in a rural setting in Africa. They were looking for postings that focused on linear design instead of PWM and resonant switching power supply design. So…why do we not use linear regulators?

First of all there are so many simple solar converter circuits out there based on a simple switcher chip such as the TPS54561. Even though solar panels have gotten cheaper it makes no sense to throw away power on a linear regulator in 2015. Here is a link to a product that would easily work:

The efficiency of linear regulators goes down with the difference between input and output voltage. Efficiency for typical linear regulators is usually no better than 70%. Would you want to buy a solar panel that is 30% larger just because you wanted to use a linear regulator?

The most simple charge controllers are based on something we call PWM charging, These units control charging by connecting the battery to the solar panel when the battery needs it and then disconnect it when the battery is charged. As the battery voltage increases, the time connected vs. the time disconnected is reduced until the battery is fully charged.

A better way is to go with MPPT, but that is a topic for later.

A connected home using the photon wifi controller

In my continuing series of web connected objects, I am presenting another post on the internet of things IoT. This presentation is focused on the newest member of the family. As you remember we originally presented a post on the Electric Imp. This is another way to do the same thing. PHOTONDOCUMENTATION

A solar lighting project for the developing world or your backyard.

Have you ever wanted a completely automatic, simple, light system that could be used all over the world for a just few dollars per unit?

This project is a perfect opportunity to learn how to build your own solar power lamp while understanding the components that go into a basic solar system. The presentation presents the components and wiring to a simple solar controller. We use a printed circuit board from another project to provide a landing point for the LED controller. Contact me for any circuit boards, (no controller, you must solder it on yourself), if you send a self-addressed stamped envelope we can send you one for free through USPS!

Solar Battery Light meetup feb18-2015

Solar Battery Light meetup feb18-2015

Beginners Guide to Interfacing Electronics to the Web

Shruti Misra and Dimosthenis Katsis, Athena Energy Corp

The Electric Imp is a powerful module that incorporates WIFI and computer power and acts as a gateway that allows devices to connect to the internet. The Electric Imp has three aspects to it: The imp module, impOS and the impCloud. The imp module consists of a 120 MHz ARM Cortex M3 processor with  2.4 GHz WiFi capability. The processor consists of GPIO ports, ADCS, UARTs etc. The impOS is the software foundation for the imp’s features and provides cloud connectivity for the same. The imp Cloud allow the users to run the ‘agent’- server-side code unique to each imp device.  The agent is used to provide HTTP IO and cloud side processing which allows the device to be connected to any other product(s) with Internet access.

connecting real hardware to the web – using the electric imp

Well Pumps and EnergyBridge

Thanks everyone for your notes and questions about using EnergyBridge on a well pump. Our system is a great way for you to get your power outlets working when your power goes out. In fact you can completely disconnect from the power company if you have enough solar power. Our EnergyBridge system will run lights, a full-size refrigerator, boiler/wood-stove circulator, smaller hand tools, computers, TVs etc. We cannot run the larger high pressure well pumps. For that you will need a separate inverter rated for the pump power you need. Outback power makes a nice 3000W inverter with 220V for a submersible well pump. I would recommend the EnergBridge as your source for solar charging and battery management as well at giving you 120VAC outlet power. The extra inverter should only be used for the well-pump alone. All the inverters can share a common 24V or 48V battery bank managed by the EnergyBridge. Energybridge’s built-in solar charger will keep your batteries topped off without the need to buy extra hardware.

If you run a well pump on an inverter I would also offer that the inverter Remote On/Off signal be connected to your water pressure switch.

Athena Energy has passed Certification

Athena is ETL certified
Athena is ETL certified!

We made it! Athena Energy and our partner PC Precision Eng. in the Dominican Republic is proud to present that our ETL-listed product: the ASI-1000 Grid Tied solar inverter is now available for sale with full UL certification from our factory. The ASI-1000 represents the flagship solar inverter system that is the backbone of EnergyBridge and our rural electrification systems. Please follow us on facebook to see our videos and updates from Athena Energy.

Out of Phase (interleaved) PWM on the Arduino

Out of Phase (interleaving) PWM on Arduino

Recently while designing a charge controller, I needed out-of-phase PWM outputs from an Arduino. Since the timers are linked to two PWM outputs, I thought it would be pretty straight forward. After doing some research, I couldn’t find a simple solution.

While thinking about it, I figured I could offset the timer counter register (TCNTx – where x is the timer number). I thought I might have to change some more register settings to get the PWM between the two timers to match, but that was not the case.

By setting the initial value of TCNT1 to one half of its full value, we easily get out of phase PWM by adding a single line of code in the setup function:

TCNT1=0x7FFF;         //Set Timer1 Counter Register to half of its maximum value (32767)

Here is a scope plot of the output:

And here is the full code for your use:


int PWM1 = 0;      // PWM1 width

int PWM2 = 0;      // PWM2 width


void setup()  {


TCNT1=0x7FFF;         //Set Timer1 Counter Register to half of its maximum value (32767)

pinMode(9, OUTPUT);   //Set Pin 9 to output

pinMode(11, OUTPUT);  //Set Pin 11 to output



void loop()  {

delay(500);            //delay 500ms to see change in PWM

analogWrite(9, PWM1);  //write PWM1 value to output on Pin 9

analogWrite(11,PWM2);  //Write PWM2 value to output on Pin 11

PWM1++;                //increment PWM1

PWM2++;                //increment PWM2



This is useful in many different applications: charge pump gate drivers, h-bridge control, ripple reduction and power handling in power converters.  Since there is a lot of information on PWM for the Arduino, I didn’t go into too much here. Please feel free to ask questions and I’ll do the best I can to answer it!

I hope this helps some people out there!