Sunday, September 23, 2018

Binary Resistance Decade Box

I built this project in June of 2013 and posted it on Instructables


Binary Resistance Decade Box

I've been an electronics hobbyist for many years, so I've used and even built my share of resistance decade boxes. Each one consisted of rotary switches with labels identifying a different power of 10 for each switch. You "dialed up" the desired resistance by turning the appropriate knobs to add up to the target resistance value.

Well, I'm also a computer geek, so I got the crazy idea to build a decade box using DIP switches (instead of rotary switches) and binary values (instead of decimal values). Each switch represents a power of 2 and the resulting resistance equals the combined value of the "ON" switches.

Since binary DIP switches are more difficult to read on site than rotary switches, I decided to include two sets of binding posts; one set to attach to an ohmmeter (to verify the selected resistance value) and one set to put the resistance in-circuit. A DPDT switch lets you toggle between them. Also, since the combined analog resistor values tend to vary from the perfect digital values you want, I added a 25 ohm POT for fine tuning.

This project uses two 8-channel DIP switches, which provide the following binary values: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1,024, 2,048, 4,096, 8,192, 16,384, and 32,768. With it, you can combine switches to create any value between 0 and 65,535 ohms.

As is customary with binary numbers, I started with with the least significant digit (lowest ohm value) on the rightmost switch and increased in power-of-two increments to the maximum value on the left.

Saturday, September 22, 2018

Solar Shrub II

I built this updated project in April of 2013 and posted it on Instructables


Also mentioned on

Solar Shrub II

It's been almost a year since I posted the original Solar Shrub on Instructables. It was a great success from the standpoint that it did what it was supposed to do (charge small devices using nothing but energy from the Sun) . Plus, winning the grand prize in the Green Tech Contest was definitely an ego boost! But there were several specific problems with the original design:

1. Low Current: The current produced was too low to charge some devices in a reasonable amount of time. I harvested the original cells from solar garden lights and the specs were quite a bit lower than I initially thought.

2. Intermittent Charging: Because it was generating power real-time and feeding it directly to the USB port, the charging capacity was only at its maximum when it was in direct sunlight. If a cloud passed over, or the cells were shaded even temporarily, the voltage dropped below 5V and the device stopped charging.

3. Difficult to Assemble: My strategy for the original project was to build “stems” with solid-conductor wires reinforced with wire clothes hangers. These stems were then pushed though holes in a base, bent to 90 degrees, and tie wrapped into place. This turned out to be extremely difficult to assemble, the stems were not as flexible as I would have liked them to be, and I had no easy way to replace a bad stem if needed without completely disassembling it. Plus the solder joints between the solar cells and the solid conductor wires tended to break easily because the wire was too rigid.

4. Vulnerable to Weather: One of the first questions I got about the original project on Instructables was, “Is it waterproof?” My answer was no, but it got me thinking. What if the it was outside charging and it started to rain?

So with these problems in mind, I set out to design a better version!

Introducing Solar Shrub II


Higher Output Current - I achieved higher current by purchasing 8 high-quality solar cells rated at 2-volt x 80mA. Then, with help from Joshua Zimmerman at, I added a USB booster and internal lithium battery.

Combo USB Boost + Lithium Charge Controller + Lithium Battery - The combo board boosts the voltage from the cells to provide a steady 5V to the USB port. It also charges an internal lithium battery which supplements the cells when they are not in full sunlight. Once the battery is charged, I can even carry the device indoors for charging devices in the comfort of my home!

Pluggable Stems - In order to make the stems more flexible and replaceable, I decided to use stranded wire instead of solid conductors and attach the stems to the shrub base using 1/8" phono plugs and jacks. Now I can easily plug and unplug the stems as needed for quick and easy assembly and/or replacement.

A Sealed Water Resistant Enclosure - Instead of building this version into a flower pot like the original design, I built this one as a self-contained plastic “capsule” with all the electronics safely inside. The stems plug into jacks on the top of the capsule which also contains a USB cable with female connector. This design allows weather protection and much more portability. It can be placed into any flower pot or container you wish.

Thursday, September 20, 2018


I built Fijibot in June or July of 2012 and posted it on InstructablesI later posted it on Let's Make Robots, which recently became RobotShop.



Fijibot is an autonomous, self-charging photovore. I built him using a 1.5 liter Fiji Water bottle, an Arduino Uno, 6v solar panel (plus various other parts) from Radio Shack, an Arduino Proto Shield (plus various other parts) from Adafruit, and the wheels and steering arrangement from an RC car.

I decided to use a Fiji Water bottle as the robot's exoskeleton because Fiji Water is an environmentally conscious company and Fijibot recharges its batteries via a solar panel. Plus, I think the round-edged rectangular shape and the (see through) clear bottle make a really cool looking robot!

The Arduino code is posted on Instructables along with the project

Wednesday, September 19, 2018

Solar Shrub

I built the original Solar Shrub in July of 2012 and posted it on Instructables


Won the Green Tech Contest

Solar Shrub

I call my creation the "Solar Shrub". It's designed to resemble a round-leafed plant in a flower pot, but unlike a real plant, this one can charge my iPod, iPhone, and any other USB chargeable device!

I used eight 1.5 Volt round solar cells (leaves) attached to shrink-wrapped wires and clothes hangers (stems) to create an array capable of producing 5 Volts at about 300mA. I wired two sets of four cells in series (to get the voltage) and then wired the two arrays together in parallel (to get the current). I stabilized the power by building a 5 Volt Regulator circuit, then added an on/off switch, power LED, and female USB connector.

Tuesday, September 18, 2018

Motion Sensitive LCD Real-Time Clock/Alarm/Timer

I built this clock in July of 2012 and posted it on Instructables 

Motion Sensitive LCD Real-Time Clock/Alarm/Timer 
I needed a clock for my home office (where I spend weekend mornings building robots and such) and I wanted it to fit in with the decor of my electronics work bench. I decided to build one with all the "guts" exposed. The specs were:

- Real Time Clock
- LCD Display Date and Time
- Include Minute Timer (for timing things while building projects)
- Include Alarm (to remind me I've been in here too long)
- Motion Sensitive (save power by turning off LCD when I'm not in the room)
- Look Cool on my work bench!

The Arduino code is posted on Instructables along with the project

Monday, September 17, 2018

Leo (the robot)

I built Leo in March of 2012 and posted it on Recently, they merged with and Leo is still there.



Why Leo?
I decided to name this robot Leo in honor of one of my heroes, Leonardo da Vinci. Plus, I thought it was a really cool name for a robot! 
I wanted to build an autonomous roaming robot that avoids objects using an ultrasonic sensor. I also wanted it to be small; something that could roam around the house. I've built several kit bots before, but this time I wanted to build something completely from scratch using inexpensive parts and my own ideas.
Leo navigates around a room autonomously avoiding walls and other objects.
  • Actuators / output devices: 2 x Parallax Continuous Rotation Servo and one standard 180 degrees servo.
  • CPU: Basic Stamp 2
  • Power source: 9v battery for logic and 6v battery pack for servos
  • Programming language: Parallax Basic
  • Sensors / input devices: Parallax PING))) Ultrasonic Distance Sensor
  • Target environment: indoors mainly, relatively flat surfaces