Solar Serenity

We live in a small river town 70 miles south and two counties away from Chicago, IL. There is an abundance of wildlife here, including a very large number of beautiful birds. We’ve come to enjoy watching the birds feed on the bird-feeder from our breakfast nook in the mornings. There are also rabbits, raccoons, snakes, deer, swans, pelicans, owls, butterflies, dragonflies, falcons, hawks, and squirrels. Yes, squirrels – legions of squirrels. One day, we counted seven squirrels roaming around our front lawn alone. We believe it’s the giant 120-year-old Oak trees, rich with acorns, which they sometimes use to attack unsuspecting guests like bombs falling from a B52.

The other reason for the proliferation of squirrel battalions is the lack of real predators. Our dog is a rescue, and not very ferocious. I think she believes herself to be a chicken, having been raised on a chicken farm.

There is one predator we’ve observed – the Red-Tailed Hawk (see video clip below). Although this Hawk failed to get its prey (don’t worry kids, little squirrelly escaped), it scared away all squirrels for almost an hour from the bird-feeder.

Squirrels can climb up the thin pole, jump onto the bird-feeders from the tree at impressive heights and rip the bird-feeders apart to get to the seed, scaring away all birds. These squirrels even chewed through a garden hose for water. I tried many bird-feeders. Family gifted us with “squirrel-proof” bird-feeders. When the third or fourth one failed to keep the gangster squirrels at bay I decided that I could not be the only person in the world at war with the squirrel. This is the 21st century and someone figured out the perfect squirrel proof bird-feeder.

When I saw the clip above, I was sold. Not only would it keep the squirrels away from the birds, but it would provide hours of amusement if they tried.

The Yankee Flipper (https://www.perkypet.com/droll-yankees-yankee-flipper-squirrel-proof-bird-feeder-yf) runs on a lithium-ion battery (and what doesn’t these days?), that powers a weight-activated spinning perch. A fat squirrel activates the motor and spins them off. It works with 100% accuracy and is made of heavy-duty powder-coated solid metal components (more about this later).

One squirrel, let’s call him Vicious, not understanding why his personal diner wasn’t working for him, tried it four times until he finally gave up. Once the squirrels realized the free buffet was over, and birds recognized it as a safe haven, there was three months of a wide variety of birds from cardinals, blue jays, green wobblers,?to orange orioles, swallows and even woodpeckers.

After the three months, one morning, while sitting at the breakfast nook I glanced out the window and saw Vicious on the perch gorging himself on bird seed. The battery charge was exhausted. How did he know?

There was no low battery light, SMS message or email alert that it was time to recharge the battery. I immediately pulled it out of operation and removed the battery module. Instructions stated that only the official Yankee Flipper battery charger must be used indoors for no more than two hours.?Since I’ve done various projects for work and home involving lithium-ion and even LifePO4 batteries, I understand there’s a need for more intelligence behind charging lithium batteries to insure their long life (up to 10 years of continuous use). As this was in the middle of winter, the requirement for indoors was most likely due to a temperature-controlled environment.

While I waited for the battery to charge, I thought there must be a better way. Converting a bird-feeder into an IoT device with alarm lights and SMS alerting seemed overkill (even in war).

It’s a bird-feeder.

Then I remembered designing and building the 60aH LifePO4 solar kit for my Jon boat’s trolling motor, and the solar-powered flood detector for the cottage, and the designs for a solar computer vision dumpster monitoring kit, or the solar kit for the cloud camera for work (I am infatuated with the idea of free energy). These were all 12V -- was there a way to turn a bird-feeder running on a single 3.7V 18500 lithium-ion battery into a solar powered autonomous robot squirrel-proof bird feeder?

I’ve tested many solar controllers, batteries, and a few solar panels so I did have a couple 6V solar panels in my lab, small enough to install on the top of the Yankee Flipper. However, after examining the top of the unit, that wouldn’t work. As you can see from the photo below, if the squirrels could do that to solid steel, a solar panel wouldn’t have a chance.

After more research, I found a flexible 6V solar panel that I could wrap inside the bird feed compartment, inaccessible to wildlife and the environment, without reducing the capacity of the bird feed (hefty 5lbs). True, being behind the clear plastic would reduce its efficiency, however, we’re talking about 90 days of autonomy, not the standard best practices of four days without sun in our area.

The real challenge was the solar controller. When using lithium-ion batteries, the preferred option would be a MPPT controller. A very simple definition is the maximum power point tracking (MPPT) is a higher efficient DC-DC converter technology, with added intelligence, compared to pulse width modulation (PWM), which is the most popular.?MPPT receives voltage and amperage from the solar panel and converts it to charge the battery at a more appropriate level. It’s not just the PWM on/off, which is why MPPT is better for lithium-ion. We have a 6V 1.2A solar panel that needs to be regulated to charge a 3.7V 18500 Lithium Ion battery, and at the same time, provide enough power to the motor to activate the anti-squirrel perch.

There was not much specification details on the small, printed circuit board assemblies that are the only ones available for 6V. They are actually mostly designed for solar garden lights, providing enough juice for a simple, low wattage LED bulb. First one I tried failed. My only assumption was over-current – the motor needed more power than the solar controller could provide. This was confirmed with my second tested PCBA, which provided an over-current LED flashing alarm light indicator.

Third one was the charm, even included Molex connectors so there was no soldering. All that was left was to rewire the unit and add the new harness and enclosure for the PCBA (so much for my Yankee Flipper Forever Warranty). Modifying and rewiring was relatively simple (see wiring diagram below).

Initial testing has been excellent. The final acceptance testing will be a lengthy one. Will let you know in a few months when the weather gets really hot, and next winter, when the weather gets very cold if it performs as designed.

Meanwhile, I’m going to figure out how to have it automatically refill the birdseed.

Solar Controller and Solar Panel: