Teardown: Solar Powered Ultrasonic Dog Repellent

In this teardown, we examine the innards of the solar-powered ultrasonic dog repellent, complete with solar panel and PIR sensor.

A Cursory Look

The Instecho's solar-powered ultrasonic dog repellent is designed to use ultrasonic signals to repel animals away from yards and outdoor spaces without bothering nearby humans. The device is triggered via PIR sensor and has a solar panel attached.

It's a rather small unit, measuring only 5.9(W) x 3.3(D) x 14.5(H) inches, and has the following advertised features:

• Power supply: rechargeable batteries with solar panel
• PIR sensor
• Ultrasonic frequency: 18-40 KHz
• Low power consumption:
  • Standby = 0.8mAh
  • Working = 15mAh
• Coverage area: 2425 square feet (@ 30 feet)
• Weatherproof: works all year round
• Will not harm humans or animals

Instecho's solar-powered ultrasonic dog repellent. Image courtesy of Amazon.

First Impressions

Four small screws hold the two plastic halves together, and the plastic halves definitely don't provide a "weatherproof" seal—weather "resistant" would be a more accurate term. Nonetheless, once the plastic assembly was opened up, I was very surprised to see the simplicity of the electronics system. 

First look inside the assembly.

The solar panel—which generates ~9.5V in bright sunlight—is glued to the top plastic half.

Solar panel glued to the top of the assembly.

Judging by the internal assembly the manufacturer placed an emphasis on cost reduction—perhaps that's the reason for this unit's low price of $20-30 (at time of purchase).

The image below displays how both the LED lens and the speaker are "welded" to the plastic enclosure by way of, as a guess, a soldering iron. It appears an iron was used to simply, and quickly, melt the plastic pieces together.

Although this welding method seems to be successful, it's not aesthetically pleasing and it makes servicing these components very difficult, if not impossible. Then again, at its price tag, probably no one is going to service this unit.

Speaker and LED lens are cheaply welded to the plastic enclosure.

Finally, Amazon's reviews are clearly cut and dry: buyers either really like this unit or really dislike it; there aren't too many reviews in between these extremes.

The Innards

The internal components consist of:

• Two PCBs:
  • The main PCB contains all the system's intelligence
  • The second PCB is a very simple PCB used solely for the fastening of the three white LEDs
• Speaker: This is the advertised ultrasonic frequency speaker, and appears to be extremely cost effective (AKA cheap)
• White LED protection lens/holder
• Ni-MH rechargeable battery pack
• Cable assembly to the solar panel

All the internal components (aside from the white LED lens and the solar panel because it's glued in place) were removed from the plastic assembly and are shown in the image below.

Internal electrical components.

The PCBs

As previously mentioned, the white LED PCB is very basic. In fact, it contains no components besides the three LEDs. Therefore, it makes sense that this PCB should be made as inexpensive as is reasonably possible.

PCB for the three white LEDs.

The other PCB, the one that contains all the smarts of this ultrasonic dog repellent system, is still a rather simple design concept:

Main PCB (bottom side).

The main PCB looks like an average basic design: it's a double-sided design, meaning there are no internal layers—this is an ideal approach for reducing costs.

Although there's nothing too exceptional about this PCB, I did notice that EMI countermeasures are absent. This is a bit surprising, especially given the fact that a microcontroller is utilized in the design. On the other hand, the plastic assembly contains no FCC compliance or other EMC marking labels, which suggests that EMC testing was not completed on this design (not good) meaning EMI countermeasures were never considered.

The components on this board include:

• LDO Voltage Regulator (3.3V): Advanced Monolithic Systems AMS1117. This device is available in either voltage-adjustable or fixed-voltage variants. This design uses the 3.3V fixed-voltage version and provides all the necessary power required for this board. The regulator is powered from the battery pack and/or solar panel.
• Microcontroller: Microchip's PIC12F510 8-pin, 8-bit Flash MCU provides the "brains" of this design. When this microcontroller detects a signal from the PIR device (discussed below), the three white LEDs are flashed on and off and the ultrasonic speaker is activated.
• Schottky Diode: This SS14 Schottky diode allows current to flow only from the solar panel to the battery pack/voltage LDO regulator.
• NPN Transistors: These two transistors, both driven by the microcontroller, serve as the "switches" for turning on and off the speaker and the LEDs.

Flipping over the main PCB (shown below) allows us to inspect the following components on the opposite side:

• Electrolytic Capacitors: These are garden variety electrolytic capacitors ranging from 10uF to 22uF. All three are rated at 25V.
• Inductor: There's not much to report on this component. Only unintelligent markings are listed on this passive part.
• PIR Sensor: This AS412 PIR (passive infrared) sensor is referred to, by its manufacturer, as a type of intelligent PIR due to its integrated "digital control circuitry and body sensitive element in one electromagnetic shielding" device. More so, its delay timing parameters are controlled from externally-placed resistors. Given these features, it appears this PIR sensor is extremely simple to incorporate and to use in one's design.

Main PCB (top side)

Conclusion

As I mentioned before, this solar-powered ultrasonic dog repellent system is extremely simple in design—it's much more elementary than I imagined it would be. And although neither robustness nor quality appears to be near the top of the priority list, cost reduction seems to be right at the top. This system gives the impression that it's worth the (low) asking price.