Know what you need to know about Electronics!

“I’m fascinated with the Electronic Devices that we can mess around with.”  – Gerry Mulligan

Gerry Mulligan, one of the pioneers of music industry in America, and one of the very few people who promoted  live music over recorded one, was fascinated with the possibilities electronics opened up for Music Industry in the late 90’s. If he were to be alive today, he would be thrilled to see the advancement of music just because of electronics, from signal processing to EDM, all became possible because of electronics. But as it was evident from his statement, there are a lot of devices around us, with which we can mess around. But that doesn’t mean we have to.

Here are 5 useful TidBits, which you can follow while working with electronics:

TidBit #1: A good friend never lets his friend use AAA.

AAA batteries have significant disadvantages when compared to AA or 9V cells. They have poor output impedance; therefore, their already limited capacity is made even worse as losses increase with load peaks. From typical manufacturer data, AA capacity is 2.5 times that of AAA. Except in cases where mechanical design prohibits their use, AAA cells should be avoided.

Due to modern low-cost dc-dc converters, it is easy to efficiently generate a 5-V supply from two AA batteries. Or, we can simply choose a variable power source such as Benchtop Power Supply or SMPS Adapter for prototyping and even for low volume products such as Fire Alarms.

TidBit #2: Contain that CHARGE

As we are aware, our bodies can contain and/or develop static charge over the skin in different ways. It could be because of environment, or because of substances we are surrounded with.

While this charge is not dangerous for humans, it is extremely dangerous for electronic circuits and ICs as we are not aware of the magnitude of charge we are carrying over our skin, it might damage electronics around us. So, how to avoid any sort of damage? While working on circuits or around ICs, it is suitable to wear an anti-static wrist strap. An antistatic wrist strap is a key piece of safety gear that helps to prevent the build-up of static electricity near sensitive electronics or other projects where static charge could damage electronics or cause safety issues.  

TidBit #3: Never Skimp on Bypassing — Especially at Low Voltage

Low-voltage battery systems incorporate boost converters to supply system voltages. These converters take constant power from the battery, so when the battery voltage falls, input current rises, which exacerbates problems caused by source resistance. In addition, dc-dc converters take power from the input source in pulses, even when the load is constant.

This dynamic loading aggravates the losses due to battery resistance and other factors that add to input resistance. Because losses through resistors are proportional to the square of current, “peaky” loads waste more power than continuous ones. That is why battery bypassing (with capacitance) is so important in systems that include dc-dc converters. If the current passing through input resistance can be made as close to dc as possible, the savings in consumed battery energy can be as much as 5%.

TidBit #4: Avoid Overdosing on Schottkey

The world needs a perfect diode with a 10-mV forward voltage drop and no reverse leakage. To date, Schottky diodes are the best we have, with a forward voltage drop between 300 mV and 500 mV. Unfortunately, for many voltage selection designs, even a Schottkey is not good enough. If conserving energy is a priority in a low-voltage system, power MOSFET switches should be used instead of diodes. Given SOT devices with on-resistances in the tens of milliohms, MOSFET forward drops are negligible at portable product current levels.

The way to determine if MOSFETs are needed for power steering is to compare the diode or MOSFET voltage drop to the battery voltage and treat this ratio as an efficiency loss. If a Schottkey diode with a 350-mV forward drop steers the output of a Li-ion battery, the loss is 9.7%; with 2 AA cells (nominally 2.7 V), the loss would be 13%. In a low-cost design, these losses may be acceptable, but the cost of a high-efficiency dc-dc converter should be weighed against the cost of the 13% or 9% improvement gained from a steering-diode-to-MOSFET upgrade.

TidBit #5: Use the Right Battery

All portable devices have a pattern of use that customers tend to follow as a result of their interaction with the device. Customer satisfaction (or dissatisfaction) depends largely on how the product fits or conflicts with this pattern. For example, it is a distraction when a product requires a user to be extra aware of the battery.

As we all are aware, alkaline cells are not rechargeable but feature a very low self-discharge rate and low cost of implementation. If power requirements are low, alkaline is a good choice. When operating loads are too great for alkaline batteries, rechargeable batteries are required. The trick is to make the rechargeable battery as unobtrusive as possible.

Another use pattern that sometimes fits NiMH is as alkaline “replacements,” where cells are removed from the device when depleted and then charged in an external charger. This is common in digital cameras, but still has the disadvantage of requiring a lot of attention from the consumer.

Products such as cell phones do not conveniently fit the full charge-discharge pattern. Cell phones are charged regularly but drained sporadically. These products need Li-ion’s higher power-to-weight ratio, low self-discharge and affinity for small charge-discharge cycles. Thus, consumers devote little effort to “battery management” and instead focus on the product.

These are some helpful points that can go a long way when working with Electronics!

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