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Inductors 101

eiodotcom —  June 2, 2012 — Leave a comment

Today’s Eio post covers inductors.

What is it?

Different types of inductors

The most basic forms of inductors are tightly wrapped coils of wire, which are used in electronic circuits. Due to the magnetic properties of a coil, inductors are able to store energy in their magnetic fields. In other types of inductors, the coil is wrapped around certain types of core material (most often iron) to increase the inductance of the wire.

If you’d like to understand the process of inductance in more easy-to-understand detail, visit the inductors page on

What is it used for?

Inductors are commonly used in radio frequency devices. They are frequency-specific components, so they help produce or eliminate specific frequencies in a signal. Inductors are make up transformers, which are fundamental components of any electric utility power grid. They are also used as the energy storage device in some switched-mode power supplies.

So check out some of Eio’s popular inductor products:

Toko Choke Coil Shielded 22uH 20% 1KHz 2.21A RDL Inductor

TRENDnet TC-TP1 Net Probe (Amplified Inductor and Tone Probe)

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Relays 101

eiodotcom —  May 23, 2012 — 3 Comments

Today’s Eio post is on relays.

What is it?

A relay is an electromechanical device that uses an electromagnet to open or close a switch. In other words, Chet Walters says “a relay works this way: Your switch ‘turns on’ the relay.  The relay ‘turns on’ your accessory. A relay draws very little current through your switch which protects your switch from burnout.  The ‘turned on’ relay can switch a much larger current and not burn out.”

How a relay works. says there are four parts in every relay: an electromagnet, an armature, a spring, and a set of electrical contacts. In essence, when you turn the switch on, it sends electrical current through the circuit and powers the electromagnet. The electromagnet then attracts the armature which acts as a second circuit and completes the circuit so that the light (or electrical appliance) turns on. When you turn the switch off, the armature retracts and makes the circuit incomplete, so that the light (or appliance) turns dark.

What are Relays Used for?

Relays have many uses. Their primary functions include separating AC and DC currents and multiple switching functions, such as delay or signal conditions.

They are used in many electronic applications, such as domestic appliances, air conditioning and heating, lighting and building control, and automotive electrics.

So check out some of Eio’s popular relays:

Velleman Relay Card with LED light switch indicator

Panasonic Power Relay

Velleman Multifunction Relay Switch (includes timers, switching, flashing, interval, random switching)

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Continuing on in our emphasis at making electronics easily accesible and understandable, Eio presents a non-technical explanation of resistors.

What is a resistor? What does it do?

American resistor symbol

A resistor is an electronic component whose purpose is to “resist” (oppose) the flow of electrical current. Resistors are most commonly used in electronic circuits, which are devices that allow electric currents to flow. says, “because resistance is an essential element of nearly every electronic circuit, you’ll use resistors in just about every circuit that you build.”

Resistance is measured in ohms (Ω), where the relationship between current, volts, and resistance is represented by ohm’s law. PlaywithArduino states that to understand resistance, one must understand voltage and current, as defined here:

  • voltage (V) is the measure of the strength electric charges are attracted between the two points
  • current (I) is the measure of how many electric charges are moving per unit time between the two points.

Resistors dissipate power by resisting or limiting the voltage and thus bring down the electricity flow. If a resistor dissipates too much power, it will burn up. Be sure to check the amount of resistance it can handle, often denoted by 1/8, 1/4, 1/2, 1, and 2 watts.

What are resistors used for?

Xicon 3.3 Ohms 1/4 Watt Carbon Film Resistor

Resistors, according to, are used in the following areas:

  • Plate resistor (usually a load)
  • Cathode resistor (usually for biasing, sometimes a load)
  • Grid resistor (to limit ultra HF response)
  • Screen resistor (to limit screen current)
  • Bias resistor (to keep the grid at a constant DC level, often zero or ground)
  • Voltage divider (to cut down the signal level, particularly in high gain amps)
  • Part of an RC low-pass filter (to both lower the voltage and reduce the ripple in the “downstream” parts of a power supply)

So visit our Eio site for all your resistor needs!


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Here at Eio, we want to make electronics accessible to all people, experts and beginners alike. We resist assuming our customers will possess or pursue a thorough understanding of electronics, which requires us to provide explanations of electronic equipment in easy to understand, non-technical language. So today’s post is an effort to give a non-technical explanation of capacitors.

What is a capacitor? What does it do?

According to Wikipedia, a capacitor is an electrical component used to store energy by means of an electrostatic field. Capacitors have at least two electrical conductors separated by an insulator, the dielectric (see Fig. 1).

Fig. 1 Picture of a capacitor

The conductors are connected to terminals so that voltage can be applied across the conductors.

When voltage is applied across the conductors, an electrostatic field develops along the insulator resulting in a positive charge to collect on one terminal and a negative charge on the other. The electrostatic field is what actually stores the energy by the pulling and pushing forces of the positive and negative charges, similar to how charges within protons, neutrons, and electrons hold atoms together.

If you’d like more technical and detailed information, such as the mathmatical formula for how capacitance works, please go here or here.

What are capacitors used for?

Capacitors are used in the following areas:

  • Energy sotrage – they can store electric energy and be used like temporary batteries.
  • Pulsed power and weapons – they are used to supply huge pulses of current, such as detonators.
  • Power conditioning – are used as reserves for some power sources.
  • Suppression and coupling – used as noise filters and snubbers.

    Makezine’s capacitor bank and charger

  • Motor starters – starting capacitors are capable of starting rotational motions in many motors.
  • Signal processing – used for tuned circuits to read particular frequencies.
  • Sensing – senses changes in the capacitance structure.

DIY Projects

If you’re an inventor at heart, here are some links to fantastic DIY capacitor projects.

Check out a popular capacitor product at Eio:


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