I have compiled this list of online resources that offer free electronic circuits. The circuits include free schematics and many of them also include explanations on how the circuit works and pcb layout. [Read more…] about Free Electronic Circuits And Schematics Online

# Article

## A Simple Schematic Drawing Tutorial for Eagle

This is my step-by-step guide to schematic drawing in Eagle. Let us say we find the circuit above interesting and want to build a real electronic circuit out of it to test in the real world. The first step is [Read more…] about A Simple Schematic Drawing Tutorial for Eagle

## Electronic Schematic Symbols

To be able to read schematics you must know the schematic symbols. Here is an overview of the most used symbols in circuit diagrams. [Read more…] about Electronic Schematic Symbols

## How To Desolder a Solder Joint

To know how to desolder a solder joint is maybe just as important as knowing how to solder.

Sometimes you need to make a correction to your electronic circuit. Maybe you soldered a diode in the wrong direction or maybe two of your pads have accidentally been connected by some extra solder.

In these cases you need to know desoldering. [Read more…] about How To Desolder a Solder Joint

## How to Use Ohms Law

I usually don’t use a lot of math when doing electronics, but Ohms law is extremely useful!

The law was found by Georg Ohm and is based on how voltage, current and resistance are related:

Look at the drawing above and see if it makes sense to you that:

- If you increase the voltage in a circuit while the resistance is the same, you get more current.
- If you increase the resistance in a circuit while the voltage stays the same, you get less current.

Ohm’s law is a way of describing the relationship between the voltage, resistance and current using math:

V = RI

- V is the symbol for voltage.
- I is the symbol for current.
- R is the symbol for resistance.

I use it VERY often. It is THE formula in electronics.

You can switch it around and get R = V/I or I = V/R. As long as you have two of the variables, you can calculate the last.

## Ohm’s law triangle

You can use this triangle to remember Ohm’s law:

**How to use it:**

Use your hand to cover the letter you want to find. If the remaining letters are over each other, it means divide the top one with the bottom one. If they are next to each other, it means multiply one with the other.

### Example: Voltage

Let’s find the formula for voltage:

Place your hand over the V in the triangle, then look at the R and the I. I and R are next to each other, so you need to multiply. That means you get:

V = I * R

### Example: Resistance

Let’s find the formula for resistance:

Place your hand over the R. Then you’ll see that the V is over the I. That means you have to divide V by I:

R = V / I

### Example: Current

Let’s find the formula for current:

Place your hand over the I. Then you’ll see the V over the R, which means divide V by R:

I = V / R

## How to remember Ohms law

A simple way of remembering things is to make a stupid association with it so that you remember it because it’s so stupid.

So to help you remember Ohm’s law let me introduce the VRIIIIIIII! rule.

Pretend that your driving a your car really fast, then suddenly you hit the brakes really hard. What sound do you hear?

“VRIIIIIIIIIIII!”

And this way you can remember V=RI ;)

### A practical example

The best way to teach how to use it is by example.

Below is a very simple circuit with a battery and a resistor. The battery is a 12 volt battery, and the resistance of the resistor is 600 Ohm. How much current flows through the circuit?

To find the amount of current, you can use the triangle above to the formula for current: I = V/R. Now you can calculate the current by using the voltage and the resistance:

I = 12 V/600 Ohm

I = 0.02 A = 20 mA (milli Ampere)

So the current in the circuit is 20 mA.

If you don’t like calculating things yourself, check out this calculator for Ohm’s law.

### Another example

Let us try another example.

Below we have a circuit with a resistor and a battery again. But this time we don’t know the voltage of the battery. Instead we imagine that we have measured the current in the circuit and found it to be 3 mA (milli Ampere).

The resistance of the resistor is 600 Ohm. What is the voltage of the battery?

By remembering the “VRIIII!” rule, you get:

V = RI

V = 600 Ohm * 3 mA

V = 1.8 V

So the voltage of the battery must be 1.8 V.

## How To Do SMD Soldering Using a Soldering Iron

You don’t need fancy equipment to do SMD soldering at home. You can easily do it using a soldering iron.

SMD stands for Surface Mount Device and they are components that you solder on the surface of a circuit board.

Let me guide you through how to do SMD soldering with a soldering iron.

[Read more…] about How To Do SMD Soldering Using a Soldering Iron