Did you try building the relay blinker from last weeks email? Here's another simple blinker circuit.

This one has no moving parts and is based around a logic gate:

The yellow triangle is a NOT-gate, like the ones found in the CD40106 chip.

It needs to be a Schmitt trigger NOT-gate, meaning that the threshold for going from 0 to 1 on the input is different from the threshold for going from 1 to 0.

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Here's how it works:

When the voltage across C1 is low, the NOT gate sees it as a LOW signal on the input, and inverts this to give a HIGH on the output. If you power this with 9V, HIGH means about 9V.

So the LED is on.

But the 9V on the output will also create a current back through R1, through the capacitor C1, and down to ground. When there is current through a capacitor, it gets charged, and the voltage across it increases.

When the voltage across the capacitor reaches a certain voltage, let's say it's 8V, the input to the NOT gate is considered HIGH, so it switches it's output to LOW.

That turns the LED off.

And you get current flowing in the other direction. Out from the capacitor, through R1, into the output of the NOT gate. So now the capacitor is discharging, and the voltage across it decreases.

When the voltage across the capacitor reaches a certain voltage, let's say it's 1V, the input to the NOT gate is considered LOW, so it switches it's output to HIGH.

And we're back to where we started. The process repeats. So you get a blinking light.

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​Choosing component values

To get the lights to blink about once per second, use a 100 μF capacitor (C1) and 10 kΩ resistors (R1 and R2).

That's a high resistance for R2, but it ensures you don't pull too much current out from the IC. And it's usually enough to get a dim light from a standard low-power LED.

If you also want to control the blinking speed, replace R1 with a potentiometer.

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This is a simple oscillator circuit and is a really good building block to learn.

You can use this for a lot of things like creating sound, making a clock, a timer, a synthesizer, a light show, and much more.

Learning electronics is about understanding the basics, learning building blocks, and practicing enough to understand how to tweak things and create new functionality based on the building blocks you know.
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Keep On Soldering!
Oyvind @ build-electronic-circuits.com

PS: If you're looking to advance your electronics knowledge, here are two ways I can help you on your journey:

• ​Getting Started With Electronics​ is a short and beginner-friendly eBook I wrote to help people get started. It contains clear and simple instructions to get started building electronics. Perfect for complete beginners.
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• ​Join Ohmify: Ohmify is for enthusiasts eager to dive into electronics, offering training in soldering, circuit design, Arduino, and more – all while building hands-on projects.