There is something about blinking leds. Numerous projects are created with the 555 timer chip. To continue the tradition I will describe in detail the creation of a 555 astable timer board that was designed in the previous blog post.
After the dry film is applied to the copper layer, it can be etched. There is an option to use ferric chloride (FeCl3), but it can not be reutilised and needs to be disposed. An alternative is to work with a mixture of hydrochloric acid (HCl) and hydrogen peroxide (H2O2), which can be regenerated with air and reused for the etching process.