555 timer IC
A lot of projects uses 555 Timer Chips. I saw you can get 20 of them for 71 cents including shipping direct from China on AliExpress. Or 51 cents once the sale starts in two days. https://www.aliexpress.com/item/Original-Texas-Instruments-TI-NE555P-programmable-timer-integrated-circuit-and-oscillator-HYC-3253-h-DIP-8/32308116026.html
"The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two (556) or four (558) timing circuits in one package. Introduced in 1972 by Signetics, the 555 is still in widespread use due to its low price, ease of use, and stability. It is now made by many companies in the original bipolar and in low-power CMOS technologies. As of 2003, it was estimated that 1 billion units were manufactured every year.[5] The 555 is the most popular integrated circuit ever manufactured."