{"id":96,"date":"2022-01-27T00:31:18","date_gmt":"2022-01-27T00:31:18","guid":{"rendered":"https:\/\/paulcarbone.com\/50days\/?p=96"},"modified":"2022-01-30T19:26:35","modified_gmt":"2022-01-30T19:26:35","slug":"day-1","status":"publish","type":"post","link":"https:\/\/paulcarbone.com\/50days\/2022\/01\/27\/day-1\/","title":{"rendered":"Day 1: The Astable Multivibrator"},"content":{"rendered":"\n

How do you blink a light with only discrete components? The Astable Multivibrator, which is a type of relaxation oscillator. ‘Astable’, meaning it’s keeps flipping between two states, and never rests in one (we’ll see this later when exploring the venerable 555). <\/p>\n\n\n\n

We’ll draw this up in a moment, but first lets pick a flashing rate, and see how close we can get.
And again, I’m exploring and winging it in real-time, so I’m going to be wrong<\/em>, but: The time constant is simply R*C, which gets us to 63% of the total charge of the capacitor in the RC circuit. Will this circuit flip at that point? I don’t know! But lets use it as a starting point.
Lets try for a period of 1 second. I’m going to guess that we need a pretty large value of C, and I’m going to pick a standard value, say 47uF. So now we have to calculate the R, given T & C:
R = T\/C == 1\/47e-6 (sorry, that’s horribly formatted scientific notation) = 21,276, or ~22k, which is super convenient, since that’s a standard value as well (huge coincidence, or exactly how the grandfathers of electronics intended?)<\/p>\n\n\n\n

Fun fact: The Astable Multvibrator is the only <\/em>schematic that it’s OK to use diagonal lines for!<\/p>\n\n\n\n

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When wired up, it has a nice symmetry, which is super important in the field of electronics.<\/p>\n\n\n\n

And you’re not gonna believe this, but it worked on the first time. I’m calling that pretty damn close to 1 second period too… so yeah, Day one’s in the bag \ud83e\udd18.<\/p>\n\n\n\n

Video’s on the second pic.<\/p>\n\n\n\n

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A post shared by Paul Carbone (@toomanyoscilloscopes)<\/a><\/p><\/div><\/blockquote>