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  1. M

    Help designing a PWM w/ 19.5 Vin and 12 Vout

    Thank you so much for your help. This is my first project that I'm doing solo. I'm amused at how much I felt like I was learning in my undergrad, and yet how confused I am now that nothing is handed to me. :) (My degree is in physics, not electrical engineering.) Back on topic: I understand...
  2. M

    Help designing a PWM w/ 19.5 Vin and 12 Vout

    OK, I've drawn up a sketch. I can wire the resistor and LED in parallel and then put the LM7812 in series with the PWM loop. Will I need to worry about heat in the LM7812? It will be constantly ... shunting(?)... the excess voltage to ground, right? Also, I've found another circuit diagram...
  3. M

    Help designing a PWM w/ 19.5 Vin and 12 Vout

    Here is a link to the source with a 12V VCC to the 555 timer, as a reference. This is the only design I've seen which allows for 12V to pass through the 555. Still, I desire to use a 19.5V source. I would like to know how to modify this design to accommodate...
  4. M

    Help designing a PWM w/ 19.5 Vin and 12 Vout

    I'm new here. First post. Please advise if this thread is in the wrong place or if there is any problem w.r.t. forum guidelines and rules. I'm building a variable speed motor controller. I have a brushless DC motor (12V @ 180 mA). It's a 110 mm computer fan, re-purposed. I have a DC 19.5V...
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