/diy/ - Do It Yourself

>>1216917
>my local store does have the 4541
Go get one, no wait, get five or ten. I definitely will because this chip will disappear from the market. My local dealer has it for 0.40 each and 3.20 for ten. Same for the SMD SO14 version.

First thanks to >>1216914 for mentioning the 4541. I didn't know about it and it seems to be the most viable solution for long time delay circuits.

Suggestions to use a huge resistor and a huge capacitor usually rest on the 'threshold' myth. In reality transistors have no threshold, that's just a popular metaphor for what's really going on, i.e. the transfer characteristic. Bipolar transistors have an exponential transfer function and MODFETs have both an exponential (for small currents) and a quadratic one. The transition region between both is what is called the MOSFET 'threshold'. They do not suddenly switch on, especially not when the gate-to-source voltage rises slowly, which is the case for the RC non-solution so many people seem to favor. For a BJT no such region exists and the 'threshold' is totally arbitrary.

Now when you come across a new (for me) component, the Golden Rule is RTFD, read the fucking datasheet. I got mine from https://assets.nexperia.com/documents/data-sheet/HEF4541B.pdf

All you need to know is in there. Basic properties, functional diagram, pin assignment as well as valuable information e.g. about how to calculate the clock frequency/time and (surprise) that the power-on reset function is unreliable for supply voltages below 8.5V. There doesn't seem to be a 5V 74HC version of the 4541 (despite the many bait links google offers).

Diagrams have been posted enough but I'll still draw my own (including pcb), build and test it and file it in my repository of useful circuits.

Today is a good day.