Delay power on circuit

I am working on a project that uses an analog meter and to give that extra retro feel to it when I turn it on I wanted a delay power on circuit to simulate a tube warming up. I did a quick search and seems everyone uses 555 timers. I know there is a simpler way to do it so I pulled out a book a friend gave me titled “Guidebook of Electronic Circuits” ISBN: 0070404453. The book has 3,600 circuits from the 70s so it should have something. I found the protection circuits chapter and saw one that is meant to protect solid state rectifiers. The circuit uses a 2n3055 NPN transistor a capacitor and resistor. Since I want to use this to switch on a LED that runs on DC current I decided to reverse engineer it and use a 2n3904 NPN transistor, 1000uF 10Volt cap and a 10Kohm 1/4watt resistor. Sure enough it works dandy and with the voltmeter it pushes out 2.65v load with 3.3volts going int the circuit.

Power Delay

Sorry for the crude drawing.

It works very well and you can use bigger or smaller capacitor. The higher the uF the more delay you get.


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