555 odd duty cycle

190

01:33:42

Another circuit that doesn't work!! or should I say it all works except the relay.... is there an issue with relays here??

http://www.electronicecircuits.com/electronic-circuits/timer-with-on-off-delay

published 10 years ago

PHAZEFLUX

10 years ago

well seeing as how you don't have the relay hooked up to anything it won't work

PHAZEFLUX

10 years ago

I got your circuit working I'm about to rebuild it and post it

ggundap

10 years ago

Your transistor is not biased properly as it is not going into saturation. The relay needs 12v to operate. Since the transistor is working in active/cut off region the voltage across the coil is less than 12v. In this case the transistor is dropping only 0.8v across the coil. Change the base bias resistor or/and increase the beta of the transistor.

razzle308

10 years ago

@phazeflux. The relay will still operate. Thank for your post but the circuit is not the same - I can turn a relay on and off with a switch.

razzle308

10 years ago

@ggundap. I couldn't say I understood much of that :-p but the link provided is where i got the circuit from and the various commentors suggest that it worked when they built it..??

razzle308

10 years ago

This all comes of the back of the mosfet circuit i posted that again - works in the prototype I have built but does not work in the simulation.

razzle308

10 years ago

ok so bias resistor is before the gate 10k makes it work. Thanks. Why is it 470 ohm in hte example?? :-( Thanks for the comments.

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