Need help with a circuit

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1moldmaker
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Need help with a circuit

Post by 1moldmaker » Wed Dec 20, 2017 6:11 pm

I am a nubee to electronics, what I am trying to do is when I close the switch D1 will light up and it will turn off D2, but I want to is when I open the switch back up it will D1 will stay on for a couple of seconds then it will turn off and turn on D2 again, is this possible with this circuit?

Thanks
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dyarker
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Re: Need help with a circuit

Post by dyarker » Thu Dec 21, 2017 4:42 am

Put a capacitor across the switch contacts. When the switch is closed D1 turns on, D2 off, and the capacitor is discharged. Open the switch and the capacitor starts to charge. That current keeps D1 lit, though dimmer and dimmer; and D2 gets brighter and brighter. It cannot be "snappy" because the RC time constant curve. 1000uF to 2000uF should give a couple seconds (if I can still do the math correctly :-) )

To get the delay with "snappy" on and off would take 2 transistors and 4 more resistors in a Schmitt Trigger circuit. And the timing capacitor could be smaller too!

Or, use a 555 Timer IC.

Cheers,
Dale Y

1moldmaker
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Re: Need help with a circuit

Post by 1moldmaker » Fri Dec 22, 2017 8:40 am

Thanks for the response, sorry about getting back been real busy, I tried your suggestion an you were right, the switch is slow and it has a delay when it turns back on. Do you have any suggestions where I could find a Schmitt Trigger circuit,

Thanks

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dacflyer
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Re: Need help with a circuit

Post by dacflyer » Fri Dec 22, 2017 12:18 pm

https://www.google.com/search?q=schmitt ... 20&bih=946

eat your heart out... just did a google search ( images )

1moldmaker
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Re: Need help with a circuit

Post by 1moldmaker » Fri Dec 22, 2017 2:35 pm

I did the same thing but I couldn't find any circuits that would turn one light off and turn another light on, Im not really good at electronics, what I was really looking for is that the switch wasn't so sensitive and if there was a split second interruption it wouldn't switch the other light on.

sghioto
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Re: Need help with a circuit

Post by sghioto » Fri Dec 22, 2017 3:36 pm

Schmitt trigger circuit. Two transistors and some parts rearranged. D2 normally on. Press S1 and D2 turns off and D1 turns on and stays on for two seconds after switch is released.
Cheers and Happy Holidays,
Steve G
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Schmitt Trigger N&V.jpg

1moldmaker
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Re: Need help with a circuit

Post by 1moldmaker » Tue Dec 26, 2017 5:18 am

Thanks, This is exactly what I was looking for

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