your idea on how to: switch (mosfet?)

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stevech
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Posted by stevech: Thu. Oct 17, 2013 - 03:26 AM
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Modifying an existing digital circuit:

Circuit A: 3V, low-going pulse, 500uSec every 200mSec
Circuit B: 3VDC thought to be sourced by a pull-up inside a microprocessor with OEM part number.

Need: Connect B to A when 3V logic level C is true (could be HI or LO; prefer HI).

When I use a jumper wire, the voltage level of the A:B join doesn't deteriorate the pulse and the effect of doing the connection does cause the microprocessor to take the correct action (change a valve from open to closed).

Constraint: This is all 1yr battery powered so the method needs to consume very little current. So no relay or LED-based opto-isolator will do.

Thanks in advance.

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Learning and Information, General Electronics
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valusoft
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Posted by valusoft: Thu. Oct 17, 2013 - 04:42 AM
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CD4016

Cheers,

Ross

Ross McKenzie, Melbourne Australia

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stevech
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Posted by stevech: Thu. Oct 17, 2013 - 06:11 PM
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thanks...
is there a discrete component single-switch product around? Maybe TO92 or some such?

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ka7ehk
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Posted by ka7ehk: Thu. Oct 17, 2013 - 06:20 PM
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Try single-gate logic from TI, Fairchild, or On. Pretty sure there are some analog gates in a nice little SOT23 package.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Chuck99
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Posted by Chuck99: Thu. Oct 17, 2013 - 11:31 PM
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stevech wrote:
is there a discrete component single-switch product around? Maybe TO92 or some such?

Try BS108
A will pull B low, only when C is High.

Attachment(s): 

Image icon N-FET Circuit.png
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stevech
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Posted by stevech: Fri. Oct 18, 2013 - 06:53 AM
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thanks guys, a zillion.
The BS108 looks promising.

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