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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

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Computer Interface Circuits

 

12v to 19v Laptop Power Supply (Concept)  -  Concept Only.  I have a big screen HP laptop computer.  The large brick size AC to DC power supply is rated at 19.2v and 9.5 Amps, which is about 180 watts. Id like to be able to use the thing in my car.  I looked into a 12v car adapter for it but never really found one that I liked.  Most were underpowered. The other option was to use the existing AC to DC adapter and run it off power from a 12v to 120vac inverter . . . [Circuit by Dave Johnson P.E.,  07/26/09]

 

Computer Controlled Power Relay  -  Often there is a need to turn on and off a 120vac device using a low power +5v logic signal from a computer.  The circuit below shows how this could be done.  The circuit uses a power relay with a 120vac coil and 10 Amp contacts.  A small solid state relay turns on and off the relay.  The solid state relay provides 5KV isolation from the computer . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/31/11]

Laptop Power Supply  -  Concept Only.  I have a big screen HP laptop computer.  The large brick size AC to DC power supply is rated at 19.2v and 9.5 Amps, which is about 180 watts. Id like to be able to use the thing in my car.  I looked into a 12v car adapter for it but never really found one that I liked. . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/26/09]

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