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Multiple GPIOs to direct different voltage to a single device

jgauthier

Mar 22, 2013
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I need to create a system where I provide a different voltage to a device given a different GPIO output.
Current requirements are not known, but from what I do know about the device it will be very low current.

The idea is this:
1660841746568.png

The problem is that there aren't any power multiplexers available at this voltage range. (No stock anywhere)
So, I am trying to consider ways to reproduce this type of circuit without one.

Could I potentially just do something as simple as this?
1660842085154.png

Utilizing some appropriate diodes? I am not worried about diode voltage drop as the voltages can be within a range and I can control that elsewhere.
 

Harald Kapp

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Nov 17, 2011
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Diodes as shown will not work.

Have you considered using relays?
Either electromechanical ones or solid state ones?

Or simply PMOSFETs with approriate level shifters for the gate-source control voltage?
 

jgauthier

Mar 22, 2013
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Sorry, I don't understand how those would work.
The two triggers are independent. They will switch the 9V and 3V signals (that isn't really shows)

The issue I am trying to solve is getting those 9V and 3V signals on the same line as an input to the device (separately) while also protecting the current flow from one to the other.
 

Harald Kapp

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Like this:
1660920842921.png
A high on GPIO1 activates relay 1, 9V is connected to the output.
A high on GPIO2 activates relay 1, 3V is connected to the output.
Diodes are required only if you cannot ensure that not both GPIO1 and GPIO2 are active at the same time.
 

jgauthier

Mar 22, 2013
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Thank you for the clarification. I should have included a schematic versus a block diagram.
My idea was similar to this one, except for the relays. This makes more sense.
 

Harald Kapp

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Instead of relays you can also use photoMOS "relays" or solid state relays, depending on your current requirements. A photoMOS relay may even be driven by a GPIO pin directly without the need for an additional transistor.
 
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