PRT-08376 USB breadboard power supply - Redesign

Archive New Product Ideas
1

Guys, I think the PRT-08376 USB breadboard power supply

design is a bit kludgey/klunky in that it is too easy to accidentally short it out

and could use a redesign.

As it is, I would never buy this power supply and would

not recommend it to novices.

So why not make it work just like the non USB based version?

(With an added enhancement to access both voltages)

In other words add a second switch the board just like

the non USB based version that switches an the output

voltage from between the 3.3V voltage regulator output and

the 3.3V voltage input. That way you can now switch

between 5v or 3.3v and power a power rail just like the non USB version.

You’ll also need to move the LED power pin from the output of the 3.3V

regulator to the output voltage selector switch/output voltage pin.

Also, a second big improvement/enhancment (and this works for both boards)

would be rotate the two “unused pins” 90 degrees,

and make them source voltage supply pins.

Now you can plug the board in to bottom of a bread board, and

have the switchable voltage power the power rails, and also always have

easy access to the source voltage as well.

It provides a nice consistency to the products.

This also eliminates the goofy problem of shorting the 5V voltage on the USB power supply.

Nice simple, clean and both supplies could work exactly the same.

— bill

2

Just a quick followup for another design feature.

It should also be possible to put in a dual color LED so that the color

of the LED would change depending on voltage selected.

You should be able to take a common cathode bi-color LED

(one with 3 pins):

  • cathode

  • color 1 anode

  • color 2 anode.

Hook up color 1 anode to the 3.3v regulator output.

Hook up color 2 to the voltage switch/voltage output pin.

The magic is in the selection of resistors on the anodes.

If you connect color 2 anode to the center of an appropriate voltage divider

(2 resistors) instead of single resistor, color 2 LED will only light

when the voltage is set to the 5V position.

You end up with color 1 on all the time and color 2 only on

when the 5V selector is switched.

So now you have an LED that is color 1 in 3.3v mode and color 3

(combination of color 1+color2) when 5V is selected.

This would work well with a read/green LED as that could give you green

for 3.3v and amber for 5V.

— bill

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