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Baby-O with voltage divider at VIN causes very low voltage


#1

I designed a PCB with a place to solder in a Baby-O. I included a voltage divider at VIN to lower the voltage going to VIN (it will be powered by 12V car power). After populating the PCB, I tested it using a 12.15V wall wart. The Baby-O did not light up so I measured the voltage at VIN and found it to be 1.92V (I expected around 9.3V). When I connect the power supply directly to VIN, it works fine. What is wrong with the circuit?

Sorry the circuit is hard to read. Please let me know how to do the image properly. (I deleted the circuit drawing)


#2

Hello.

The formula for a voltage divider relies on the load pulling a negligible amount of current. If the circuit you constructed to run off the voltage divider pulls an appreciable amount of current, then the voltage divider formula is invalidated. Accordingly, voltage dividers are not an appropriate circuit for providing power.

You might consider using one of our switching voltage regulators to supply an appropriate voltage to your Baby-Orangutan. If you want to use a regulator and you let me know how you plan to use your Baby-O (e.g. how much voltage you want to supply, how much current you expect your system to draw, etc.), I could help you narrow your search.

-Zach


#3

Thanks for the quick reply.

As it was tested it probably drew in the milliamps - whatever the Baby-O draws on its own. Even when combined with the elements the PCB is designed to control, it will draw a maximum of 200 mA at less than 6V using one of the motor controllers.

I bought one of your regulators and it works fine with the system. I got the D24V22F9, it allows 2.3A - much more than I need but I like the margin of safety. This will be powered by an automobile “12V” electrical system and thus can provide an input voltage of around 14.5V plus.