I am working on Roomba and InMoov projects. I needed something to step down power from 12VDC for sensors on InMoov and Step down power from Roomba to EZ B. Thought I would throw this out since there has been a lot of help for me on the Roomba project in the community. I use eBoot Mini MP1584EN DC-DC Buck Converter Adjustable Power Step Down Module
to do both .. very cheap. I buy 6 pack for $9.50 US from Amazon.
The enclosed picture is one installed inside the bottom of a V4 for Roomba. Using this I do not have use an external power supply. 3amp max on these units.
Note You need to adjust before using. On InMoov I use for Ultra sonic sensors connect to V4.
I do not sell but may be useful to someone.