Using 2n2222 to switch relay on/off with 3.3v

[JohnRob]

@Wawa

A safe approach for mass-production?
Hobby-dudes can (should) measure Vce(sat) and can get away, if needed, with maybe 2% base current. I would stick with 5% though.

For quick and dirty testing or circuits I use 10%. For production I would have to know much more about the device.