Quote Originally Posted by EddyCurrent View Post
That would be a sensible solution Jonathan and one that I shall test, thank you
Be very, very sure the BOB output is truely open collector if Vs = 24v or at best it won't work (I'll leave it to the reader to explain why :) ) and at worst you could fry the BOB!

Alternatively make Vs = 5v

Rb for Vs = 5v is 1k
Rb for Vs = 24v is 4k7

1/4w resistors will be fine