Hi Bert,

I am sorry but I can't write any pro's and cons between the UB1 and the $5 BOB because I don't know the UB1, so I could only compare the specs, which you can do as well. Yes, there are some advantages, but to me they are not relevant and not worth $170 extra. But... CNC Drive have just released a new BOB and that is a more reasonable alternative. If I'd build my machine today I'd probably buy that one. It is a dual port BOB, and it does not seem to have analogue output, so if you plan to control the VFD with 0-10V then you probably need an external PWM card as well. Regardless of which, I think one or two $5 BOB is the way to go for anyone on budget restrictions.

BTW, there is no 25kHz limit, it works just as well with 200kHz also, which is the limit of most of the drivers anyway. 400kHz is the upper limit of the motion controller, but again, with 200kHz you can go very far... The BOB has 74HC14 buffers on the outputs which control the motion through the drivers, so the limit is not the BOB but your drivers. The DQ542MA has a 200kHz upper limit because of the opto couplers on the inputs. I have actually tested them with 400kHz and while they worked well, there is no need for that speed in my machine, so I keep the 200kHz settings.

Also, speed has nothing to do with resolution. The resolution is the same at high speed as it is with low speed.