Longs 3 axis CNC kits - are they suitable for Bridgeport Series 1 conversion?

**m_c** · 02-11-2018

It's worth highlighting the main reason opto-isolators are added to BOBs is for protection.
Using a parallel port, get something wired wrong, or have something short and connect power to pins they can't withstand, then more than likely your PCs parallel port (and likely entire motherboard) will be dead.

With newer motion controllers, the path of destruction from a wiring problem isn't likely to be as long, but it's still potentially a couple hundred pound controller that could be releasing it's magic smoke.

It's a calculated risk not using them, but at slow speeds, they shouldn't cause any problems. I certainly wouldn't be searching out a BOB without them, unless I was really going to be pushing pulse rates.

Regarding suitable motors.
A good starting point would be to try and find out the torque for the existing motors, or even a datasheet with torque curve (it's surprising what a google for the model number turns up).
You can then run a few figures and see how the various options compare. You'll likely find some suitably geared NEMA23/4s provide better performance than NEMA34s directly coupled, especially when running from lower voltage.

**Boyan Silyavski** · 03-11-2018

I would Not retrofit a precision metal cutting machine with an Open Loop system

, given prices of new cheap servo motors and drives, used servo motors and drives and closed looped steppers which i dont like much pricewise

**john swift** · 04-11-2018

adding more detail to post 7 for any one wanting to use a BOB with opto-isolated outputs and stepper drivers with opto-isolated inputs

the problem with the BOB supplied as part of the kit is ue use of the slow PC817 opto-isolators used for the outputs

I would expect the DM860A stepper drivers would have a PC817 on the enable input and a high speed isolator like a HCPL2531 for the step and direction inputs
as used on this Tormach driver input