FAQ about BOBs (Break Out Board)


 



What is a BOB?

A BOB is a Break Out Board.  A BOB typically takes a 26 pin ribbon cable (2 x 13) from a SmoothStepper port and converts it to a more convenient form factor. 

  • Some BOBs provide screw terminals that are directly connected to the ribbon cable input (no electrical modification). 
  • Some BOBs provide screw terminals that have opto-isolation or electrical filtering before it connects to the ribbon cable input.
  • Other hardware (like the Geckodrive G540) are an all in one motor driver with a break out board built in, that connects directly to your ribbon cable.
  • There is another type of BOB that plugs directly into the SmoothStepper.  The C25 BOB (uniquely) connects without any ribbon cables at all, and gives you full access to Ports 1 and 2 on the SmoothStepper.

 



Which BOB should I get?

Arturo Duncan of CNC4PC.com is asked this question quite often. His answer is that choosing a breakout board is much like choosing an automobile. Do you want a 4-cylinder car that gets good gas mileage? Or a pickup truck or SUV for hauling things? Does it need a trailer hitch? Do you want 4 doors? The same applies to CNC. Do you need to drive a spindle motor? Do you need relays for vacuum pumps or coolant pumps? Do you need opto-isolation? You probably don’t need isolators on the step & direction signals if they are driving motor drivers that have isolators on those lines already. The best way to approach this is to make a list of all of the signals that you need to control. If you ask someone which breakout board you should use and you don’t have this list, you’re probably going to get the automobile analogy for an answer.

 



Where do I find a BOB?

We have a list of BOB vendors and there products here.



Connecting to the BOB

The “parallel port” connectors that the ESS uses are the same connectors that PC motherboards use. They are 26-pin low-profile headers that a ribbon cable plugs into. If the ribbon cable has a female DB25 connector on the other end, it looks just like the parallel port of the computer.

The ESS has 3 parallel port connectors, yielding a combined total of 51 I/O’s. The USS has 2 parallel port connectors, yielding a combined total of 34 I/O’s. Some breakout boards use the same connector. In that case you would use a ribbon cable with a 26-pin header at both ends.


Here are examples of various ribbon cable possibilities:
1. 26-pin female header to DB25 female.
2. 26-pin female header to DB25 male.
3. 26-pin female header to 26-pin female header.


Here are examples of various breakout board receptacles:
1. DB25 female
2. DB25 male
3. 26-pin male header.
4. 26-pin female headers.

We sell various ribbon cables and connectors, here.

 



How do I power the BOB?

A BOB or Break Out Board can take 5V power from a SmoothStepper, the BOB can supply 5V power to a SmoothStepper, or the BOB's power can be independent form the SmoothStepper's power.    This depends heavily on the BOB's design and power consumption, so you will need to look at its specifications.  The BOB must use (or supply) 5V power if you want it to share power with a SmoothStepper.

 

Power is transmitted to or from the BOB over a ribbon cable using Pin 26.  You must use a ribbon cable that has a26 pin connectors on both ends.  A cable with a DB-25 connector on one end will NOT be able to carry 5V power to/from your BOB, since pin 26 is not present on the DB-25 end of the cable.

Parallel Port Pin 26

To connect the power to pin 26, you must place the appropriate jumper on the SmoothStepper.  There is one jumper next to each port, and it only connects power for that specific port.  Here are the links on how to jumper the ESS and how to jumper the USS.   By placing the jumper, it will allow power to flow in either direction for that specific port.

 

The power supply that you use must provide a stable 5V for the SmoothStepper and the BOB.  The power supply must provide enough current to meet the requirements of the SmoothStepper and the BOB when they are operating at full capacity.  If there is not sufficient power during peak demand, logic signals may become garbled -or- communications may drop out -or- the SmoothStepper may reset.

 

Here are links on how to power the ESS and how to power the USS, including how much current each of the SmoothSteppers needs.  Keep in mind that if you are powering your USS via the USB cable, that you will have at most 500mA of current.  If you are using other devices on the same USB hub or a low power hub it can be significantly less than 500mA!  Good external power supplies can be found for less than $10 (or free if using a recent cell phone charger) and can prevent many many headaches!

 

If you are going to use your SmoothStepper to power the BOB, you will need to do the following:

  • Make sure only the SmoothStepper is receiving power from a power supply!  You don't want your BOB and SmoothStepper to both be powered and sharing power (this will prevent them from running at best or burn both boards out at worst).
  • Set the SmoothStepper's jumper(s) to supply power to the BOB through the ribbon cable.  (Have the jumper short out both terminals on the 2 pin header.)
  • Make sure that the power supply can source enough current to satisfy the SmoothStepper's and BOB's requirements, with a clean 5V.  Each individual 5V jumper pin 26 is rated to carry up to 1.8 A to a Break Out Board, but all 3 combined are limited to the same 1.8 A.  If you do this, make sure that your power supply feeding the ESS is able to supply that amperage plus at least 0.5 A for the ESS, and maintain a stable 5.0 V. 
  • A USS (USB SmoothStepper) will require the use of an external power supply (i.e. not powered by the USB cable) if you are powering a BOB.

 

If you are going to use your BOB to power the SmoothStepper, you will need to do the following:

  • Make sure only the BOB is receiving power from a power supply!  You don't want your BOB and SmoothStepper to both be powered and sharing power (this will prevent them from running at best or burn both boards out at worst).
  • Set the SmoothStepper's jumper(s) to supply power to the BOB through the ribbon cable.  (Have the jumper short out both terminals on the 2 pin header.)
  • Make sure that the power supply can source enough current to satisfy the SmoothStepper's and BOB's requirements, with a clean 5V.

 

If you are going to power your BOB and SmoothStepper independently, you will need to do the following:

  • Make sure that the SmoothStepper's jumper(s) are removed, so that they will not supply power to the BOB through the ribbon cable.
  • Make sure that each power supply can source enough current to which ever device they are connected to; the SmoothStepper or the BOB, with a clean 5V.
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