resistor between bob and driver inputs?

[Aiko]

hi,
I got some parts to start playing with My ims ib106 drives would be damaged by an input of more than 15 ma on the step and direction pins. I have a hubbard cnc breakout board.
Do I need a resistor between my bob and driver?

Thanks in advance
Scott

[Al_The_Man]

You need to know if the Break out board is current limited and/or the voltage supply, for e.g. if 24v and not current limited you would need a minimum of 1.6k, probabally 2k for safety.
Al

[Aiko]

thank you for the reply Al

the voltage supply to the bob is 5v 1 amp wall wort in picture, I have emailed brent at hubbard cnc and will post his respnse when I recieve it. The motor supply is HP 6267b 0-40v 0-10 amp variable rack mount unit from the 70's

[Aiko]

Hello,

Brent's quick response to my questions was "the step and direction signals are direct pass through signals from your computer print port, with no applied modifications from the breakout board other than a relay to interrup the step signals, so there is no potential problem of damaging your drivers."

I am thinking that I do not need any current limiting resistors between the BOB and the Driver as the original IBM specs for parralel ports were 15 milliamps max (and probably less on newer computers). If the breakout board doesn't amplify the current, then I should be "good to go".

Please correct any of my aberant thoughts as I am still a total "noob" to all of this!

[Al_The_Man]

I believe the opto's in the IMS unit do not have any limit resistors so hopefully your printer port can supply the required current to drive them, and does not load the port drivers, detrimentally
I always thought the idea of a BOB was to buffer and/or condition the PC signals, this one apparently just passes them straight through.
As well the IMS unit inputs are sink, which require the port to source, this mode restricts the drive capability further, as the printer port is best used in the sink mode.
Al.

[pminmo]

I suspect you will have to have to utilize some external circuitry as Al eluded to above. Looks like the IMS have a common low side so they will have to have a driver that will source the required current. Many PC's lpt ports won't source the required 15ma. Which leave you needing to provide that extra current via either a buffer IC, or pullup resistors.

[Aiko]

thanks guys,

the drives are available with sinking inputs (ims ib106-s) however the ones that I have (ib 106) do not have sinking inputs. The ideal voltage to the inputs would be about 7 milliamps. I think the minimum that will power the opto-isolators leds is 5 miliamps. I started this thread worried about too much current, turns out I may not have enough I think I might just hook it up and see if it works or not. i sure have alot to learn about electronics.