The illusive Boxford 260vmc

[irving2008]

RTN = return

[Ricardoco]

RTN = return

lol ok so is it supposed to be conected anywhere? ive connected the step to pin 8 on the bob is that the only connection to the speed control board...(i suppose i asked for that lol)

[irving2008]

see my post above... connected to BOB ground alongside pin 8

[Ricardoco]

see my post above... connected to BOB ground alongside pin 8

Thanks Irving, its working now, had to connect the rtn to chassis ground... Next job is put together the TACHO!!! this is just a temporary one as im going to give cash to this person who is designing "The Ultimate Rev Counter"!!:naughty:




Rick

[irving2008]

Thanks Irving, its working now, had to connect the rtn to chassis ground...

That suggests a ground fault... is your BOB optoisolated?

Next job is put together the TACHO!!! this is just a temporary one as im going to give cash to this person who is designing "The Ultimate Rev Counter"!!:naughty:

Lets just see if we can get the project off the ground first.... so many toys to play with, so little time to do so....

[Ricardoco]

That suggests a ground fault... is your BOB optoisolated?
....

Yes it is, its the one from cncdoctor co uk

Lets just see if we can get the project off the ground first.... so many toys to play with, so little time to do so....

Hey ive got the simple one, thats fine, im willing to wait, ive lots of toys to be getting on with too lol

[irving2008]

Yes it is, its the one from cncdoctor co uk

Ah... which position have you got J1 in... are your commons +5v or ground? If you have the commons at +5v then RTN needs to be connected to the -ve (ground) side terminal of the power supply input for the BOB, rather than a general chassis ground...

[Ricardoco]

Ah... which position have you got J1 in... are your commons +5v or ground? If you have the commons at +5v then RTN needs to be connected to the -ve (ground) side terminal of the power supply input for the BOB, rather than a general chassis ground...

I will check in the morning, out of interest does the gnd pin on the BOB go to ground..lol

[irving2008]

depends.... the whole point about an optoisolated board is that it should seperate PC ground (the shell of the D-type and the PC case) from the CNC ground. In most cases they will be at the same potential... but equally they could be several volts apart (for instance if the PC was powered from a different phase of a 3phase feed... not uncommon in factories that derive their 240 from the 3-phase coming in).

The point is, what do you mean by ground? the PC ground or the CNC ground? In this instance the 'common' rail for pins 2 - 9 on the BOB output can either be +5v or 'ground', which is 'CNC_ground' and is the same potential as the -ve side of the external supply to the BOB. Chassis ground could well be PC ground, depending on how the BOB is installed, so if the common rail is not 'CNC_ground' you need to take RTN back to the -ve side of the supply to the BOB and not to chassis ground.

[Ricardoco]

depends.... the whole point about an optoisolated board is that it should seperate PC ground (the shell of the D-type and the PC case) from the CNC ground. In most cases they will be at the same potential... but equally they could be several volts apart (for instance if the PC was powered from a different phase of a 3phase feed... not uncommon in factories that derive their 240 from the 3-phase coming in).

The point is, what do you mean by ground? the PC ground or the CNC ground? In this instance the 'common' rail for pins 2 - 9 on the BOB output can either be +5v or 'ground', which is 'CNC_ground' and is the same potential as the -ve side of the external supply to the BOB. Chassis ground could well be PC ground, depending on how the BOB is installed, so if the common rail is not 'CNC_ground' you need to take RTN back to the -ve side of the supply to the BOB and not to chassis ground.

I think this stems from the fact that the rack system that holds the drivers has the 0v tied to the case, when using the digiplan mod the diagram shows the bob gnd 14,15 connected to the 0v of the driver board... does that sound like the problem...