[GrahamIT]

Hi Graham ,

the breakout boards do work but like the tb6560 boards they do break a few design rules

not connecting a +5V supply to pin 14 of one of the 74HC14 IC's
or not connecting the unused input pin 13 to 0V or +5V - OK for a 7414 but not the CMOS version !!!!
the 1K resistors connecting the 74HC244 output to the boards enable output terinals could be a problem with some stepper drivers


John

I wonder why they connected dir X to both pins 14 and 17?

[john-100]

Hi Graham ,

its my error

when I've copied from an earlier diagram used in post 9 in this thread :-

http://www.cnczone.com/forums/genera...out_board.html

I've typed X dir for pin 17 instead of B dir !!

John

[alcor]

Hello,

I'm not electronics engineer and CNC hobbyist beginner, I'd like to get your advices :

Is this breakout board only able to work with opened circuit limit switches ?
(Is there any workaround to work with closed circuit ?)

Is this breakout board never "resetting" DB25 state after a limit is reached ?
My card is rising state on all input pins - 10,11,12,13,15 - when only one limit is reached and did not release state after limit switch is released.
(Is there any workaround to reset state automatically ? i'd like to use one switch to probe surface).

thanks

[john-100]

Hi alcor

are your limit switches mechanical switches or electronic switches ?
more details of the switch will help

assuming you are connecting all the limit switches to one breakout board input

if they are mechanical switches
you can wire normally closed in series and connected to one breakout board input

the printer port input can only detect when all switches are closed or when the first switch opens

with normally open switches you can wire them in parallel
then printer port input will only detect when all switches are open or when a switch closes

using one input your control software will not know which switch has been operated if more than one axis is moving

if you have normally closed HALL switches (or other proximity detector)
you will have to connect one switch to one input on the breakout board
unless you add some extra circuit

John

[alcor]

Thanks John,

I used common mechanical lever micro switches. I have two normally closed switches in serie per axis at end limits. I have 3 axis so i used 3 breakout board inputs with 1 common ground. I will use another mechanical switch probe connected to A-LIM input for surface probe.
I tested the 3 loops independently (not connected to the breakout board) they reacted as expected.

I'd tested 2 cases :

1/ X Y Z loops are connected as mentionned in attached scheme, A-LIM loop is not present. As soon as i power on the board (Note : i use USB 5V plug to power the board), DB25 voltage on pins 10, 11, 12 are set to 5V. (i didn't tested pin 13). Opening any switch doesn't change anything.

2/ I unplugged X Y Z loops but the common ground is always present on the breakout board GND inputs XYZ. I opened A-LIM switch and then power on.
pins 10, 11, 12 and 13 are 0V. As soon as i closed A-LIM switch, all 4 pins are set to 5V.

Explaining this, I realize that I have not tested if the // cable is involved in the problem ... I'll check this as soon as i can.
Otherwise do i need diode on GND ?

[john-100]

Hi alcor

your connection diagram looks correct

going by the photos of the 5 axis B.O.B. on sale
it looks like there is 2 versions

the version I have tested had no +5V supply to pin 14 of the 74HC14 used in the circuits connecting the E Stop and Limit switches to the PC printer port

without a +5V supply to pin 14 the 74HC14
the E Stop and limit switch circuits depend on power from the printer port
and may not all ways give you valid logic levels

to fix the problem I added the link shown in yellow in the first picture below

with the +5V link added the IC will be powered by your 5V supply
without the board being connected to the computer
you should find when the E stop switch or limit switch is closed
the corresponding printer port pin will be at a logic 1 ( +3V to +5V)

when a switch opens the corresponding printer port pin 10, 11, 12, 13 or 15will be at a logic 0 (0V to 0.8V )



John

[alcor]

Hi,

Thanks for your precious help john.

I checked the parallel cable and all possible ground loops. Nothing to mention.

I added the link on my board and now i have the power led turned on when i plug parallel port on my computer, before 5V USB powered on.
After several attempts, I still noticed that the behavior of the card is as follows (L/S input states) :

1. If all inputs XYZA-LIM & E-STOP are open : Pins 10, 11, 12, 13 and 15 are 2.58 V.

1. If at least one entry XYZA-LIM & E-STOP is closed : Pins 10, 11, 12, 13 and 15 at 5.16 V.

However, i noticed that the behavior is not the same when probing the // port with a voltage meter or computer // port sniffer :
- when using a sniffer : the // port is plugged to the PC and the B.O.B. is not releasing the state when going from state 2 to 1 (see list above),
- when using a voltage meter : the // port is unplugged and i mesure voltage on the connector pins. The board does return to logic 0 when going from state 2 to 1.

I probably have de defective break out board - or a bad designed board, don't you think ? :-)