without the USB cable supplying the 5V to the breakout board
if any of the printerport input pins 10 ,11 , 12 , 13 or 15
can supply enough current ( a standard TTL IC its input terminals can source1.6 mA from its +5V supply )
current will flow into the breakout board pin and via the first 74HC14 IC's input protection circuit to the +5V printed circuit to power the other IC's and the power indicator LED
normally I'd connect both the USB and the LTP printer cable before switching on the PC
I use a separate power supply to 5V via USB. In my tests, everything is plugged in, then I turn on the BOB and then the PC. I noticed that the PC also fed the BOB after completing my tests, when I turned off the BOB and the PC.
I'll try to use diodes but I currently lack the equipment for it and I'll buy diodes, DB25, board, etc.. I am interested to know, but I'll need a more practical, so I will also try to replace this card.
I will update this thread as soon as i'll receive the diodes.
John, I want to thank you for your help.
NB : i'm not sure about the diodes because even when the BOB is unplugged from the PC, all the pins 10, 11, 12, 13 & 15 are set to 5V when only one input is closed.
I'd assumed the PC USB port was supplying the breakout board and not a mains PSU
the only advantage with taking the power from the PC is the breakout board is switched on and off at the same time as the printer port cicuit
It looks like you have a problem with the breakout board or the limit switch wiring .
with only the 5V supply connected you should have 0V between the ground terminal and the printerport connector pins 10 , 11 , 12 , 13 ond 15
since the inputs are pulled high by resistors and the output of a
74HC14 inverter is connected to the printerport
( only 1/6 of the 74HC14 is used in each of the 5 input circuits )
connecting a wire link between ground and the Estop should only make pin 15 switch from 0V to +5V
connecting the A axis input to ground should only make the printer port pin 13 switch from 0V to +5V
the X , Y and Z limit switch inputs should control only the corresponding pins
10 ,11 and 12
removing a link or opening a switch should only make the corresponding printer port pin switch from +5V to 0V
once you have used wire links at the terminal blocks and proved the breakout board is working
you can repeat the tests with the limit switches and machines wiring
have anybody make or orden 3 axis 7-segment display and hand jog box to hy-jkm5/hy-jk02-m board, i has try google search many day but no found, were can buy or schematic how build own dispaly to 3 axis display and hand manual jogging box encoder hand wheel and buttons. but no found anywere how connect display and were orden ? working fine my cnc whit hy-div 268n-5A tb6600 drivers.