Brent Benade
New Member
I have the following challenge and would like to discuss options and work on a possible solution.
Infrastructure:
6-8 CNC machines that can accept code via a parallel port interface
2 Windows 7 Pc's with multiple serial ports used to send data to the above CNC machines
3 Lathes
1 Windows 7 Machine multiple serial ports to send to the Lathes above
Each device has a Null modem with loop back handshaking cable connected to it and runs back to the main office where it is manually connected to the Pc's and changed when each machine needs to be used.
Project scope:
Design a switching panel that accepts an serial input from each of the 3 computers (possibly 4 for future growth but not critical)
Manual selector switch that connects the input signal to the correct output device without interference on any other output device.
Thoughts and designs:
Rx,
Tx,
Ground
Range of +3 to +15 volts or the range −3 to −15 volts
Seeing that the RS-232 Null modem cable with loop back handshaking only uses 3 wires to communicate first line of thought was on a 3 pole 8 selection switch per input. Thus each of the 8 devices connected to 2x 3 pole 8 selection switches and each switch connected to the 3 pins of the RS232 to the input device. The challenge here could be, if Computer A is sending data via Switch A to device 3 on selection 3 and then Computer B wants to be connected to Device 4 on switch B. Switch B could connect to Device 3 for a moment while turning the selection switch to get to 4. Might cause data interference. Or if both selection switches were left on the same selection.
Thus they would have to be segregated that no connections could be made except to the desired selection.
First looked at relays but too complex and not cost effective 3 n/o 2 n/c Relay per 4 pole selector switch.
Then 3 transistors per device line with each B pin of each group of 3 transistors connected to a 1 pole 8 selection switch.
Thus when the selection switch is on lets say selection 2 it connects a trigger voltage to the transistor group that connects E to the output of Device 2 while all other group on C are still connected to the Serial port but with no output connections.
The same solution can be duplicated for the Lathe machines on a smaller level or added for a possible 4th programming computer.
I know this is a very crude and rough thought idea, but this is why I am asking for some advice or an easy way to solve this problem.
Cables are constantly broken by manually switching the device and large Serial Switching devices are very hard to find and proves to be fairly costly. Then where is the fun in purchasing something then you can make it. ;-)
Thanks for any help in advance
Infrastructure:
6-8 CNC machines that can accept code via a parallel port interface
2 Windows 7 Pc's with multiple serial ports used to send data to the above CNC machines
3 Lathes
1 Windows 7 Machine multiple serial ports to send to the Lathes above
Each device has a Null modem with loop back handshaking cable connected to it and runs back to the main office where it is manually connected to the Pc's and changed when each machine needs to be used.
Project scope:
Design a switching panel that accepts an serial input from each of the 3 computers (possibly 4 for future growth but not critical)
Manual selector switch that connects the input signal to the correct output device without interference on any other output device.
Thoughts and designs:
Rx,
Tx,
Ground
Range of +3 to +15 volts or the range −3 to −15 volts
Seeing that the RS-232 Null modem cable with loop back handshaking only uses 3 wires to communicate first line of thought was on a 3 pole 8 selection switch per input. Thus each of the 8 devices connected to 2x 3 pole 8 selection switches and each switch connected to the 3 pins of the RS232 to the input device. The challenge here could be, if Computer A is sending data via Switch A to device 3 on selection 3 and then Computer B wants to be connected to Device 4 on switch B. Switch B could connect to Device 3 for a moment while turning the selection switch to get to 4. Might cause data interference. Or if both selection switches were left on the same selection.
Thus they would have to be segregated that no connections could be made except to the desired selection.
First looked at relays but too complex and not cost effective 3 n/o 2 n/c Relay per 4 pole selector switch.
Then 3 transistors per device line with each B pin of each group of 3 transistors connected to a 1 pole 8 selection switch.
Thus when the selection switch is on lets say selection 2 it connects a trigger voltage to the transistor group that connects E to the output of Device 2 while all other group on C are still connected to the Serial port but with no output connections.
The same solution can be duplicated for the Lathe machines on a smaller level or added for a possible 4th programming computer.
I know this is a very crude and rough thought idea, but this is why I am asking for some advice or an easy way to solve this problem.
Cables are constantly broken by manually switching the device and large Serial Switching devices are very hard to find and proves to be fairly costly. Then where is the fun in purchasing something then you can make it. ;-)
Thanks for any help in advance