View Full Version : 2 Machines 1 Switch for the output - Connections

Ian Hart
01-04-2010, 01:19 PM

Is there any reason that I could not control 2 machines from the same set of drivers by switching the output from one to the other through a serial data switch?
The switch has 9 pin sockets and I'm connecting two steppers, therefore 8 wires through each input. I am aware through previous bad practice that I need to power down the drivers before switching.
Is there also any reason that I need to have connections made to all three outputs whilst operating the system. ( my lathe has 2 axes, my mill has 3)

Ian Hart

01-04-2010, 03:56 PM
Ah, the world of computer communications a la 1960's and 70's. I remember it well.

You might have two problems.

1. Despite the sockets having 9 pins (DB9 I will presume), they might not all be connected. It depends how good the switch is. Basic serial comms only required three lines (Gnd, Rx and Tx) and some switches switched only these.

2. You might have trouble with the current rating. From your description I presume you are talking about the wiring between the drivers and the motors. In which case you are talking about a couple or more amps at tens of volts. Serial comms deals with currents of milliamps. Your switch might simply not be able to take the load. Without either looking inside to see how it is constructed or taking the risk of meltdown it is difficult to tell.

If, however, your switch is a good old mechanical one, similar to this http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3901697 which has DB25 connectors, then you might just get away with it. I would open the lid and take a look inside.

Ian Hart
01-04-2010, 04:42 PM
The switch is mechanical and appears to have all 9 connections. I am, indeed, attempting to switch the connections between the motors and my RoutoutCNC stepper drivers.


01-04-2010, 07:44 PM
You'll have to look inside it. My guess is that it is a multi-pole rotary switch (?) and is probably up to the job. It might have markings with current rating on it or a serial number you could look up. It will then depend on whether the internal wiring is sufficient. It needs to be the same or greater gauge as the wiring that you are breaking into. If not then you could possibly rewire it internally.

01-04-2010, 08:26 PM
I wouldnt trust them switches as far as I could throw it!
I've had several go open on a few pins and boy did it take some trouble shooting to find!
They are not upto the job plus the fact if you forget and switch with power on you could fry the controller best to put plugs on your steppers.


Ian Hart
02-04-2010, 12:14 AM
Thanks for the input chaps. I have put plugs on the steppers but as you probably know it's a pain to keep swapping them but if that's what to do then, better safe than sorry.


02-04-2010, 07:57 AM
Ian,Thats the best bet I dont think you will be swapping with that regularity if you do then eventually buy some more drivers. Better in the long run than buying them because they blew up!!


02-04-2010, 02:33 PM
you could use relays to handle the power switching, and switch the relays