Gecko G540 and Coolant Control Relay

[MrAR15]

I'm in the process of hooking up my relays for the spindle off/on and the coolant off/on. I have reviewed the Gecko wiring schematics but i can't figure out one thing.

The Gecko G540 can control up to 2 relays using pins 5 and/or 6 as well as pin 12 being the GRND. Do I need to provide a separate power supply within that little circuit to activate the relays or does the G540 provide that power through pins 5 or 6 to the relay when the appropriate software command is issued?

Regards
John

[Jeff-Birt]

Pins 5&6 provide the DC 'ground' (common) when that output is turned on. You need to have the +side hooked up to the other side of the relay. If you are using lower voltage relays you need to power them with a lower voltage supply as shown in the gecko docs.

To make it easier on folks using a single 48V supply I just started carry a 48VDC relay kit. It comes with the relay and terminals to hook it up.

http://cnczone.com/cncparts2.aspx

[MrAR15]

Originally Posted by Jeff-Birt Pins 5&6 provide the DC 'ground' (common) when that output is turned on. You need to have the +side hooked up to the other side of the relay. If you are using lower voltage relays you need to power them with a lower voltage supply as shown in the gecko docs. To make it easier on folks using a single 48V supply I just started carry a 48VDC relay kit. It comes with the relay and terminals to hook it up. http://cnczone.com/cncparts2.aspx

So the G540 is only acting as a computer controlled switch in this particular circuit. It would have been nice for the G540 to also supply power to the relay as it has 5v available from the host computer and all it would need to do is route that power into that side of he switching operation. But then I know nothing about electronics so there must be a reason that this can't happen or they would have already incorporated it into the design of the G540.

Never the less, I'll order two new relays from your web sight. That seams the easiest route rather then having to install another power supply just to deal with the relays.

Thanks Jeff

Regards
John

[SpeedsCustom]

Thanks for posting this. I tried to set up my coolant relay with my Gecko on my Taig Months ago. But whenever I used my Physical E-Stop (Also using EMC2) my coolant would turn on.

M8/M9 work, but when ever the e-switch was pressed! The Gecko goes into Fault and relay turns on. I need to change my HAL file.


I really need to get around to this!


-Jason

[Mini Beast]

When I bought my electronics from Jeff, one of his recommendations was to put the e-stop on the power line going to the power supply. I think that would ensure all your relays are "off" when you hit the switch.

[Jeff-Birt]

So the G540 is only acting as a computer controlled switch in this particular circuit. It would have been nice for the G540 to also supply power to the relay as it has 5v available from the host computer and all it would need to do is route that power into that side of he switching operation. But then I know nothing about electronics so there must be a reason that this can't happen or they would have already incorporated it into the design of the G540.

Internally the G540 converts the motor supply voltage to 12VDC and uses that for all the other on-board stuff. There is no extra current available to drive other things like relays though.

You did ask a great question about why it would be set up this way though. The short answer is flexibility. Many machines will have a separate power supply for things like indicator lights and such, maybe something like a 12V or 24V supply. The 'Switching to ground' scheme lets these types of machines use the same types/voltage of relays powered by the same power supply as the other auxiliary devices. So it does not tie you into using 5V or 12V or what ever relays, you can use the style that best suits your needs.

Electronically speaking 'switching to ground' (called active low) is very, very common. The way transistors are constructed the types that work in this manner are easier to construct, handle more current, are easier to use, and they are less expensive too. It does kind of seem backwards at first though.