PWM output on CNC BOB

[dazp1976]

Net xenable? - that's connected to par-port pin 17.

That'll be why the relay is coming on when steppers asked to move.

[jolyonjenkins]

Ah, thanks. That sorted it

[jolyonjenkins]

I have another problem. When the machine is on, but the computer is off, pin 17 (the relay) goes high and so the relay switches on. Do I need to pull it low?

[dazp1976]

I have another problem. When the machine is on, but the computer is off, pin 17 (the relay) goes high and so the relay switches on. Do I need to pull it low?

If you pull it low the relay will just work backwards.

You should always have Mach pc in control BEFORE you turn on the controllers themselves.
When finished. Turn off controllers first, then shut Mach pc down.

I used to get a relay flicker when powering on the pc, that was when I used usb for my 5v input.
I now use a seperate supply into the 5v & gnd terminals on the bottom row of the board for isolation.

[jolyonjenkins]

I find it a bit odd that it defaults to being high. I'm not sure if it's just floating up or whether this is intentional.
It it's floating, then a resistor ought to pull it down. I can't see that it will make the relay work backwards in any case.
I also use a separate PSU for the logic 5V, not from the computer.

[dazp1976]

I find it a bit odd that it defaults to being high. I'm not sure if it's just floating up or whether this is intentional.
It it's floating, then a resistor ought to pull it down. I can't see that it will make the relay work backwards in any case.
I also use a separate PSU for the logic 5V, not from the computer.

Those relays can be a bit of a chore. I never used it due to hearing it clicking away on startups.
There is a jumper next to the relay, so:
What I did is change the jumper setting so it uses pin17 screw terminal instead of the onboard relay for spindle on/off.
Got a seperate 5v relay with NO/ COM /NC contacts and hi/low trigger option and conect it to pin 17 output.

When PC is off mine sits in NC position. It will not trigger unless it has signal. Spindle switch is connected to NO. It only turns on spindle if Mach activates pin17 via 'spindle on/off'' button. It will NOT come on unless pc is on with mach running.
This will solve the problems.
I actually have a servo drive for mine. It's setup as: Pin17 is my on/off, Pin16 is my direction control.

Relay like this one below.
https://www.amazon.co.uk/Electromech...732588&sr=8-19
You can get them cheaper, this was just for quickness. Made more sense to me to buy multiple channel ones.
Being able to choose between high or low trigger I found quite useful.

Mine is an eight channel module. I have a few things with 5v negative to the trigger (jumper low). Also have a few things with 5v positive to the trigger (jumper high). Everything works perfectly with either polarity acting as triggers (as long as you set the jumper correctly). Great versatile little units :)