Problem- Relay control with BOB - parallel port pins are always +5V until CNC software startup

[FXC]

I was trying to make my first "extra" by controlling a water pump (flood) with a relay hooked up to my C10 breakout board. I thought it would be as simple as wiring a N.O. relay to any available output and be done with it.

Unfortunately, all my output pins are set to "1" (+5V) anytime the PC is restarted and so the water pump turns on and pumps like crazy until I enter EMC2 (or Mach3) and toggle the flood control.

I was about to build a negating gate and tell the software to invert the output but I don't think this is the way to go. Please let me know of a simple solution - THANK YOU!

[multiplex]

this is where a charge pump circuit comes into play. Mach outputs a frequency on one of the pins, which turns the power on to the board. This way you don't get any unexpected outputs while rebooting, etc.

I always loved it when i pulled into my driveway, and could hear that my router had been running all day long due to a power outage, or computer reboot.

since you are using a C10 board, you are already familiar with cnc4pc.

http://www.cnc4pc.com/Store/osc/prod...products_id=51

[FXC]

I was afraid that a charge pump would be the only solution. Thanks for the link; though I think the price is a little steep... I need 4 - a little over $100. And besides, it shows it's on backorder as of today (2/8/10).

I'll be looking for alternatives, maybe a multi-I/O unit, but if you readily know of something other than cnc4pc, please let me know. Thanks again.

[multiplex]

i'm not sure you need four, however i haven't implemented one yet.

i'm assuming the charge pump would switch the 5v that is going to the c10 board. therefore, all outputs will be dead.

I usually get some twitching on my stepper outputs too.

[FXC]

That's right, only one is needed, I realized that in the meantime. Still, the ones from cnc4pc are on backorder and I can't find anything anywhere else. It would have been nice if I could just close up my control box and put it away sooner, but if I have to wait it out, then I will.

[Al_The_Man]

This is why you have a hard wired E-Stop!, if the system is off on initialization or restarts, all power devices are off including servo's/steppers and require a manual reset of the E-stop to restart.
This is Standard industrial control practice.
Al.

[Al_The_Man]

BTW, if you need to build a discrete watchdog timer using the Mach charge pump signal, it can be done for a $1.00 or so using a 555 (25¢) timer, the principal has been used for many decades, the timer runs at a frequency of slightly slower than the 12khz Mach signal, if not kept reset by the the 12khz signal, then the timer times out and sets a relay, the idea is to constantly reset the timer if Mach is active.
The 555 applications by Google are endless.
Al.

[FXC]

Originally Posted by Al_The_Man This is why you have a hard wired E-Stop!, if the system is off on initialization or restarts, all power devices are off including servo's/steppers and require a manual reset of the E-stop to restart. This is Standard industrial control practice. Al.

This Taig mill was built 10 years ago when E-Stops were probably not very common practice
I'll give it a shot with the 555, I'm sure I have one around. Thanks!

[Al_The_Man]

E-stop circuitry has been around and mandatory by code on industrial control for many decades now.
Often overlooked or skimped on home built equipment though.
Al.

[marzetti]

Hmmm. The 555 charge pump sounds interesting. Can you point me to a schematic?

[Al_The_Man]

I will see if I can dig one up, in the mean time here is a PDF for general information, the 555 would be used in the monostable mode and the in coming 12khz pulse would reset the 555, (pin 4).
Set the time out to around .1ms.
There is probably more information out there on the 555 than any IC made to date.
This uses the 12khz Mach signal as a Watchdog timer not a charge pump, the technique is different but the results are the same.
Al.

[BrassBuilder]

Originally Posted by FXC Unfortunately, all my output pins are set to "1" (+5V) anytime the PC is restarted and so the water pump turns on and pumps like crazy until I enter EMC2 (or Mach3) and toggle the flood control.

Interesting. Mine does the same thing running under Windows 2000 and Mach3.

I think I bought a charge pump for the system but I never installed it. Might be time to look for it and make that a priority.

Mike