Thread: What have I done!
I usually get completely the wrong end of the stick but let's have a go.
If you fitted a relay and everything went wrong even after that relay was removed...
This would suggest the relay had no protection diode and what ever you were using to drive the relay also drove the thing that no longer works.
You probably know about protection diodes but just in case. Current flows through the relay coil. A semiconductor device attempts to break the electrical circuit. The coil inductance requires that the current continues to flow, the volts go through the roof, the break down voltage of the semiconductor is exceeded and the magic smoke escapes. A protection diode across the relay coil allows the current to flow back through the coil until it dissipates.
Last edited by Robin Hewitt; 21-02-2016 at 01:30 PM.
Thanks Robin, never heard of protection diodes but there is a diode beside each relay on the power board:
I had taken leads from the coil pins of the existing relay on the underside of the power board to supply my additional relay. Maybe this extra load could overload the circuit, but the relays are still working okay using the manual override switches on the front panel. I didn't notice or smell any smoke at any point. Saying that I was flapping around at this point. Can't see any burn't components anywhere.
Quick question. Does the 25pin port from the PC supply the 5V signals towards the controller only, or does the controller also have to send 5V signals back to the PC. I know that limit switches at least have to send a signal back in some form.
The PP pins send and receive 5v signals depending on the pin. What worries me about this controller is that it has no opto isolation and so your computer is vulnerable. You should be glad that you have a PP card as it is easier to replace than a motherboard. Everything points to a spike going back to the PP. The pinout diagram shows the capabilities of each pin. How they are used depends on the controller. If it were my controller, I would replace the driver board with a BoB and three drivers, but it is a lot of work to cure what could be a simple fault.
It takes all sorts to make a world, I am just glad I am not one of them.
Thanks for that, I am hoping that it is just the PP card. Hopefully I will receive a new one by Tuesday. I remember when I could have popped over to PC world and picked one off the shelf but times seem to have changed.
Replacing with a bob and drivers is my backup plan if all else fails. It is exactly as you put it so well: A lot of work over possibly over a simple fault. If I did end up going that way, with 2 steppers on the X axis, could I get away with 3 drivers or would I need 4?
Sorry, you would need 4 drivers if you have a slaved X axis, I wasn't paying attention to the actuals, just the principles.
What operating system are you using on the PC? Most of these PP cards have very old drivers. They work OK up to XP generally, but no later.
I have got one of the PCI socket (not PCI express) PP cards (dual port) sat in a drawer and several new LPT leads, if you get stuck.
Nick, Maplin used to be good, but it is just a toyshop now. Most of the gear you can get cheaper by up to 2/3 (that's a quarter of the price in pub talk) , though Maplin do take stuff back more readily.
Last edited by cropwell; 21-02-2016 at 05:56 PM.It takes all sorts to make a world, I am just glad I am not one of them.
Thanks Guys and thanks Rob for the offer of the card if I get stuck.
I'm running XP still on the CNC but it's that WinPC-NC Economy that I'm using. The PCI card was churning out 5V.
Hopefully the new card will work and get it up and running, but I know that the old controller isn't the best. I would rather have a seperate PSU, BOB & drivers, so I'm thinking about building a second controller with 9 pin d sub OPs that will connect straight up to the machine and hold it as a backup until I can get time to crossover. I would also prefer to move over to Mach but I'd rather get a bit of practice on it first before going at it full tilt. I can't find anywhere on WinPC-NC to change the axis driver pins to match a BOB if I needed to. Spindle, coolant, tool sensor etc can be nominated but not the essentials it seems.
I just have to wait for the postman now!