MIcro Mill CNC Controller

This was to be the controller for the XYZR table using the HobbyCNC board.  Since bad cabling and a wire scrap managed to blow up two of the driver chips, I decided not to use the board for the XYZR table and go with an older, but more replacable design.  To be completely accurate in all matters, this was not a fault of the HobbyCNC board, but was due to the mysterious "things that happened".  The only fault that I would have on this board is that it's easy to blow up chips with a wire scrap and perhaps a bad cable.  That's a problem with the existing SLA7062 chips, and not a problem with the newer generation of chips.

However, replacing those chips allows me to consider the controller for use in the micromill.  All I think I need to do is to wire the motors to the board a lot better.

 
So this is the controller design.
Front view.  The outlet is controlled by the spindle relay, and the pilot light is on when the spindle relay is on.  (117vac)
Back view.  The HobbyCNC board is to the left.  The fan is in the middle.  The relay breakout board is next to the right, and a nice industrial style plugin relay is to the far right.  The terminal strip is the power supply input.
Close up of the board.  Sadly the two vertical chips to the right mounted on the heatsink are no longer with us.  The 24 volt output is used to run the fan and the relay board.  The regulator does not get hot with the minimal load on it.  The large black object the right bottom is a blade style fuse holder.  As I said, the thing I don't like about this board is that it is not optically isolated.  I'll be fixing that.
Closeup of the fan.  I had a dead IBM PC power supply.  The fan worked, but the supply was questionable.  I was thinking of ways to mount the fan, when I realized that I had the perfect mount.  I simply cut a piece of the original power supply case, drilled two holes in it, and that's the fan mount.  The large piece of aluminum is the heatsink on the driver chips.  It's not really needed, but I figured that it would be a good idea anyway.
The relay board.  The big heatsink is overkill, but the one that I am using on the XYZR table's controller will not be running a fan.  All it will be doing is running the chips on the board and providing power for the spindle relay.  The relay in this one only draws 50 ma, so that's minimal.  The board will provide a way to combine all the optical limit switches into one line, and will also supply power for all the LEDs on the optical interruptors.  The TIP-120 is run in saturation and doesn't even get warm at 50 ma.  It can, however, run heavier loads.
24 vdc coil (from the fan supply) and socket.  Note the coil supressor diode at the bottom.  117vac wiring is not in at the moment for the arms, but the relay's contacts are otherwise wired.  The outlet and the pilot light were not made for 0.125 thick aluminum and the little plastic ears would not grab the panel well.  I cut some islands into the back to thin the panel at a few places and it works just fine.  The pin connectors on the relay board pick off pins that are unused on the controller board.
A better shot of the relay board.  Pins 14, 16, and 17 are not used but are available on the HobbyCNC board.  They fit a 0.200 pattern.  The board here uses 0.100 for the connector, then adds a jumper to control the transistor.  The next incarnation of the board has smaller heatsinks, because it's not running a fan.  I need to go get more of those screw terminal strips.
That's it for this installment.  The wiring is kinda obvious, and the function of the chips is easy enough.  The 74LS32 takes all the normally low optical interruptor outputs and combines them.  Any one going high is a limit going high.  The 74LS04 is used as an inverter and LED driver.  The LEDs are on there just for a warm fuzzy feeling to know that the thing is working.
More to come, mostly wiring on the mill and then some ideas of how it will work.