Thunder Cats are GO!

A bunch of progress has been made since my last post. Two major steps have been achieved .

• Mounting the Gen3 boards
• Wiring the Electronics

Mounting the Electronics
This started with making a template by exporting the layers out of Eagle to a dxf file and then took that into my CAD program where created the board arrangement. I used some glue stick and pasted it to a piece of plywood and cut it to size.

I made some home made standoffs from drywall mollies. I used some washers to get the desired spacer length and cut them with some good size wire cutters.

Here is a driver board with the standoffs. Also you can see that I added the right angle headers for the opto endstops. I didn't bother taking out the CAT5 connectors.

I had a nice hefty bracket for mounting large curtain rods and  used it to mount the electronics board. I wanted to make sure that the electronics were off the bench so the machine does not take up so much room. All but the power supply is off the bench and I am working on getting that mounted some how.



Wiring the Electronics
Here are some notable points I had for the wiring:

• I unsoldered the molex connector pulling the pins out one at a time and soldered in screw terminals for hooking up the stepper motors.  Digikey: A98168-ND TERM BLOCK 4POS SIDE ENT 3.81MM
• I found some sprinkler wire at a home center to hook up the stepper motors. It worked out great. It is multicolor 18AWG solid core wires with 7 wires in the bundle and has black PVC sleeving.
• I wired up the opto couplers and with Red (+5V), Black (ground) and yellow(signal). This wire was connected to 0.1" female connectors. (Digikey: S7001-ND CONN HEADER FEMALE 3POS .1" TIN) on both ends. 
• I used right angle 0.1" spaced header pins on the driver boards that are right underneath the cat 5 connectors. I didn’t bother to remove the cat5 connectors since they were not in the way.

At this point the McWire is completely wired and ready for action. The next steps are firmware installs, softwares and then printing!

Starting at 0,0,0

So I have decided to take on the project of building a McWire in order to RepStrap up to a Mendel. I'm starting to gather parts so I can start and hopefully finish building the majority of the structure over my Christmas holiday. Until then I have set out to study the various electronic set ups. All seems pretty straight forward. I did, however, find a small mistake on the PWM Driver 1.1.

In reviewing the schematic, I have found that the free wheel diodes seem to be connected incorrectly. The free wheel diodes are D1, D2 and D3 that are the 1n4004. These diodes are used to deal with inductive loads. Inductive loads such as a relay coil will want the current to keep flowing until the inductive energy within the load is dissipated. These diodes, as hooked up now, are not creating a path to deal with this energy. If an inductive load is used, most likely there will be a large voltage spike on the collector of the TIP50 transistors. V=L*dI/dT so the faster it is turned off, the higher the current or the larger the inductance the higher that spike will be.

If noise has been an issue for your system or your burning up PWM drivers this may be a major contributor.

I would recommend moving the diode or adding an additional diode. The hook-up would be anode the the TIP50 collector and cathode to Vss.

The existing diodes are fine where they are but aren't really doing anything.