Additional Modifications & Information

In developing, testing and using the TinyCNC-II, I would, at times, blow out one or two Darlington transistors. This happened when testing new software functionality and/or over driving the transistors with too much current. This occurred most often when testing with the higher voltage/wattage (32V-60V) version of the unit. In order to repair the damage, I found that I had to de-solderer the wires from the  connectors. This proved difficult and error prone. I tried putting the connectors inside the enclosure but the connectors on the motor cables would not fit properly.  So, what I decided to do was to cut 1/8" wide slots from the top of the enclosure down to the top of each connector opening. This made my life much easier when disassemble and re-assembly were required.

As previously mentioned, due to incorrect software settings or too high a voltage setting on my power supply (i.e. testing a 60V TinyCNC-II version instead if the 32V version) or whatever, I have destroyed several of my stepper motors. After the loss of a second stepper motor, I decided that I needed a fail-safe backup method to protect them from my "experimentation" errors.

In the above pictures you will see the 2 amp "BOJACK" fused interface cables that I made for each axis going to a motor. The fuses have a fast reaction time if a 2 amp limit has been exceeded. For my Unipolar motors, I have one fuse per coil phase leading back to the power transistors or 4 fuses per cable. I do not have fuses on the center tap (supply voltage) lines of the motors. These cables have already "saved my bacon" several times.

The picture on the left is the Mill cable connections (X, Y, Z & A) and the picture on the right is the Lathe cable connections (X & Z).

The cables are not hard to construct and are highly recommended in my opinion.

NOTE: The Lathe cables pictured here are shown with a previous revision of the TinyCNC-II unit that has the top (X & Y) and bottom (Z & A) wiring connections swapped from their current revision top (Z & A) and bottom (X & Y) configuration)

The pictures above show an additional "Remote Emergency Shutdown" button that can be built. The button is a simple contact closure button.

Above is a shot of my D.I.Y. liquid cooling setup for my stepper motors. The motor coolant sleeves are PVC tubes cut and bored out to have a 1/8" gap around the motor for the coolant to flow around the motor jacket. Each end is sealed with a properly sized O-Ring in a grove cut into the PVC. The tower consists of 2 muffin fans at each end with the air flow of each fan pointing the same direction (intake on the right and exhaust on the left), with sacrificial muffin fan housings as spacers on each side of the radiator. The reservoir is a PVC tube that has both ends sealed with PVC screw on "End Caps". Inside the reservoir is a small waterproof 12 volt pump  (Model DC30A-1250) with a fine screen intake filter attached. The coolant is steam distilled and reverse osmosis filtered water with an appropriate amount of "Water Wetter" coolant treatment added to help reduce the coolants surface tension to increase the heat transfer efficiency between the motors to the coolant and coolant to the radiator.

NOTE: These picture were taken before the addition of the fused protection cables to each axis.

The 3 oscilloscope pictures shown above show the chopping action of the 3 stepping modes that the TinyCNC-II performs. The Left picture shows "Mode 0" or "Quarter Stepping Mode", the center picture shows "Mode 1" or "Half Stepping Mode" and the right picture shows "Mode 2" or "Full Stepping Mode".

Adjusting the stepping modes (along with the current chopping and speed selection value settings per axis) is useful in optimizing the performance of different motors with differing resistance and inductance values  with different current requirements.

Pictured above are 2 methods of feeding the RPM of the spindle into the unit. The reed switch in the left picture simply feeds directly into the T-Start input and works "OK".  The center optical setup pictured in the center works much better but is more involved to create. This circuit is documented elsewhere on this site or in the TinyCNC-II manual. The right picture shows how I decided to mount my Z axis stepper motor on my mount for the "Constant Force Springs" Z axis head counter balance setup.

As mentioned in the heat-sink modification section, a lot of heat is generated by the Darlington power transistors. To help dissipate that heat, I found that a small muffin fan under the heat-sink really helps to move the heat away.

The cardboard box that I attached the 12V muffin fan to has cutouts on all sides. Its crude but very effective and inexpensive. A larger muffin fan might be even better.

The series of pictures above shows a troubleshooting aid that I have found useful.  On a female DB-9 connector  I have soldered "sniffer" wires to the center ground connection and all of the active signal connections and plugged this into the the Step and Direction connector. With this, you can short between the longer center ground wire to each of the step and direction to see if your motors move in the expected direction, or move at all. You can also use this to test the output signals generated by the "Advanced" programming mode in order to control various external devices.

The series of pictures above shows another useful troubleshooting aid I use. This is a female DB-9 connector with connections soldered to the 4 active motor phase connections and the 2 voltage input connections. These particular LEDs require 7.3K Ohm resistors to get to light up properly when using a 24 volt input power supply. This has been useful in seeing which transistor I might have blown out when my last "experiment" has gone very bad.

NOTE: This video was taken using an prior version of the TinyCNC-II with the upper and lower axis connectors swapped. I have the LED connector plugged into that versions "X" axis. The current versions wiring would place the "X" axis on the bottom connector.

Pictures of previous versions of my 2 Axis CNC controllers.

(For those that might be interested)

Pictured above is the very first 2 axis controller that I created. This controller could only control speed and direction on each axis. I called this controller a "Tadpole" as the Sherline single axis "Frog" controller was my inspiration to get into all of this in the first place. I was using $5 variable reluctance motors at the time.

Pictured above is the 2 axis predecessor to the first generation TinyCNC 2-axis controller. This controller could move programmable distances at programmable speeds on each axis and that was about it. I still used the variable reluctance motors as I was too cheap at the time to buy real unipolar stepper motors.

Pictured above is the first generation TinyCNC controller. This was still a 2 axis controller and had 80% of the functionality of the  second generation TinyCNC-II 4 axis controller discussed on this web site. I finally broke down and bought nice 200 step unipolar motors for this unit to control. This is the unit I tried to sell on EBay but I could not make it inexpensive enough to break even. At this point I was using terminal strips to hook up the external connections to the motors and such.