!!!!!!!!!!!!!!!!!!!! IMPORTANT !!!!!!!!!!!!!!!!!!!!
The TinyCNC-II has NO current sensing circuity whatsoever! This was done to keep the design and assembly as simple as possible. With this in mind, the process of performing the measurements described in the manual, in order to set the proper values to limit the stepper motor current, is the responsibility of the user. Please pay particular attention to Section 3.13 “Current Strength/Speed Correction Entry” as well as Section 3.15 “Chop Delay Value Entry” and make sure that you understand these sections. Without doing this, the user runs the very real chance of destroying (or considerably shortening the life of) your very expensive stepper motors (Ask me how I know this)!
Next, the user must remember that the TinyCNC-II can be build in 2 configurations.
1) The first configuration is with the 2 watt 1K resistor (R54) jumpered out. This configuration is intended to run with power supply voltages from 12 to 32 voltages. So 100 watts (transistors wattage limit) divided by 32 volts is 3.125 amps max.
The flyback diodes across the transistor outputs are rated for 2 amps so it is not recommended to exceed this limit though each phase by much more then that. So, 32 volts x 2 amps equals 64 watts per phase. Well within the 100 watt limit of the Darlington transistors.
2) The second configuration is with the 2 watt 1K resistor (R54) installed. This configuration is intended to run with power supply voltages from 32 to 60 volts. This second configuration has high enough wattage being dissipated across the 100 watt Darlington transistors that the user must pay close attention to the wattage (current x voltage) of your system. Running at 60 volts implies each transistor can only pass 1.667 amps max!
So, even though the power transistors have the ability to pass 4 amps, the user must not exceed the 100 watt limit of the Darlington transistors or the 2 amp current limitation of the flyback diodes in order not to burn them out and damage your stepper motors.
Finally, as currently designed, the TinyCNC-II is not sealed and so is NOT resistant to liquids and chips. The user must position the unit far enough away from the machine tool to keep it dry and free from debris. In addition, the TinyCNC-II unit controls reasonably stout motors at respectable feed rates. Safe shop practices MUST be followed to avoid injury. Always keep one hand on the emergency shut down button and maintain a safe distance from the machine tool during ALL movement operations. Every attempt has been made to design and test the TinyCNC-II in order to provide a safe and useful tool. But, like any machine, the TinyCNC-II could fail. The TinyCNC-II is targeted at the experienced hobby machine shop user that is familiar with appropriate cutting speeds, feeds and shop practices. There is great risk in exceeding the capability of the tools you are using and can result in tool damage and/or personal injury. Do not use this product unless good manual techniques and safety practices have been developed.
!!!! Use this controller at your own risk !!!!