CNC

Power, we all think of it as something untouchable, invisible and invaluable and unfortunatly lots of people don't know how to use it.

Really the trick in using power is in the math, if you understand the math you can manipulate power and make it work for you.

So what is power?

Power is a unit of measurement and in the case of Electricity power is defined as Wattage, and Wattage in the form of equation is "P" or Power.

Wattage: Wattage also known as (P) or (Power) is the overall power used, it includes Voltage and Amperage. To determine Wattage this simple equation is used: V x A = P (Voltage X Amperage = Wattage).

Voltage: Voltage is what Drives the Amperage threw the Resistance.

Amperage:

Say we have a 300W power supply, it's rated at 10V and 30Amp, and we have a spindle motor that's rated at 300W, the spindle motor will use the full 30Amp and 10V, however if we connect a power supply rated at 24V 30A, the speed of the motor will increase and the motor will use 24V and 12.5 Amp, leaving some power for something else.

Moving stepper motors.

Say you want to connect three steppers to your milling machine, if the motor is rated at 2.5A the potential draw will be 2.5A x 3, making it important to supply the recommended Amperage or more than the recommended Amperage.

Ohms: Also known as resistance can be determined using Ohms law, you can also determine other things using the same equation "E=IxR", where "E" = Voltage, "I" = Amperage and "R" = Ohms or Resistance.

Given that data, selecting a power supply for anything should be pretty easy.
The next question that comes into play is "how do I obtain a power supply that works for most applications for cheap?" The answer, ATX.
The ATX power supply used in Computer Towers will work wonders for any application and they are inexpensive, you can convert them to work as bench-top supplies for anything your experimenting with and they cost less than $45. USD.
The power needed to run a mill or lathe depends on the motors used.
If the application calls for the use of stepper motors, the power must be DC opposed to AC. The Voltage and amperage required depends on the stepper motor size.
Most DB25 and COM style breakout board, driver board style setups require two power supplies, however USB style Micros only require power to the drivers, the logic power is supplied from the pc threw the USB port.
Some DIY projects only require ATX power supplies, the kind found in old computer chasis, these supplies provide different voltages, generally you see two voltage values, 12V and 5V. These supplies are the best for a person building a CNC for the first time, they have IC's that prevent damage from occuring, the ATX supply will provide you with 120 Watts of power or more for under $40.00, and in some cases the ATX supply will provide over 500 Watts of power. For a pinout
The supply must provide the correct voltage, if the voltage is too high the stepper motor and driver will get warm or produce smoke, generally this is not agood sign. If too little voltage is supplied brown-outs  will occur and things just simply won't work properly.
Amperage can be much much higher than the item requires, for example if you have a 3-amp stepper motor the power supply can be 300-amp with no issues. Wattage is the overall power povided or consumed, and voltage is the force behind it.
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