• Definitions and Algorithms related to electrics on the CNC Workstation.

• Ref. Symbols are in Times New Roman 2 sizes up from smallest. Subscripts are increased one size.
• See: Access database for procedures running the algorithms and for additional information.

Absolute: [encoder] I believe that the encoder for Gecko must be Incremental, not Absolute.

• There are two fundamentally different encoder types; incremental and absolute. The absolute encoder contains a disk with several tracks which carry patterns with increasing resolution in such a way that every position is unique. The tracks are read with the aid of an optical system that converts the pattern into a combination of electrical signals, which can be used as is (i.e. in parallel form) or converted to some standard code for transmission over a serial line.
• Absolute encoders have a unique value (voltage, binary count, etc) for each mechanical position. When an absolute encoder is turned on, the position of an absolute encoder is known (this function resembles a resolver, although the principles of operation have no similarity.)

• Means that the circuit is normally low and is taken high (5vdc, 12vdc etc.?) when the device (switch etc.) has been activated. In TTL circuits, any voltage between 2.4 and 5 volts is called "hi". Logic 0 is a "hi" signal.

• Means that the circuit is normally high (5vdc, 12vdc etc.?) and is taken low when the device (switch etc.) has been activated. In TTL circuits, any voltage between 0 and 0.8 volts is called "'lo". Logic 1 is a "lo" signal.

Amperage: [A]

• Amp is the unit of electrical current.
• Gecko has a 0 to 20 A current limit adjust range
• . To convert from ampere-hours to:
• coulombs, multiply by 3600
• faradays, multiply by 0.03731.
• Circuitmate Readings ~ DC Amperage:
• 10 Amp plug: Voltage is 5.04 V & Resistor is 27 Ohms
• Switch at 200 mA ~ Do not use.
• Switch at 10 A ~ Readout shows 0.18 [ 5.04 V / 0.18 A = 28 Ω]
• Switch at 200 μA ~ Do not use.
• 1 Amp plug: Voltage is 5.04 V & Resistor is 820 Ohms
• Switch at 200 mA [.200 A] ~ Readout shows 06.1 [ 5.04 V / .006 A = 826 Ω]
• Switch at 20 mA [.020 A] ~ Readout shows 6.11 [ 5.04 V / .006 A = 826 Ω]
• Switch at 200 μA [.000200 A] ~ Readout shows 1 ( 00.0 before current connection) [ Value above .0002 A]

Back EMF constant: [K_E] [motor]. It appears that [K_V] is the same as [K_E]

• A measure of the voltage per unit speed generated when the rotor is turning. The magnitude and the polarity of K_E are functions of the shaft angular velocity and the direction of rotation respectfully.
• Example; If the Back EMF Constant [K_E] = 65 V / 1000 RPM, then to drive the motor at 1750 RPM in no-load condition, 114V DC will be needed.

• A testing device for multiple line cables that makes a connection to each line to see if a signal is present. This definition is not be applicable to this application. Change

Current - (I )

• The amount of charge that flows past a give point, per unit of time.
• Gecko says ~ The power supply current rating must equal the maximum current that the motor is expected to run at.

• I think that this is what the Gecko G340 has. See Mach3 manual, section 4.5.2. http://zone.ni.com/devzone/conceptd.nsf/webmain/1455E8C8997702698625685800561E82

• Capacitance is measured in units called FARADS. A one-farad capacitor stores one coulomb (a unit of charge (Q) equal to 6.28 X 10¹⁸ electrons) of charge when a potential of 1 volt is applied across the terminals of the capacitor.
• http://www.tpub.com/neets/book2/3a.htm Have hard copy in Controller / Power Supply binder.

Incremental: [encoder] I believe that the encoder for Gecko must be Incremental, not Absolute.

• Incremental encoders have output signals that repeat over the full range of motion. It is important to understand that each mechanical position is not uniquely defined. When the incremental encoder is turned on, the position of an incremental encoder is not known since the output signals are not unique to any singular position.
• "In steps" An encoder is incremental when the pulses are the same no matter where on the disc or the scale they are produced. There is no way of telling what the angle or position is after a power outage (unless there is some kind of battery back-up). That is why most positions in construction and mining machines are measured with absolute encoders. It would be too time-consuming - sometimes even impossible - to run the machine through a "grid search" routine every time that power has been switched off.

• The long wire is the +.
• Resistor calculator.

• Description of a basic PID controller. http://www.netrino.com/Publications/Glossary/PID.html

Power: (I) [W watt] [HP horsepower] [motor]

• Power [W]= Voltage [V] * Current [A]
• Watts = Volts * Amps
• Watts = Horsepower * 746
• 1HP = 735 W (or about 746 if using SI horsepower or imperial horsepower)

= (Rated (continuous) speed (RPM) * Rated (continuous) torque (in-oz)) / 1351

Resistance: [Ω]

Screw Efficiency: (η)

• Ball screw (η) = 0.9
• A screw/nut drive system utilizing a series of bearing balls between the screw and nut to improve the screws mechanical efficiency and wear life. Ball screws are 80% - 90% efficient. See the Ball Screws section for more information.
• ACME/trapezoidal screw (η) = 0.3 - 0.4
• A screw thread series first developed in 1895 to replace square threads for use in positioning and power transmission. Acme screws are the most widely used power screws, popular in all industries for linear motion. See the Acme section for more information.
• Thread (η) = 0.1 - 0.2

• This is the faster speed.
• This is the maximum speed that the motor can take. The POWER is more or less constant from Normal Speed to Full Speed.

• This is a slower speed than Peak.
• A servomotor has an almost constant TORQUE up to the Normal Speed. This is the highest speed at which the motor's full torque can be utilized.
• This is the appropriate speed of the motor at rated output. From the standpoint of utility, it is the most desirable speed.
• Example from Mariss Freimanis's posting on CNCzone: RPM at rated load = (1 - T_Peak / T_Rated) * no-load RPM = 0.8 * 4345 = 3476 RPM

Torque - (T)

From Mariss on CNCzone;- "This is the torque the motor will deliver if its shaft is prevented from turning. This is a more impressive number so manufacturers and vendors tout it. Typically Peak torque is 5 to 10 times greater than Continuous torque. Current is directly proportional to torque so peak current is 5 to 10 times the continuous rating. Motor heating goes up with the square of the current, being primarily 'I-squared-R'. This means the motor will develop between 25 times to 100 times more heat than it can safely dissipate while delivering peak stall torque. Not a good thing; keep your load at or below the max continuous torque limit."

T_Stall = 5* T_Cont : From Mariss Freimanis's posting on CNCzone The 5 is a guess on his part because the peak (stall) torque was not provided.

The maximum torque a brushless motor can deliver for short periods of time. Operating PacTorq motors above the maximum torque value can cause demagnetization of the rare-earth magnets. This is an irreversible effect that will alter the motor characteristics and degrade performance. This is also known as peak current.

The allowable peak torque applied to the output shaft when normally started from a stop or normally stopped from a running mode.

• In Moog datasheet. This value is slightly above the Rated Torque.

• From Mariss on CNCzone;- "Maximum Continuous Stall Torque: This is actually the maximum continuous torque rating for a motor. The emphasis is on 'continuous' as in 'do not exceed except for short periods of time'. You do, you burn your motor down."
• The stall current is conservatively 6 times the Continuous Rated Torque.
• The amount of torque at zero speed, which a motor can continuously deliver without exceeding its thermal rating. Determined by applying DC current through two windings with rotor locked, while monitoring temperature. Specified with motor windings at maximum rated temperature, with motor in 25 degrees C ambient, mounted to a heat sink. Refer to individual specs for heat sink size.
• This is the torque created when the motor is continuously producing rated output at rated voltage and frequency. It is the torque at rated speed.
• The maximum allowable continuous torque a motor can handle without exceeding the motor temperature limits,

• In Moog datasheet.

Torque Constant (K_T = lb-ft./A) [motor]

• Potential difference (volt, V) = Current (ampere, A) * Resistance (ohm, Ω)
• Unit of measure for electromotive force (EMF), the electrical potential between two points. An electrical potential of 1 volt will push 1 ampere of current through a 1-ohm resistive load.
• Gecko says ~ Do not use a power supply voltage more than 5 volts in excess of the motor's rated voltage.

• In Moog datasheet. This is a range , for example 12 - 60 VDC.

• In Moog datasheet. This is a fixed value, for example 36 VDC.

Voltage Constant (K_E) (V/kRPM peak, line-to-line) [motor] [motor]

Mage.

| K_V = K_T / 1.351 From Mariss F

Kt * 13.662 = Ke

Ke = Kt * 13.662

Ke = Kt / 0.8538

Ke = Kt * 11.834

Ke = Kt * 189.34

Ke = Kt / 0.8538

Boltzmann's constant

 Volts Root Mean Squared: (VRMS)

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