Motor winding insulation temperature ratings
NEMA classes are A (105C), B (130C), F (155C), H (180C). Class B is the most prevalent since 1960's.
SLA Battery Charging
Current limited (0.25C) charge to 2.45V/cell then drop to 2.30V/cell.
LiFePO4 Battery Charging
Current limited (0.2C - 0.7C) charge to 3.65V/cell hold till the current drops to 10% of initial charge rate.
Chip Resistors
0402 resistors are most commonly 1/16W.
0603 resistors are most commonly 1/10W.
0805 resistors are most commonly 1/8W.
1206 resistors are most commonly 1/4W.
Tantalum Capacitors
The voltage ratings are usually 50V or below. Even at 50V, the large value tantalum capacitors are expensive, so Aluminum electrolytic should be considered instead.
Relay
1-Form-A: single pole normally open
1-Form-B: single pole normally closed
1-Form-C: single pole double throw
Monday, March 26, 2012
Sunday, March 4, 2012
EEssential Weekly Notes #5
Ferrite bead vs Inductor
The ferrite bead is lossy at high frequencies, i.e. low Q or resistive. The high frequency energy are absorbed and dissipated as heat. A pure inductor is non-lossy and stores energy. While a real inductor has some inevitable resistive element, it absorbs energy equally at all frequencies.
Mu-Metal
Mu-metal is high permeability material; it achieves the magnetic field shielding by redirecting magnetic field lines.
The ferrite bead is lossy at high frequencies, i.e. low Q or resistive. The high frequency energy are absorbed and dissipated as heat. A pure inductor is non-lossy and stores energy. While a real inductor has some inevitable resistive element, it absorbs energy equally at all frequencies.
Mu-Metal
Mu-metal is high permeability material; it achieves the magnetic field shielding by redirecting magnetic field lines.
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