Minolta XK Camera

MINOLTA XK 35MM CAMERA

In 1974 Minolta Camera Corp released, in the USA, a high end professional level 35mm film camera. It was designed to compete with high end cameras from Canon and Nikon. The XK was considered a “SYSTEMS” camera with a complete series of lenses and accessories.

The XK has interchangeable finders and focusing screens. Also, a electronically controlled shutter with speeds of 16 to 1/2000 seconds with the AE finder. The shutter speed can also be infinitely varied between 4 to 1/2000 seconds using a small lever located below the shutter speed dial.

In 2003 Minolta merged with Konica to form Konica Minolta.

Sadly, In January 2006, Konica Minolta announced it would no longer manufacture cameras and other photographic accessories such as film. This ended a nearly 78 year history of camera manufacture.

Eventually, Konica Minolta sold its SLR camera business to Sony.

Link to an excellent resource on Minolta Cameras

 

MINOLTA XK WITH AE FINDER AND 50mm ROKKOR X LENS

 

MINOLTA XK WITH AE FINDER

 

MINOLTA XK WITH AES FINDER AND 50mm ROKKOR X LENS

 

MINOLTA XK WITH AES FINDER

 

MINOLTA XK HIGH MAGNIFICATION FINDER

 

MINOLTA XK 250mm MIRROR LENS

 

 

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MSP430 and DRV8830 Motor Driver

THE MSP430FR2433 LAUNCHPAD AND THE DRV8830

The DRV8830 contains N-channel and P-channel power MOSFET’s configured as an H-bridge and can drive one DC motor or one winding of a stepper motor as well as other loads like solenoids. The output driver can supply up to one amp DC and can operate with supply voltages from 2.75 to 6.8 volts. The internal PWM frequency is 44.5 kHz.

VOLTAGE REGULATION

The DRV8830 uses pulse width modulation (PWM) to maintain a constant motor speed and to compensate for changes in battery supply voltage. The voltage output is programmable via an I2C interface.

The voltage regulation circuit integrates the pulse width modulated output to obtain an average DC voltage value. This filtered PWM output is divided by four and compared to the output of the voltage setting (VSET DAC). If the averaged PWM output is lower than the output voltage setting (VSET DAC), the duty cycle of the PWM output is increased. If the averaged PWM output is higher than the output voltage setting (VSET DAC), the duty cycle of the PWM output is decreased. The voltage setting (VSET DAC) is programmed using the I2C serial interface.

If the programmed output voltage is greater than the supply voltage, the DRV8830 will operate at 100% duty cycle and the voltage regulator operation will be disabled. In this case, the device operates as a conventional “H” bridge.

CURRENT LIMIT

The DRV8830 contains a current sense circuit that uses an external resistor to set the maximum output current to the motor and to protect it in the event of a stalled condition.

The motor current is determined by monitoring the voltage across the external current limit resistor and comparing it to a reference voltage of 200mV. If the current limit voltage exceeds the reference voltage for more than about 3 uS, the PWM duty cycle will be reduced to limit the current to the value set by the sense resistor.

If the overcurrent condition persists, such as in a stalled motor condition, for more than approximately 275 mS, the “FAULTn” pin will be driven low and the “FAULT” and “ILIMIT” bit in the “FAULT” register will be set, and the motor driver will continue to operate.

Setting both bits “IN1” and “IN2” in the “CONTROL” register to either zero (standby/coast) or to one (brake) will clear the fault condition. Setting the “CLEAR” bit in the “FAULT” register or removing supply power to the DRV8830 will also clear the fault condition.

DRV8830 TERMINAL CONNECTIONS
NAMEPINI/ODESCRIPTION
GND5NAGROUND
VCC4NAPOWER SUPPLY
SDA9INPUT/OUTPUTI2C SERIAL DATA
SCL10INPUTI2C SERIAL CLOCK
A07INPUTADDRESS 1
A18INPUTADDRESS 2
FAULTn6OUTPUTFAULT OUTPUT
OUT13OUTPUTMOTOR BRIDGE OUT 1
OUT21OUTPUTMOTOR BRIDGE OUT 2
ISENSE2INPUT/OUTPUTCURRENT SENSE
PORT AND I2C eUSCI CONFIGURATION AND CONTROL

 

 

LINK: Additional Information on the DRV8830

 

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Stepper Motors

The stepper motor is a device used to convert electrical pulses into discrete mechanical rotational movements.

Most common are 2-phase permanent magnet (PM) motors which provide discrete angular movement every time the polarity of a winding is changed.

CONSTRUCTION
In a typical motor, electrical power is applied to two coils. Two stator cups formed around each of these coils, with pole pairs mechanically displaced by 1/2 a pole pitch, become alternately energized North and South magnetic poles. Between the two stator-coil pairs, the displacement is 1/4 of a pole pitch. The permanent magnet rotor is magnetized with the same number of pole pairs as contained by the stator-coil section.

Interaction between the rotor and stator (opposite poles attracting and likes repelling) causes the rotor to move 1/4 of a pole pitch per winding polarity change. A 2-phase motor with 12 pole pairs per stator-coil section would thus move 48 steps per revolution or 7.5° per step.

STEP ANGLE
Step angles for steppers are available in a range from .72° to 90°.
Standard step angles are:

3.6º — 100 steps per revolution.

7.5° — 48 steps per revolution.

15° — 24 steps per revolution.

18° — 20 steps per revolution.

A movement of any multiple of these angles is possible. For example, six steps of a 15° stepper motor would give a movement of 90°.

ACCURACY
A 7.5° stepper motor, either under a load or no load condition, will have a step-to-step accuracy of 6.6% or 0.5º. This error is noncumulative so that even after making a full revolution, the position of the rotor shaft will be 360º ± 0.5º.

The step error is noncumulative. It averages out to zero within a 4-step sequence which corresponds to 360 electrical degrees. A particular step characteristic of the 4-step is to sequence repeatedly using the same coil, magnetic polarity and flux path. Thus, the most accurate movement would be to step in multiples of four, since electrical and magnetic imbalances are eliminated. Increased accuracy also results from movements which are multiples of two steps.

Keeping this in mind, positioning applications should use 2 or 4 steps (or multiples thereof) for each desired measured increment, wherever possible.

BIPOLAR AND UNIPOLAR OPERATION
Stepper motors are available with either 2-coil Bipolar, or 4-coil Unipolar windings. The stator flux with a Bipolar winding is reversed by reversing the current in the winding. It requires a push-pull Bipolar drive.

Care must be taken to design the circuit so that the drive transistors, which are in series, do not short the power supply by coming on at the same time. Properly operated, the Bipolar winding gives the optimum motor performance at low-to-medium step rates.

A Unipolar winding has two coils wound on the same bobbin (one bobbin resides in each stator half) per stator half. Flux is reversed in each coil bobbin assembly by sequentially grounding ends of each half of the coil winding. The use of a Unipolar winding, some times called a bifilar winding, allows the drive circuit to be simplified. Not only are half as many power switches required (4 vs. 8), but the timing is not as critical to prevent a current short through two transistors as is possible with a Bipolar drive.

For a Unipolar motor to have the same number of turns per winding as a Bipolar motor, the wire diameter must be decreased and the resistance increased. As a result, Unipolar motors have 30% less torque at low step rates. However, at higher rates the torque outputs are equivalent.

Information Courtesy: Thomson Industries, Inc.

 

 

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MSP430FR2433 Internal Oscillator

Configure MSP430FR2433 MCLK for 8 Mhz or 16 Mhz internal oscillator.

MSP430FR2433 – 8MHZ INTERNAL OSCILLATOR

MSP430FR2433 – 16MHZ INTERNAL OSCILLATOR

MSP430FR2433 – ROUTE CLOCK TO PORT PINS

 

8 MHZ INTERNAL OSCILLATOR

 

16 MHZ INTERNAL OSCILLATOR

 

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MSP430FR2433 External Oscillator

This code block can be used to add an external clock oscillator to the MSP430FR2433 Launchpad. The code should be located at the top of the MAIN function. Note that it is not necessary to set the direction of P2.0 (xout) and P2.1 (xin) as the input/output direction is automatically set with P2SEL0 and P2SEL1.

An oscilloscope can be used to check clock output on P1.3.

Crystal Oscillator

 

MSP430FR2433 LAUNCHPAD EXTERNAL OSCILLATOR CODE

MSP430FR2433 LAUNCHPAD CLOCK OUTPUT TO PORT PINS CODE

 

MSP430FR2433 LAUNCHPAD WITH EXTERNAL OSCILLATOR

 

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