GRAD Engineering LLC

Color spot light meter ...

Key Benefits

	Measures Red, Green, Blue and White light.
	Measures looks at a small spot and subtract out room light.
	USB and RS232 interface.

Hardware & Firmware by Ron, PCB by Viktor

PERFORMANCE CHARACTERISTICS:

The sensor is capable of measuring light output from a LCD display with white luminance levels in the range of 1,000 cd/m² to 0.1cd/m². The sensor also measures room light.

The sensor resolution is 0.03cd/m².

Accuracy at 500cd/m² is +/- 2%.

Repeatability is +/- 0.1%.

10 readings per second in low resolution mode. (0.3cd/m².)

1 readings per second in high resolution mode. (0.03cd/m².)

Does not need to be synchronized to vertical sync.

Factory calibrated to NIS standards.

MECHINACEL

Clamps to top of monitor. (or any edge)

6 foot USB cable

optional 6 foot Serial cable with optional wall power supply

Measurement arm response time is approximately 0.5 seconds.

ENVIRONMENTAL

The sensor shall comply with in specification for the following ranges, typical with office environments.

Operating Range:

1. Operating temperature 16 to 30 degrees Celsius.

2. Operating humidity range is 20% to 80%, non-condensing.

Storage and transit environmental range:

1. Temperature: -20 to +60 degrees Celsius

2. Humidity: 20% to 80%, con-condensing.

ELECTRICAL INTERFACE

a. USB

USB 1.1/2.0 full speed (12Mb/s)

USB VID, PID, Serial Number and Product Description string

300 byte receive FIFO and 100 byte transmit FIFO, 16millisecond latency

Voltage: 4.5 to 5.5 volts

Current: 450mA max during arm movements. 25mA operating current. Less than 500uA stand by.

Input capacitance less than 10uF. Internally fused at 500mA

USB SOFTWARE DEVELOPMENT information

D2xx (USB Direct Drivers + DLL S/W Interface)

Windows 98, Windows 98 SE

Windows 2000/ME/XP

Virtual COM Port (VCP) Drivers

Windows 98 and Windows 98 SE

Windows 2000 / ME / XP

Windows CE

MAC OS-8 and OS-9

Mac OS-X

Linux 2.40 and up

b. SERIAL (optional)

9600 baud, 8 data bits, no parity bits, 1 stop bit

Tri-state RS232; (for RS232 bus applications) Able to share the PC to Monitor serial port.

Serial port turns on 1mS before data is sent and off 1mS after the end of data.

two character FIFO, no hand shaking

Connector Specifications

8 pin mini-Din

-Pin 3TXD (data from PC)

-Pin 2: RXD (data to PC)

-Pins 5 Gnd

External power (serial only)

Power supply 6 to 10V at 5mA operating. 450mA during arm movement. 500uA stand by.

Center pin 6 to 10 volts

Outside pin is ground

SYSTEM REQUIREMENTS

Windows:

Pentium PC or better

Windows 2000 or XP

128 MB application RAM, 10 MB free disk space.

USB port

COMMAND SET

The command set is based on one character commands.

Responses are in ASCI. Numbers are in ASCI not binary. Responses end in a carriage return

C	The sensor returns an ASCI string that represents the amount of light from the LCD monitor. C=64,000 to C=0 followed by a carriage return (CR). Response time is 1 second. If the sensor arm is not in place an additional 1 second may be added.
c	The sensor returns an ASCI string that represents the amount of light from the LCD monitor. C=64,000 to C=0 followed by a carriage return (CR). Response time is 0.1 second. The resolution is not as good.
?	The sensor returns an ASCI string measuring the amount of light from the LCD monitor. Red, Green, Blue and Clear filters are applied. R=100 G=103 B=102 C=243(CR) Response time is 3 seconds. If the sensor arm is not ready an additional 1 second may be added.
U	Close the arm sensor. The sensor will respond back with (CR) then the arm is retracted. Response time is approximately 0.5 seconds and 0.01 second if the arm is already closed.
D	Open the arm sensor for use. The sensor will respond back with (CR) then the arm is in place. Response time is approximately 0.5 seconds and 0.01 second if the arm is already open.
A	The sensor will return the ambient light. (room light) A=64000(CR) to A=0(CR) Response time is 1 second. If the sensor arm is not ready an additional 1 second may be added.
R	The sensor will return the RED light from the LCD monitor. R=64000(CR) to R=0(CR) Response time is 1 second. If the sensor arm is not ready an additional 1 second may be added.
G	The sensor will return the GREEN light from the LCD monitor. G=64000(CR) to G=0(CR) Response time is 1 second. If the sensor arm is not ready an additional 1 second may be added.
B	The sensor will return the BLUE light from the LCD monitor. B=64000(CR) to B=0(CR) Response time is 1 second. If the sensor arm is not ready an additional 1 second may be added.
W	Wake up command. The response is a carriage return (CR). Used to test the presence of the sensor and to wake up the sensor if it is in low power mode. Response time 0.1 second worst case and often under 0.01 seconds.
	If no command is sent with in 10 seconds the sensor assumes it is not needed. The arm is retracted. Note: An invalid command will reset the 10 second timer and keep the arm active. No response is sent.

In serial (RS232) mode the sensor has a two command buffer. It is ok to send more than one command without waiting for the response. Once the buffer is full all additional commands will be lost!

In USB mode there is a very large buffer. It is possible to send hundreds of commands that will take the sensor two minutes to respond to. It is best to limit the number of commands.