1. LED driver status update
Georgi M. MITEV
Bulgarian academy of sciences
Baby MIND update meeting #39

2. Initial LED driver design and use
Single channel design
Onboard LED
Adapted to work on external LED
Side effects
RS-232
interface
Manual control and mode display
MCU
LED driver
amplitude
timing
Baby MIND update meeting #39

3. Pulse Shape 200 ns pulse 50 ns pulse
200 ns pulse, fed to LEDs over 2m coax
50 ns pulse, fed to LEDs over 2m coax
Baby MIND update meeting #39

4. LED driver upgrade proposition
Modular system with common pulse timing
Shorter pulse length
Better pulse shape
Multiple wavelengths
Separate diode amplitude control
Oscilloscope
Optical Pulse Control unit
LED tube + optics
3- channel amplitude control unit
Optical fiber bundle
Amplitude control bus I2C
Onboard USB & WiFi to RS-232 bridges
Master timing control unit
timing
Baby MIND update meeting #39

5. LED driver modules block diagram
Two independent time pulse channels
One control pulse channel, connected to either pulse 1 or pulse 2
Up to four I2C unit control channels
Separate amplitude control for each LED
To the remote addressable LED probes
Local control and display
dsPIC33EP64GS504
Wi-Fi module
ESP8266
USB - UART
FT232RL
Real Clock
DS1307
Non-volatile memory FM24VN10
SCI1
SCI2
I2C 2
Control measurement circuit
I2C 1
PULSE1 & PULSE2
control
Chanel 1
Chanel 2
Chanel 3
MS0
MS1
ADC T1
LMH6559 buffer
Power control
MUX
I2C buffer
I2C - PIO
LED Driver 2
LED Driver 3
Addr. Sel.
From the Main unit
Level translator
DAC1
DAC2
DAC3
I2C
PULSE
Current mirror
LED1
LED2
BLUE
GREEN
RED
LED Driver 1
LED unit block diagram
System controller block diagram
Baby MIND update meeting #39

6. Hardware status
A total of 4 system controllers to be produced. One already available in Geneva.
A total of 8 LED units to be produced. One functioning unit available. Still needs some hardware bug fixes. The parts for the fix have already been ordered.
The case for the main units is under development.
The case for the LED units and the optical fiber bundles are yet to be designed and produced.
Baby MIND update meeting #39

7. Software status and preliminary test results
The PWM generator and the amplitude drivers are already developed.
The control logic and communication protocol are under development
Top picture - 8ns pulse fed to the LED unit main board (yellow) and after the LED unit buffer (red)
Bottom picture – 25ns pulse fed to the current mirrors inside the LED unit (yellow) and voltage across the LED (blue)
Baby MIND update meeting #39