Baby MIND Collaboration Meeting #2 LED Driver Georgi Mitev 18.11.2016

Initial LED driver design and use Single channel design 16 amplitude levels 50ns min pulse width Onboard LED, modified to work with external LED RS-232 interface Manual control and mode display MCU LED driver amplitude timing 1

Pulse Shape 2 200 ns pulse 50 ns pulse 200 ns pulse, fed to LEDs over 2m coax 50 ns pulse, fed to LEDs over 2m coax 2

Master timing control unit Upgraded LED driver Oscilloscope Optical Pulse Control unit Optical pulse feedback Timing pulse channel 1, 2 & 3 LED tube & fiber bundle coupling 3- channel amplitude control unit Optical fiber bundle . . . . . Amplitude control bus I2C Onboard USB & WiFi to RS-232 bridges Master timing control unit 3

LED driver modules block diagrams 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   Round board - interface and signal distribution PULSE From the Main unit I2C Addr. Sel. I2C - PIO Level translator DAC1 DAC2 DAC3 LED Driver 1 LED Driver 2 LED Driver 3 Current mirror Current mirror Current mirror LED1 LED2 LED1 BLUE GREEN RED Rectangular boards – LED driver I2C Pulse I2C Pulse I2C Pulse System controller block diagram LED tube unit block diagram 4

Light output measurements with PIN diode Some signal is observed on the PIN diode (green trace 4), but it’s hard to observe any signal parameters due to the noise. It can be seen that the light emission starts and stops immediately with the current flowing through the LED. It was determined that the aluminium foil, used to wrap the LED & PIN setup, is acting as a wave guide and is channeling the electrical noise from the LED to the PIN diode. Trace 1 – 30ns timing pulse Trace 2 – LED current Trace 3 – LED voltage Trace 4 – PIN diode output 5

Light output measurements with SiPM Measured output increases to between 10 and 50 p.e. Timing pulse width = 15.8 ns, maximum amplitude 6

Current state of the new LED driver P W A Pulse Output 1 Pulse Output 2 Separately controlled T – period (65.5μs)* P – phase/delay* W – width(8ns)* A – amplitude (32 levels) *in 1ns steps Hardware – 4 sets Controller LED torch boards assembly x2 SMA timing cables x2 USB A – USB B cables x3 LED torch tube & fiber bundle x2 Firmware Basic pulse parameters control Advanced pulse control (pulse packets, longer period) Onboard measurement circuit Communication protocol Control Interface Terminal program GUI program Development status - complete - incomplete - not started 7

Bar tests The LED driver is used to test the bar WLS fiber. All bars currently in the dark room have been tested. 8

Bar tests Due to lack of optical fiber bundles for the new LED system an alternative setup is used for testing. One of the new LED drivers is modified to output the pulse on an SMA connector. A short cable is used to connect it to the old fiber bundle. Current test experience – it takes 20-30 min. to test 32 horizontal bars. Most of the time goes into handling the bars. 9

Half module tests Module assembly, module testing and bar testing can go in parallel. Once a half module is assembled it can be tested quickly with the LED system. The possible test setups are being evaluated. 10

Conclusions The new LED system has been developed and tested. Four sets have been delivered to Geneva. It has been used to test the currently available scintillating bars. A GUI application is under development. 11