To control the laser diodes, we imposed a set of constraints:
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Computer control of the laser power using a PWM signal (Mojo FPGA or Arduino).
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Triggering of the laser diodes (μs range) using a TTL signal.
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Capping of the current supplied to the laser diodes to avoid damages.
We present here two systems to drive the diodes: the electronics used in the manuscript and an alternative solution. Both are based on custom boards and commercial laser diode driver.
Note that different laser diodes have different voltage and current requirements, which complicates the task of finding a unique solution for all diodes of the laser engine:
| From the datasheets | 405 nm, 80 mW (dl-7146-301s, Sanyo) |
488 nm, 55 mW (BLD-488-55, lasertack) |
640 nm, 700 mW (HL63193MG, Oclaro) |
|---|---|---|---|
| Threshold current | 60 mA | 60 mA | 250 mA |
| Max operating current | 140 mA | 135 mA | 1000 mA |
| Max operating voltage | 6 V | 7.5 V | 2.6 V |
We explored two solutions to control the laser diodes (we highlighted in bold each feature that is more advantageous in one version than in the other):
| Electronics (manuscript) | Electronics (alternative) | |
|---|---|---|
| Status | Daily use on our microscopes | Tested with a prototype |
| Inputs voltage | 3.3 V (PWM and TTL) | 3.3 V or 5 V (PWM and TTL) |
| LD driver | 4 x EU-38-TTL (total ~80 euros) | 2 x LD3000R + 2 x LD1255R (total >600 euros) |
| Modified LD driver | Yes | No |
| Power supplies | 1 x 5 V (2.5 A) + 1 x 6 V (1 A) | See LD1255R power supply and contact Thorlabs for the LD3000R |
| Power supplies price | ~ 24 euros | prob. ~ 300 euros |
| Custom boards | 4 x signal conditioning + 1 x voltage distribution | 1 x signal conditioning |
| LD pulsing | ~40 μs (640) - 1 ms (488) | few ms |
- Important: The alternative electronics has only been tested with a prototype, while the manuscript version is used daily in our microscopes.
- In both cases, we generated the TTL and PWM signals using a Mojo FPGA. The FPGA firmware was based on the MicroMojo project and interfaced with the computer using Micro-manager. Alternatively, an Arduino can be used (also compatible with Micro-Manager).
- Each custom board was designed in Altium; we uploaded here the Altium projects. Altium projects can be opened with a free license of the Altium Designer Viewer.
- The bill of materials for each custom board was exported in a format compatible with Beta Layout requirements. These can be used with the circuit PCB layout to order an already assembled board.
Both versions were designed by Christian Kieser, Electronics workshop, EMBL.