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NUBM31 Drivers
Thought this might be a worthwhile post as I've encountered a little difficulty when using these drivers with a TTL input. Their standard configuration is active low which can be dangerous for unsuspecting users, switching on the laser without any input. The current control is also a little finicky as it adjusts over a narrow band given the range of the potentiometer. Given that most newer control boards also have 3.3V outputs and this driver requires a 5V input, a little bit of reworking is required to get these drivers to suit our intentions. There will be many ways to achieve the following but I will share with you how I managed to do so.

To achieve active high trigger control, create a level shift to suit 3.3V, and impose a maximum current/power level we can utilize the soft start pin (pin 8.) on the SC3525A PWM chip. This provides us with a direct interface to the internal current limiting features of this chip. Illustrated below:

[Image: Untitled.png]

Pulling this pin low effectively shuts down the unit. I've found applying the output of a voltage divider on C_soft-start will allow you to level shift to 3.3V and broaden the effective number of bits. Here is an example of what I am referring to:

[Image: Untitled.png]

The capacitor is simply there to ensure the system is held low during startup and during switching, acting a noise suppressant. You can connect a PWM signal to the input of R1 providing you have a reference to ground between your control board and the driver. With this configuration I have managed to achieve an active range of 175 (80 - 255 / 12W - 95W) as opposed to the default TTL input which only yielded 50 points of resolution (100 - 150 / 12W to 95W)

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