Hi there, I am currently working on a project where I need to drive a Laser via PWM. To remove external interference e.g from ambient light, the Laser is driven via PWM at a specific frequency, Everything is working perfectly so far. Unfortunately though, I keep killing laser diodes, I am just us…

[image] mickymik: My drive circuit is only a 2N2222A under the diode, with a 200ohm resistor on the base, and 5v on the emitter. So you have no control over the current then? Just like an LED you can't simply switch the voltage on and off you need something to control the current so that the…

FYI These modules have a series current limiting resistor ~91 ohms. The LED drop on these is ~2.5V, giving 2.5V / 91 ohm = ~ 26mA for 5V applied to the module.

[image] mickymik: My drive circuit is only a 2N2222A under the diode, with a 200ohm resistor on the base, and 5v on the emitter. The PWM is Running at 50% duty cycle. Your description does not describe the connections I would expect. Emitter should be ground and diode should be between the …

[image] mickymik: Unfortunately though, I keep killing laser diodes Check your diodes directly on 5V. If they die then you got a very bad lot and should try a different vendor.

[image] mickymik: My drive circuit is only a 2N2222A under the diode, with a 200ohm resistor on the base, and 5v on the emitter That souds wrong. 0V on the emitter would make sense, the 2222 is an NPN device and should be used as a low-side switch. Laser diodes are very sensitive to drive c…

[image] mickymik: Here is the circuit I can't see any laser nor how it is driven in that circuit.

[image] MarkT: Laser diodes are very sensitive to drive current which needs to be controlled, and they must have heatsinking unless used on a low duty cycle. Those cheap laser diodes only have a current limiting series resistor, more seems not required. An external resistor can be used to dec…

Don't over current laser diodes, the margins are very slim between lasing and frying. A laser diode is basically an LED optimized for very high current densities and with a quantum well (both required to get a population-inversion). The high current densities are why they need both careful current…

Read and digest this link About lasers It is very comprehensive and covers virtually everything you need to know.

[image] Grumpy_Mike: Read and digest this link About lasers Or directly jump to the section applicable to the laser diodes in question.

Cheap laser diodes and PWM

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Grumpy_Mike March 7, 2022, 9:12am 8

I can't see any laser nor how it is driven in that circuit.

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