My Arduino board is Uno.
I want to drive 650nm and 405nm pigtailed laser diodes.
I don’t want to use PWM, so I choose a digital potentiometer MCP4161 10k ohm.
But the current is not high enough to drive laser diodes,
so I searched from the forum and found that I can use a transistor like PN2222 and 2N3904 .
The reference is https://forum.arduino.cc/index.php?topic=192733.0
My schematic is https://flic.kr/p/LhK1Fh
The step of digital potentiometer is 255.
Then the pigtailed laser diode is the brightest.
When I drive 650nm pigtailed laser diode,
current through the base of transistor is 199uA,
current through the collector of transistor is 30mA,
the resistor between digital pot and base is 19k ohm,
the voltage from the regulator is 3.7 volt.
Now the current for the 405nm pigtailed laser diode is over 35mA.
But the current can’t go high anymore.
Batteries are added to 8 volt.
What is the problem of my circuit?
The voltage from the regulator is not enough?
If so, then I can choose different resistor to get a higher voltage out.
The websites are data sheets of
-digital potentiometer MCP4161
The attachments are data sheets of
-650nm and 405nm pigtailed laser diode
My English is not good enough. Sorry about that.
Thanks for helping me solve the problem.
650nm 3mW.pdf (471 KB)
405 3mW.pdf (470 KB)
PN2222A.pdf (279 KB)