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I am a complete beginner in this field, so please forgive me if I write something stupid.

I have a power supply that is pretty accurate, and I have been using it to power my projects. However, I need to spin the whole circuit very fast so I need a portable constant current source for my laser diode.

So, I want to create a simple constant power source that is powered by a 9 V battery (or something else) and supplies a constant 30 mA of current. The voltage range I am expecting is 0-3 V.

First, I tried to find a commercially available product, maybe like an LED driver, but guess what. turns out LEDs user a hell lot more power than a IR laser diode, and the ones that did fit in my range didn't ship to my country.

So, I naturally tried to build one myself, and looked all over the internet, and found dozens of tutorials for 1-5 A sources. I even tried to turn them into a more lower current by changing the values of the resistors, but it didn't work.

Can somebody please help me? I'm out of my profession here :(

winny
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Andy_ye
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  • I'm guessing at what the purpose is, but could you use a mirror to direct the light instead of moving the light source? – Andrew Morton Sep 01 '21 at 07:10
  • [More ideas](https://electronics.stackexchange.com/questions/100312/constant-current-source-circuit-improvisation/100315#100315) - [Another idea](https://electronics.stackexchange.com/questions/107699/tl431-constant-current-source/107710#107710) - [Spin-off idea](https://electronics.stackexchange.com/questions/102751/highly-accurate-constant-current-source/102775#102775) - [Howland current pump](https://electronics.stackexchange.com/questions/65753/constant-current-source-math-using-ad8276-differential-op-amp/65774#65774) – Andy aka Sep 01 '21 at 07:11
  • [Even more ideas](https://electronics.stackexchange.com/questions/103787/maintaining-a-constant-current-with-varying-loads/103794#103794) - [Simple op-amp PNP current source](https://electronics.stackexchange.com/questions/350491/constant-current-circuit-with-transistor/350493#350493) – Andy aka Sep 01 '21 at 07:15

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