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I want to use an old webcam module from a notebook which needs 3.3V. Therefore I want to solder it to a USB cable and use it at an USB port on my computer. For now I use the 3.3V source from a raspberry, which works fine, but of course that's not very convenient. Most tutorials on the web on how to reuse an old webcam don't use a voltage regulator at all and it seems to work well for them for some reason. But I don't want to damage my computer, so I want to do it properly.

These are all the methods I found other people using to use the USB 5V for their 3.3V webcam:

Element Source
2 x 1N1004 Diodes instructables @AikonM
LM1117 instructables @misterxp
IN4001 Diode instructables @danjunk-DIY
LE33 instructables @DiegoF42
LM1117T & 2 x 10uf tantalum capacitors thingsconnected.io

Without the context of using a webcam I also found people using the AMS1117-3.3 see this users answer which seems to me the "safest" method so far to me. Somewhere I also read a bout using buck converter for that. Finally I read in this post that I probably should use a LDO switching regulator.

Now I am very confused and really don't know what to use. On the one side I definitely want to be on the safe side to not destroy my computer (and maybe the webcam itself ;) ) and on the other side I don't want to pay more for the converter than the webcam is worth. From what I understood simply using diodes is not safe, because both the voltage and the current are not guaranteed to be constant, since the USB specification allows a voltage between 4.3-5V. With that on my mind LM1117 or AMS1117 seem to be the better choice, but also I couldn't figure out what the difference in these two is.

Can someone explain what and also why to use it for this use case?

Sources:
  1. Connecting old webcam via USB
  2. Reusing Webcam and Monitor from old laptop
  3. https://www.youtube.com/watch?v=8dQfgDdJSmk
  4. https://www.youtube.com/watch?v=g8XbDJLKKys
  5. https://hackaday.io/project/110436-laptop-webcam-reuse-made-simple
  6. https://www.instructables.com/Reuse-old-laptop-webcam/
  7. https://www.instructables.com/Laptoprecycling-Webcam/
  8. https://www.raspberrypi.org/forums/viewtopic.php?t=140849
  9. https://buger.dread.cz/how-to-reuse-webcam-module-from-dead-notebook.html
  10. https://www.thingsconnected.io/complete-guide-reuse-laptop-webcam/

brhans
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Night Train
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  • How much current does the camera draw? – Mattman944 Mar 20 '21 at 13:43
  • I didn't know how to measure it, and I couldn't find the specifications. But I know until USB 2 it is between 100mA and 500mA USB 3.0 already goes up to 900mA. https://en.wikipedia.org/wiki/USB#Power – Night Train Mar 20 '21 at 14:12
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    To get more than 100 mA, the device must negotiate for more current. Your situation won't allow this, you are limited to 100 mA. – Mattman944 Mar 20 '21 at 14:19
  • How do you know the module needs 3.3V? If it already connects to USB, albeit internally in the laptop, it could still have 5V like standard USB. – Justme Mar 20 '21 at 14:20
  • In one of the tutorials someone suggested to first try to use the webcam module with a 3.3V source. If that works it is a webcam module that uses 3.3V instead of 5V. Apparently all internal notebook webcam modules use either 3.3V or 5V. – Night Train Mar 20 '21 at 14:24
  • @Mattman944 then my webacm module uses 100mA for sure? Since the minimum output of USB is 100mA, right? – Night Train Mar 20 '21 at 14:25
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    Embedded webcams are usually USB2 devices. As such, they are designed not to consume more than 500 mA. Therefore ANY voltage regulator with capability of 500 mA and above will do the job with 110% likehood.. Bigger regulators (as 1117-types in SOT-223 and bigger cases) will let you use them without heat sink. – Ale..chenski Mar 21 '21 at 21:56

2 Answers2

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Simply, you need a step down voltage converter.

One common one is called LDO, those are device are dropping the voltage at a set value by dissipation. The advantage is that they are small, you only need a single component and they are cheap. However, the conversion efficiency is low as the energy is wasted.

Another are called step down buck converter. Those are usually more expensive, takes more space but are more efficient. They also produce more switching noise.

There are plenty of other types but For your purpose, the step down buck converter is the way to go. You can check on digikey for dc/DC buck converter modules. There are thousands of them. Just make sure to select one that can output the current you need.

Damien
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  • Thanks! I also just found this link https://forum.arduino.cc/index.php?topic=393028.0 where someone asked for the differnce of LM1117, AMS1117 and Buck converter. From what I understood the buck converter is the same as a step-down converter, right? – Night Train Mar 20 '21 at 14:28
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    all three are step-down converters. LM1117 and AMS1117 are two model numbers of linear regulators, specifically of low-dropout regulators (LDOs), and "buck" is an architecture for switch-mode step-down converter, not a manufacturer model number. – Marcus Müller Mar 20 '21 at 15:17
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    A buck converter is a type of step-down converter, like a truck is a type of vehicle. @NightTrain – Damien Mar 22 '21 at 04:11
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If a guy has a desktop power supply laying around, he can use the 3.3 volt rail, but it would be a little bulky if you needed to be free from your bench. The way to go is to have a 3.3 volt regulator, which can be small enouph to hide in the cable to make it look "pretty".

Dr. Dorfus Dingle
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