I have a heating controller hidden in a cupboard which is itself hidden at the back of a cupboard filled with file boxes... it is a pain to remove dozens of file boxes and a couple of shelves just to be able to see the controller LEDs.

Maybe a webcam is a solution, but there are some constraints:

  1. I have only 12 cm between the inside surface of inner cupboard door and the front of the control panel. Somehow the camera thickness lens-to-back plus its minimum (almost) focussed distance has to fit in 12 cm.

  2. The inner cupboard is in total darkness apart from the LEDs I'm trying to monitor.


Mac compatible

90° viewing angle (could survive with around 70° but this omits the non-critical "pump on" LED.


So cool if the cam could connect to my WiFi, but USB power & data will do.


Blurred image due to imperfect close-focus: I only need to differentiate between On / Off / 2Hz flashing LED and between Red or Yellow on each of the six critical LEDs

Hi-Res: I only need enough definition to determine which LEDs are doing what.

Frame rate: I only need to see the 2 Hz flash -- 4 fps should do that.


I have no issue to drill through the 1.3cm inner door if there is some alternative device (a video door peep-hole for example). I have any amount of space OUTSIDE the inner-cupboard door.

So there you have it: thin webcam with close focus ability on high-contrast scene (bright LED in total darkness).

Suggestions?? Thanks Chris

  • As cool as the webcam solution is, it seems like it'd be a lot more elegant just to wire the LEDs to come through the cabinet. Is there something impeding that? Alternatively, what about installing optics and mounting the camera outside?
    – JMY1000
    Commented Jan 7, 2018 at 21:36
  • @JMY1000, This is a closed-box Honeywell underfloor heating controller -- me rewiring the LEDs is, at least, hugely invasive and has possibly expensive consequences (thermal & financial) if my intervention goes banana shaped. I understand your elegance-think (I already tried light pipes), but I prefer to see the beast "as is" on camera. Commented Jan 7, 2018 at 21:52
  • I see. Yeah, besides that, the only thing I can think of is fibre optics, but a camera seems to be a reasonable solution. That or individual light sensors taped down to the controller.
    – JMY1000
    Commented Jan 7, 2018 at 22:03
  • Light pipes are a cool idea, too bad it doesn't work for you. A light pipe can be as simple as an acrylic rod with good optical contact on the source and a polished end at the destination, or even a frosted one.
    – fred_dot_u
    Commented Jan 7, 2018 at 22:16

2 Answers 2


If you haven't rejected the option of using a Raspberry Pi with pi-cam as a system, you'd be getting all of your required features, plus remote access, as the pi could be configured to display the images when polled by a web browser. I'm using Octoprint on my 3D printer, but use an ordinary web cam attached to the Pi. I am able to view images via web browser from the web cam, and I know that a pi-cam would provide the same capability.

A quick check on the pi-cam shows that good focus has been accomplished as low as 30 mm with the V2 NoIR camera module. There are many specifications for both versions of cameras here: Raspberry Pi Camera Specifications

There are tons of resources (kilograms?) for configuring a Pi with an operating system of choice, and almost as many for configuring the camera and accessory software. It's clearly not possible to list them all buy I've picked a couple in the links to show some appropriate representative resources.

  • Whoooo - investigating tomorrow (23:07 here and perhaps a glass of wine or two has passed my lips -- doesn't aid smart thinking). 30mm focus sounds magical, view angle I will discover tomorrow. Many thanks fred.u Commented Jan 7, 2018 at 22:10

The simple solution was to go out and buy a cheap webcam (cheaper than PiCam without the Pi): the image is severely unfocussed but perfectly good enough to know the status of each LED (but not wide-angle enough to capture the non-critical "pump on" LED). The image is also mirror-image (took me a while to work out why), but I guess that will sort itself out if I video-chat to my mac from another machine.

As a newbie to Pi there is no way I could implement PiCam within the time my wife will accept all the file boxes strewn around the place, but it is a fascinating project that I will pursue. I've known about Pi since its early days but never bumbled into a use for it until now. Thanks fred_dot_u for the suggestion.

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