Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

October 13, 2025, 09:08:06 AM

Login with username, password and session length

Recent Posts

 

3D-printed enclosure for a home-made LDR/LED combination

Started by aquataur, October 11, 2025, 09:41:11 AM

Previous topic - Next topic

aquataur

After being inspired by @Phatt's notes, I looked into Mictester's RCC compressor. In earlier days I would have mounted the LDR/LED combination the way it is frequently suggested, namely by a heat shrinking tube. This has drawbacks which I will address further down.
3D-printers are becoming increasingly common, and since I have access to such a very versatile thing, I quickly made up a small case that does it.

I had some gray filament on the spool, and you would think a 1mm thick non opaque plastic would be light-tight, but no. To my surprise it was translucent enough to be registered by the LDR.
So the filament HAS to be pitch-black. You can test the result by shining your workplace light on it – there must be no reaction by the LDR.

I used a common 8-20k, 1M (dark) LDR and two square LEDs that were left over from a VU-display. I believe they are all very similar in shape, but otherwise you can take the idea and adapt the case.

Note that in my routing program the lid is not shown. You see it in the 3d view. Neither are the LEDs nor the LDR. You see the finished assembly on the fotos, before closing of course. The footprint has grid lines for you to extract the measures (25 mil).

I found that the epoxy PCB, although being opaque, transports enough stray light which shines through the inevitable mounting holes to irritate the sensor.

The flanges on the ,,coffin" are solely there to provide more shading. I also made polygon areas (that are not connected to anything) around the pins for the same reason. For the prototype, I took a permanent marker and covered the area around the pins in black on both layers.
(Note the photo shows the prototype that does not yet have those improvements).
This stops all unwanted light intrusion.

Alternatively, after soldering, one could fill the mounting holes from the top with ahem, something, which unfortunately I failed to imagine. It would need to be black I guess. JBWeld? Suggestions are welcome.

Before you close the lid and glue it (be careful with super glue – it tends to produce deposit on nearby surfaces, I used fast curing epoxy), power up the unit and make sure both LEDs light up. Don´t expect to see a blinding light, you only see a tiny spark.

So back to why heat-shrink tubes are problematic:

    • during heat shrinking the components might shift place
    • the butt ends must be light-tight
    • the whole contraption can become pretty clumsy.

The depicted principle can be adapted to any LDR/LED combination.
The RCC now produces a subjectively very deep compression (too deep to be useful in the extreme setting).

Unfortunately, I cannot upload the STLs here. Find them on my server.

J M Fahey

Hey, cool!!!!

You modern kids with your newfangled stuff often awe us oldtimers  :tu:

Me?

I would have made that case out of wood, held together with some hot hide glue, kept warm in a water bath over my wood fired stove.
Already used to the stink.  :lmao:

Serious, LDRs are very sensitive to the minutest speck of light reaching them, even if invisible to the naked eye.

aquataur

Quote from: J M Fahey on October 11, 2025, 05:10:43 PMYou modern kids with your newfangled stuff often awe us oldtimers

Haha, "kids", haha thank you for the flattery. You would be surprised. I just retired from my work.
But it is true that the "kids" there (who are in their mid-thirties too) impressed me with that "new fangled" technology. I saw that it fills a gap that existed between wood logs, iron rods, sheet metal, acrylic sheets and concrete. As you say.

They were holding a free internal course on 3d design in my working place and I jumped in. There are a million applications waiting in a creative mind's basement that can finally be realized very elegant and efficient.

A small case like for the Vactrol is conjured up in half an hour.

J M Fahey

Cool!!! :dbtu:

I didn´t fall (yet) inside that frying pan but never say never  :cheesy:

Possibilities are truly immense, specially for complex parts which can NOT be pulled from sheet metal/plastic  or rods or tubes or similar without heavy machining.

Old Tech wa to do some basic shape and cut parts out of those.

3D printing just prints complex parts out of the blue.

Was thinking, for example, of knobs or similar.

aquataur

Not to bust the subject of this thread, but a warning ahead. 3D printing is a can of worms. As with everything, I advise to look into this subject only if you are determined to spend a lot of time with the subject. Don't be betrayed by the simplicity of a printed thing. An immense amount of work and knowledge goes into some designs, so that the print comes out smooth, functional and appealing.

Go to somebody who is in the know armed with a ready made .STL file such as the one I uploaded, buy the guy a coffee and wait for the print to complete. That's the way to go.

Look at the knobs a guy makes who does professional printing for the matter. Knobs are not only a functional element, but also your haptic and visual interface to a device. That said, his knobs are meant to go to cooking places and thus are just functional. Better a not-so-perfect knob than none.
3D printing has advanced incredibly in a short time, but for strength and surface cosmetics, a conventionally manufactured knob is unsurpassed.

A functional thing as the housing for a vactrol has no claim for a perfect look neither for durability.