What're you up to this weekend?

I want to use multicoloured LEDs as indicators on an instrument front panel and It will need 32 of them. I thought I might use the 2mm square neopixels and I bought 1000 from Aliexpress for about 1.6p (£0.016) each.

I thought I had better see how well they worked.

I'm driving them from the SPI MOSI pin on an ARM processor (Giga Devices GD32E103 and I had to tweak the clock to get a good ratio of high and low times from 4 bits of a 16 bit SPI data word.

Right now the code is using interrupts (one for every 16 bit word transmitted) but I'll change it to use DMA.

Happy to post the code if any one wants to play with it. The GD processor SPI is a pretty much exact clone of earlier ST  ST3210x processors.

I set up a pseudo random thing to drive it (sorry about the kitchen paper optical filter - the camera couldn't cope with bright LEDs).

So I'm pleased to say that the sub 2p neopixels work OK.

Unfortunately the little light pipes (plastic rods a few mm long with a domed end) cost about 5x as much as the pixels - but I need them to get the light through the front panel.

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RE: What're you up to this weekend?

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MK

I've never understood why the light pipes cost so much more than the LEDs themselves! Given that they are approximately the same thing, and one is missing the LED die and leads.

shabaz said:

I've never understood why the light pipes cost so much more than the LEDs themselves!

I'd turn it around. How comes the pixels sell cheaper than the pipes? I think it's based on volume. Pixels are produced in such high volumes, in a competitive market, that it drives the price down.

I asked chatgpt.

"how comes that light pipes for neopixels are more expensive than neopixels themselves?"

In essence, while Neopixels themselves are low-cost due to mass production and simple components, light pipes require specialized materials, precision manufacturing, and are often customized for specific applications, all of which contribute to their higher cost.

There's a longer analysis that I can post if interested.

Typical ChatGPT non-intelligence.

The chip in the neopixel probably uses 40nM geometry, the light guide is a plastic moulding , single homogenous material (acrylic) etc etc.

There's a good video on you tube of a neo pixel factory which shows the parts going through multiple stages of automatic assembly and test.

I suspect that the main issue is that the low volume market for light guides is small. I'm sure they will get pretty cheap if you want enough - but when something cost less than a penny each you need to shift a lot in a day to make a living !

MK

Typical ChatGPT non-intelligence.

The chip in the neopixel probably uses 40nM geometry, the light guide is a plastic moulding , single homogenous material (acrylic) etc etc.

There's a good video on you tube of a neo pixel factory which shows the parts going through multiple stages of automatic assembly and test.

I suspect that the main issue is that the low volume market for light guides is small. I'm sure they will get pretty cheap if you want enough - but when something cost less than a penny each you need to shift a lot in a day to make a living !

MK