Hi all, I’m wanting to have a cool white led ring or strip powered from a raspberry pi 3b+ running octoprint and a picamera. The LEDs don’t need to be controllable, that’s a bonus that can be done with a plugin using GPIO.
Problem is all I can find are either 5v 1A LED rings, which is way too much current, or tiny RGB LED rings that I don’t want to program.
I also can’t find just a ring PCB to attach cool white LEDs to, that would be simple to do as well.
At this stage, the best options appears to be to get an RGB LED ring, remove the RGB LEDs and just connect white ones and then make a cable to connect to the 5V & ground pins.
Can anyone help with some really basic suggestions or examples?
If you want a ring with several LEDs you are going to need power (Volts AND Current) to drive them. There is no magic way around that. If the Pi 3b does not have the current capability then so be it.
I think the Pi is a microprocessor not a power source. You would normally use it to control “something else” and the “something else” supplies the required power.
Cheers Bob
which sort of implies several not a couple.
And I believe the Pi would quote a maximum current capability and if you need more you have to find something else or another way of achieving your required result.
Cheers Bob
Hi Bridget
Add on. This is the sort of thing to do. How to use a separate supply (suggestion).
Cheers Bob
There should be a junction blob where the ground wire meets the ground symbol.
As for what we’ve got, most of our rings are controllable but there is one that isn’t:
You could definitely use that one with a small regulator and a MOSFET to drive it from GPIO and power it from your printer supply
There’s also non-addressable strips that draw 6W for 50cm, and can be trimmed into 5cm bits, so you could cut down on the power draw that way,
For what it’s worth, my printer enclosure is illuminated by about 40W of LEDs and I have to turn them down quite a bit to stop them from burning my eyes out
Let us know what you think of the above, and we might be able to home in on the right parts
-James
Could I remove those LEDs and put on cool white ones and then just hook it up to 5V and ground on the pi?
I am not sure how to integrate coding with octoprint in a way that wouldn’t be too cumbersome. I’m at a very basic coding level now, can just get some motors and servos to do a few things on a pi with hats set up to just mess around with. I don’t want to mess up my octoprint setups.
You are not going to gain anything by doing that. You are still going to have to power the same number of LEDs and for any more than a couple of “standard” 3 or 5mm LEDs you are going to have to power them separately. I don’t know what the max current available from each GPIO pin on a Pi is but it won’t be more than a few tens of milliamps.
If ou use the circuit I posted above and this ring light
with a 9V supply you should be OK I think. Reading the description of that light it reads as if the current limiting is built in and is designed to connect straight to the 9V supply. Someone from Core might confirm that. Unfortunately, (as is getting more common these days) the technical details are pretty useless. It would be nice to have some idea of the current requirement (without having to measure it) so one could have an idea of what sort of power supply is required. Core please take note!!!
Cheers Bob
I really don’t want to be adding additional power sources and stuff for a couple of LEDs though. Surely a pi with a camera and nothing else can spare enough current from its 5V pins whilst using an official pi power supply?
I already have printers, pis, filament dryers all with their own power supplies and everything in this one little area. I just want some simple illumination so that I can see the camera feed in my browser, it shouldn’t need extra power and circuits surely?
I think you probably do. Unless one of your existing supplies has some spare capacity and you can tap into that. You need to be sure though.
I don’t think you quite understand. A ring light will have much more than a “couple” of LEDs. Bright LEDs can be a bit hungry when it comes to current. Those NEO Pixels as in the addressable strip lights actually have 3 LEDs in them and when producing white light at full brightness use about 20mA each (total 60mA for each Pixel) so if your GPIO pin is only good for say 40mA it would not even drive one of these LEDs. For instance one of those strips with 140 Pixels at full white would require about 8.5A to drive it.
The GPIO pins are designed to drive very light loads up to about 20mA on average or logic devices where the load is a fraction of a mA. For instance the Max input current that can drive the Mosfet in that circuit is 5mA (due to the 1k series Gate resistor) and the current when the Mosfet is charged would be measured in µA or even Pico A. ie; very minute, yet the Mosfet itself would have very little trouble switching 10 or 15A. One reason why they are so useful as switches.
Unfortunately you can’t pull power out of thin air, you have to provide it.
Cheers Bob
The pi power supply says it is 2.5A a 3B+ and pi camera should be using between 0.5 to 1A from what I can gather, so there should be a spare 1A for LEDs hooked directly up to the 5V pin.
It is just weird that I can’t find a simple product to do the job.
You can possibly take the power supply from the Pi Power supply, but you are not going to be able to pull enough power from the GPIO data pins, but if I read correctly you dont want to do that anyway.
It depends on the draw of the LEDs that you have, but if you power them directly off the 5v pins on GPIO you might get away with it.
The issue that you might have is that by using the 5v and GND from the GPIO you are on the wrong side of the power supply, so that is Pi 5v, not power supply 5v.
To really put the issue to bed, you could split the power before it gets to the pi and run the lights directly from that.
Taking a deeper look, would something like this work?
(I’d usually link the product but our site is down for maintenance for a short period at the moment) Back!
It can run on 3 AAs, so it shouldn’t draw more than 1A.
Keep an eye out for undervoltage warnings if you do try to piggyback off the Pi’s supply.
Since this is attached to a printer with a (presumably) beefy 24V supply, a regulator like the one I mentioned earlier would bypass any Pi related power issues.
-James
P.S regarding:
The technical details are pretty useless. It would be nice to have some idea of the current requirement (without having to measure it) so one could have an idea of what sort of power supply is required. Core please take note! !!
Good point @Robert93820! I’ll get some current measurements on a benchtop supply this afternoon if I get time!
The number of LEDs shouldn't be too much of an issue power-wise (you can turn off every second LED to get the same 360-degree lighting effect - a WS2812's quiescent current will be about 1mA).
In terms of powering the lights, you should be able to pull atleast 15 LED’s(at a reasonable brightness ~20mA each) worth of current out of the Pi’s 5V pin (note the documenation the 3B+'s stress test current draw will be a close approximation).
For anyone in the future looking to hook up some addressable LEDs with OctoPrint you can use a plugin like this one to control them: WS281x LED Status
Also worth noting the Neopixel(WS2812b) Uberguide - Make sure to connect that 330 ohm resistor in series with the data in pin!
PS: the Raspberry Pi Pico also makes for a simple dedicated driver for WS2812’s (perfect if you only need one colour as well, for time-lapses make sure to keep ‘redrawing’ the colours every minute or so, if anyone is interested in the code let me know!
Theoretically you could, but it’d probably be more trouble than it’s worth. Honestly a cheap usb selfie ring and a usb power splitter would be easier, or just plug into one of the usb ports on the pi, if you’ve got one free.
Hahah I just came back here to say the same thing.
I just had the realisation that you should be able to find something that is USB powered and just plug it in to the Pi.
You should not have to do that. You should be able to lean on the suppliers to at least supply some basic information. There are quite a few of your suppliers who fall into the little or no useful information category. Sometimes one has to struggle even after visiting the authoring suppliers web site. Basic info should be a prerequisite to being allowed to market a product.
Cheers Bob
