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Thread: RGB LED selectable colour

  1. #1

    Default RGB LED selectable colour

    Hi,

    I've joined this forum to ask one question. I've been pulling my hair out trying to find a solution to this for weeks now and Google seemingly has no answers.

    About 10 years ago, Radioshack sold a 7-colour and blinking LED with three pins and after an initial startup cycle every time you touched the ground pin it would display a different colour.
    These are unavailable from Radioshack and it appears that these just do not exist anywhere on the planet any more!
    If anyone knows a supplier for these I'd be very grateful!

    Alternatively as I couldn't find these LEDs I thought I'd look into these RGB LED puck lights that are on eBay, Amazon etc that when you press them they change colour. I opened one up to try and reverse engineer it and inside is a 5050 SMD on a PCB with a switch. On the PCB the only manufacturer numbers are C6D-5050RGB-V1.2 Nothing else to identify it. If anyone knows of a manufacturer or distributer for these PCBs, again I'd be interested.

    I am an exhibit engineer at a science museum and want to create a pixel wall of buttons that when pressed display a different colour. I do not want to go down the Arduino route - I know it's possible but more expensive and also this needs to be a simple and stand-alone as possible. This is the kind of thing I want to produce: https://youtu.be/oLiNdsdbZRE?list=LL

    Thus guy uses arcade buttons and the 7-color and blinking LEDs that Radioshack used to sell... but no more!

    If anyone can help, please give me some ideas!

    Many thanks!

  2. #2
    *Flashaholic* Lynx_Arc's Avatar
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    Default Re: RGB LED selectable colour

    You can buy RGB LED strips with remotes that allow you to choose the color you want using the remote. The remote has 24 buttons on it and has 15 colors you can choose from plus white and has dimming too.
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    Default Re: RGB LED selectable colour

    Try to find a Cree MCE or XM-L RGBW led. Thatís where to start.
    IIRC they are individually addressable leds in a quad die.
    I havenít looked carefully, but there seem to be quite a few reasonably priced
    RGBW controllers available; not that I know what will work for your application.
    Last edited by jabe1; 04-14-2021 at 01:59 PM.
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  4. #4

    Default Re: RGB LED selectable colour

    Thanks but what I am ultimately looking for is an LED (with integrated IC) or a RGB SMD LED on a board that I can change the colour of with the press of a single button.
    The aim is to have multiples of these (100 or 200 in a grid formation) so that you can press them individually and select a colour - creating a wall of coloured pixels.

  5. #5
    Flashaholic* DIWdiver's Avatar
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    Default Re: RGB LED selectable colour

    I looked around, and couldn't see anything like you are looking for. Everything seems to sequence automatically, and not be controlled by the switch. Or have no smarts at all.

    If you had to, you could build your own pretty cheaply. About $1.00 in cost per pixel, including the LED, PCB, and Micro, if you were building hundreds of them. You'd just have to solder wires for the switch and power.

    If you could provide proper mechanical interface, the switch could be mounted right on the PCB for another $0.50 or so. It wouldn't be as rugged as the arcades switches used in the video you linked to, so you'd have to protect it from being crushed.

    This would include a small microprocessor running very simple code. If you can't write it yourself (with some help), you could probably find someone to write it for you. I might even know someone. Spend $10 or so for a programmer, and you're done!

    If you want the whole thing designed, assembled and programmed, the cost would obviously be higher, but there are those who can do that too.

    What's your time frame for getting this done? How many pixels are you thinking about? What's the spacing between them?

  6. #6
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    Default Re: RGB LED selectable colour

    Interesting problem to solve, and I think you've come to the right place!

    Lots of cheap RGB controlled devices around such as strips and low-voltage bulbs, but they are mostly driven through IR remote which does not lend itself to the simple push control you need. I get 3-foot RGB strips with 30 LEDs for $4, but they are all driven to the same colour; no individual control.

    Some RGB LEDs have built-in drivers, designed to be daisy-chained and use serial data from a controller. Again, overkill, higher cost, and selection of these is more limited than plain RGB LEDs.

    Challenge I have found with "reverse engineering" is the control ICs in many of these low-cost devices are difficult/impossible to identify. Using them depends on getting good datasheet, and their availability.

    (1) Some ICs are so small (SOT or SC packages) that a pseudo part number is marked, which may be difficult to trace back to vendor and "real" part number. Sometimes you can luck out, there are some cross-references docs out there. I was very lucky that part marked F113 turned out to be MICRF113 which was found by a quick web search; but more of an exception.

    (2) Some ICs have either no markings, or they are removed ("sanded off"?) to hinder copying the design.

    (3) Some products use COB (Chip On Board) with die directly mounted and bonded to PCB, covered by blob of epoxy, usually no markings. You probably could not get the chip in packaged form anyway.

    AS DIW alluded to, small microcontroller, even an 8-pin PIC for 50c each, could do simple sequencing. Code would be fairly simple. This assumes you'd do the design work, if nothing OTS shows up.

    Simple 7-colour sequence consists of R,G,B,RG,RB,BG,and RBG in some order. Is this what you're looking for? Also, is an "off" state part of sequence?

    If you want to build control circuit, a simple 3-bit binary counter could provide this 7-colour sequence, at low cost, with commonly available chips. You'd need a few driver transistors, no big deal.

    Dave
    Last edited by Dave_H; 04-15-2021 at 07:26 AM.

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    Default Re: RGB LED selectable colour

    Quote Originally Posted by mrmop View Post
    Hi,

    I've joined this forum to ask one question. I've been pulling my hair out trying to find a solution to this for weeks now and Google seemingly has no answers.

    About 10 years ago, Radioshack sold a 7-colour and blinking LED with three pins and after an initial startup cycle every time you touched the ground pin it would display a different colour.
    These are unavailable from Radioshack and it appears that these just do not exist anywhere on the planet any more!
    If anyone knows a supplier for these I'd be very grateful!

    Alternatively as I couldn't find these LEDs I thought I'd look into these RGB LED puck lights that are on eBay, Amazon etc that when you press them they change colour. I opened one up to try and reverse engineer it and inside is a 5050 SMD on a PCB with a switch. On the PCB the only manufacturer numbers are C6D-5050RGB-V1.2 Nothing else to identify it. If anyone knows of a manufacturer or distributer for these PCBs, again I'd be interested.

    I am an exhibit engineer at a science museum and want to create a pixel wall of buttons that when pressed display a different colour. I do not want to go down the Arduino route - I know it's possible but more expensive and also this needs to be a simple and stand-alone as possible. This is the kind of thing I want to produce: https://youtu.be/oLiNdsdbZRE?list=LL

    Thus guy uses arcade buttons and the 7-color and blinking LEDs that Radioshack used to sell... but no more!

    If anyone can help, please give me some ideas!

    Many thanks!

    Hi. Cool idea. And I understand the goal, each pixel an LED and a spring and some contact. No software.

    I know the part you speak of, we used to use it as a user-selectable backlight color but it was discontinued. Everything is so smart these days, let the controller PWM the color.
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  8. #8
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    Default Re: RGB LED selectable colour

    I've just opened up a small globe which has individual R, G, and B LEDs, which can be sequenced manually by pushbutton...alas it uses a COB chip without markings.

    I've also opened up an RGB LED Christmas bulb ornament which uses IR remote. It has 8-pin chip with no markings. I was hoping to find if it can be sequenced other than through the remote, but if so it's not obvious. No luck here.

    However (OP)!

    I have a cheap dollar-store item which comes close to what you are looking for. It is an RGB fibre-optic "fountain" light which has separate R/G/B 5mm LEDs and runs from 3AA. Colour is advanced by pushing a small button. I have not seen these on sale locally for a few years, but they should be still out there. I will re-check the "dollar stores" around here.

    Small PCB inside has a COB control IC. It should run OK from 5v but I would insert a diode in series (4.3v-4.5v).

    Colour sequence goes:

    R-B-G-RB-RG-BG-RGB(solid)-RGB(shifting) with "off" between each.

    Some limitations:

    (1) Sequence is fixed.
    (2) No direct control over LED brightness (fixed).
    (3) Fixed LEDs not easy to change; small PCB appears delicate.


    I also found a similar light which sits atop a pumpkin, shining down inside to provide colour effects. It's puck-shaped with reflector around the LEDs. Pushbutton could easily be remoted. Product is slightly out of season though!

    Dave
    Last edited by Dave_H; 04-16-2021 at 07:48 AM.

  9. #9

    Default Re: RGB LED selectable colour

    Thanks @dave_H and @DIWdiver

    Some great thoughts in your posts!

    The colour sequence and amount of colours doesn't really matter - I was thinking that actually R>G>B>OFF might be nice and basic, but anything will do as long as each colour can be selectable.

    I didn't think (or know anything) about programming a chip so wondered if there are PICs available that would would be suitable? I am more of a mechanical engineer than electrical, but know the basics and could put together circuits. But I wouldn't know where to start with programming a chip or where in the circuit it would go.

    I've also seen loads of OTS devices - puck lights, halloween props, colour changing pens etc and if I can find something cheap enough that's the easy route to go down. I'm in the UK, where nothing is cheap... but I'm on the lookout!

    I'm just really surprised there's not a PCB on AliExpress or eBay that does this.. even if I needed to add a switch! There are so many toys and gadgets that essentially have the part I need inside them that I am surprised I can't find them on sale anywhere.

  10. #10
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    Default Re: RGB LED selectable colour

    Happy to help out!

    I should add that if fibre-optic part of this cheap ($1.25 in Canada) light is left off, and and plastic case top removed (pops open), the base and PCB are exposed and could be mounted to some backing. LEDs have narrow beamwidth as they normally shine upwards into the bottom of the fibre bundle; this may or may not suit intended purpose. Perhaps a translucent cover would diffuse sufficiently.

    Quick online search found this light from eBay (BTW not endorsing eBay or seller):

    https://www.ebay.com/itm/LED-Multi-C...-/192656165363

    (Funny how the first hits always seem to point to Amazon, Walmart, and eBay...etc.)


    Dave

    BTW there must be "dollar" stores in the UK, but what would they be called...50p stores

  11. #11
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    Default Re: RGB LED selectable colour

    Yes, the PIC16F15213 is the part I was thinking about. It's about $0.38 each at 100 pcs, here in the US. That, three resistors, the LED, and switch are all you need to make a pixel. Oh, and power.

    Is PoundLand the British equivalent of the Dollar Store? Youtuber BigClive talks about them like they are.

  12. #12

    Default Re: RGB LED selectable colour

    Quote Originally Posted by DIWdiver View Post
    Yes, the PIC16F15213 is the part I was thinking about. It's about $0.38 each at 100 pcs, here in the US. That, three resistors, the LED, and switch are all you need to make a pixel. Oh, and power.

    Is PoundLand the British equivalent of the Dollar Store? Youtuber BigClive talks about them like they are.
    Thanks I'll check out that part. It's certainly a step in the right direction and looks like a possible solution.

    Yes Poundland is the equivalent. Full of Chinese junk that lasts about an hour before it breaks! There's always some good electrical bits for hacking though and I'm a big fan of BigClive myself!

  13. #13

    Default Re: RGB LED selectable colour

    Quote Originally Posted by Dave_H View Post
    Happy to help out!

    I should add that if fibre-optic part of this cheap ($1.25 in Canada) light is left off, and and plastic case top removed (pops open), the base and PCB are exposed and could be mounted to some backing. LEDs have narrow beamwidth as they normally shine upwards into the bottom of the fibre bundle; this may or may not suit intended purpose. Perhaps a translucent cover would diffuse sufficiently.

    Quick online search found this light from eBay (BTW not endorsing eBay or seller):

    https://www.ebay.com/itm/LED-Multi-C...-/192656165363

    (Funny how the first hits always seem to point to Amazon, Walmart, and eBay...etc.)


    Dave

    BTW there must be "dollar" stores in the UK, but what would they be called...50p stores
    Thanks for the link. I can get that for £2.57 here so definitely a contender. Cheaper than the puck lights at £5 a piece. I'll buy one and see how it can be hacked.
    We used to have 50p shops, but inflation and all that! Now even Poundland has items that are £2, £5 etc..
    Thankfully Aliexpress seems to be unaffected by the Brexit inflation of everything in the UK at the moment!

  14. #14
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    Default Re: RGB LED selectable colour

    There are lots of PIC projects out there including older 8-pin parts like 16F629 and 16F683. They seem capable of amazing things, difficult to tell if they do anything as simple as manual sequencing.

    For ultimate simplicity, a simple binary counter circuit could sequence through R-G-B-off using a decades-old but cheap and available CMOS chip such as CD4017 or CD4022. Or, you could get the 7-colour+off using a different but still cheap counters 74HC393 or CD4520. A few transistors and other small components would be required, but no software or programming. But, the circuit however simple needs to be on a PCB for what you need, I understand. Perhaps someone has such a PCB out there. Would assembling a kit be an option?

    Dave

  15. #15

    Default Re: RGB LED selectable colour

    Quote Originally Posted by Dave_H View Post
    There are lots of PIC projects out there including older 8-pin parts like 16F629 and 16F683. They seem capable of amazing things, difficult to tell if they do anything as simple as manual sequencing.

    For ultimate simplicity, a simple binary counter circuit could sequence through R-G-B-off using a decades-old but cheap and available CMOS chip such as CD4017 or CD4022. Or, you could get the 7-colour+off using a different but still cheap counters 74HC393 or CD4520. A few transistors and other small components would be required, but no software or programming. But, the circuit however simple needs to be on a PCB for what you need, I understand. Perhaps someone has such a PCB out there. Would assembling a kit be an option?

    Dave
    I'm happy to assemble a kit if I know what parts I need and someone could do me a simple circuit diagram.

    Obviously I'd need a lot of these made up, maybe 200-300 so cost is an issue.

    The cheapest alternative I can think of at the moment would be a capacitive touch sensor PCB (about 20p each) and a white LED all mounted in a 3D printed square 'pixel' with an opaque front. Mount them all in a matrix and when you run your hand over the surface it would light the LEDS on the latching function of the PCB. Press them again to turn off.
    These wouldn't be coloured so more limited in the overall effect and patterns that can be created but price-wise they are spot on. Probably less than £1 per pixel.

  16. #16
    Flashaholic* DIWdiver's Avatar
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    Default Re: RGB LED selectable colour

    Capacitive touch is a cool idea if you can get the things that cheap. Can you post a link? Maybe we can figure out how to incorporate it into the color changing pixel.

    If you can print a housing, that would be awesome! Design it so everything fits nicely, assembly is easy, and away you go.

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    Default Re: RGB LED selectable colour

    Quote Originally Posted by mrmop View Post
    I'm happy to assemble a kit if I know what parts I need and someone could do me a simple circuit diagram.

    Obviously I'd need a lot of these made up, maybe 200-300 so cost is an issue.

    The cheapest alternative I can think of at the moment would be a capacitive touch sensor PCB (about 20p each) and a white LED all mounted in a 3D printed square 'pixel' with an opaque front. Mount them all in a matrix and when you run your hand over the surface it would light the LEDS on the latching function of the PCB. Press them again to turn off.
    These wouldn't be coloured so more limited in the overall effect and patterns that can be created but price-wise they are spot on. Probably less than £1 per pixel.
    It's a lot more than just a circuit diagram. A PCB would need to be layed out with the exact parts you'd be using, then get PCB fab'ed (no doubt in China), acquire the parts, then assembly and test. There's a lot of effort and overhead. What you're looking for likely exists, just a case of finding it. There are alternate solutions you could try out without too much cost.

    The simple counter circuits are just ideas thrown into the mix. For the same end cost you could get something with more flexibility, but not too much complexity. For example with the mixed colours (if that's what you want), something with a bit of PWM control could adjust those colours, otherwise you "get what you get".

    Some other points:

    (1) Not sure how important is brightness and colour-matching among the units. Especially with low-cost solutions, the variation is hard to predict. It would be noticed with modules close to each other, visible at the same time. It's somewhat subjective.

    (2) Anything using pushbutton switch needs some protection from static (ESD) which can kill electronics. Touch switch is an option I was thinking of also.

    I opened up a fancy plug-in LED nightlight (MAX-NL-S1A) which includes a USB charger and other features, which is overkill, plus being too bulky and costly for the OP's usage. But...it manually cycles through three LED colours blue/green/white using a touch pad, so whatever controls this may be of interest.

    After getting past two security screws I managed to partially disassemble the device, but not enough to observe the control circuitry. I'd rather not destroy the working of it as it functions well. If I do find get it open and find an obtainable/useful chip (not a COB), I'll pass this on.

    Dave

  18. #18
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    Default Re: RGB LED selectable colour

    It would be fair to say that projects such as these require a certain amount of "optical" design in addition to
    mechanical and electrical/electronic.

    Depending on desired appearance, LEDs behind a translucent cover should have some level of diffusing to appear uniform. I did a quick check on the cheap fibre-optic light base, using a plastic bulb cover. Irregular circular patterns were formed, different for each colour, with ringed "artifacts", not very uniform. The "mixed" colours are overlapping shapes, not well mixed.

    So this particular low-cost example in itself may not be the best option.

    Dave
    Last edited by Dave_H; 04-26-2021 at 08:34 AM.

  19. #19
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    Default Re: RGB LED selectable colour

    Well, just found yet another dollar-store RGB item which in itself may not be adaptable to the OPs requirement, but convinces me that a solution is out there at reasonable cost. A small round puck with clear faceted lens plugs into smartphone micro-USB port (which is supposed to power it) and should flash in response to music being played; a sort of mini "disco" light.

    Lens appeared to be glued on (no screws), so I gently squeezed it in a vise which popped the glue seal. It came apart cleanly, nothing damaged.

    Small PCB has 8-pin controller chip (unmarked of course), four SMT LEDs (red, green, two blue) and small transistors to drive LEDs. Small electret microphone for sound pickup is mounted on the PCB bottom.

    Device did not work on my phone for some reason, no big deal. I found power connections and attached wires, connected to variable power supply. With about 4v applied, it goes into a slow 7-colour sequence, periodically breaking into a very rapid flashing for several seconds, with no sound input. Sound caused very rapid flashing, and short sound like a clap caused slow sequence to advance one step (neat!).

    LEDs themselves are interesting, resembling large chip resistors with some sort of built-in diffuser.

    With PCB covered by a translucent plastic bulb removed from a LED ac bulb which failed (Philips BTW), light dispersion was very even, including mixed colours, very pleasing effect. Too bad there is no obvious way to manually control the LED sequencing.

    Dave

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