GeekCreit Rainbow Clock Kit Problems - Page 1
Forum section: electronics / projects

author: Websteria
author_rank: Contributor
timestamp: August 20, 2019, 01:53:36 pm
content: Hi all! I've just finished putting together the GeekCreit Rainbow Tube SMD LED Clock. The red and blue elements on the LEDS are lighting up but the green element seems to not as the clock only cycles between green and red and is supposed to be full rainbow color. As these are simple devices with an STM processor I was wondering if maybe I didn't get all 44 leads soldered down. I think I'm going to wait for my microscope to check those.Link to product:https://www.banggood.com/Geekcreit-Large-Size-Rainbow-Color-Digital-Tube-DS3231-Clock-DIY-Kit-p-1323917.html?akmClientCountry=America&cur_warehouse=CNLink to Manual:http://files.banggood.com/2018/07/1323917.docSince these are 5050 LEDS I'm wondering if they daisy chain the info or if it's possibly a pin on the processor, or did I miss a pad on all 60 LEDS. Sadly I don't have the schematic or I could easily figure this out. Please help. I'm happy to provide more information.I have another clock I put together like this but the buzzer just clicks. What usually feeds a buzzer? would it be a triode?Thanks much!Jeff

author: ledtester
author_rank: Super Contributor
timestamp: August 20, 2019, 03:58:48 pm
content: I have a feeling they are smart addressable led modules like a WS2812. See if the pinout looks right:https://cdn-shop.adafruit.com/datasheets/WS2812.pdf

author: Websteria
author_rank: Contributor
timestamp: August 20, 2019, 07:21:33 pm
content: No, these are just standard 5050 three led in a row smd leds. What I also meant to say is that the blue and red work but the green doesn't. If I used my diode tester inline some of them light up red, and that's it. If I had a short in just one of the leds would that cause the entire green channel not to work for all of them?+ ->| -+ ->| -+ ->| -This is how they connect electrically. Diode tester wouldn't have given me a forward voltage if they were WS2812s.

author: OM222O
author_rank: Frequent Contributor
timestamp: August 20, 2019, 07:45:54 pm
content: non of the green elements light up? sounds like a drive issue more than anything else.you said you tested the leds with a diode tester and "some of them light up red", what's the pinout? which ones you tested?A short could be possible to, but that's easy enough to check with the resistance mode ...

author: Websteria
author_rank: Contributor
timestamp: August 20, 2019, 11:11:04 pm
content: I need to go back with my meter and test the diode voltages on one off the board compared to one on the board. So you think it’s either the processor leg that controls that segment or ... what other part of this clock would be the driver circuit? It only has the main stm chip as well as the rtx chip and one transistor. I will check voltages and post more as well as a picture and video of how the leds react.

author: OM222O
author_rank: Frequent Contributor
timestamp: August 21, 2019, 01:02:32 am
content: I'm not sure since they do not provide any details in the manual you linked. no schematics, no part numbers for the leds, no nothing! without having the circuit in hand, it's impossible for us to tell why. if you say there is only the MCU,the RTC chip and a transistor, then that means the MCU must be supplying all of the current for the leds? that doesn't sound right. the next best thing would be that LEDs are digital as suggested before, so check if they have a connection to the positive supply. another thing you can check is the connection between the MCU pins and the leds. how many pins are connected? are they serial line pins or generic io? there's just too much information missing for us to tell anything.

author: Websteria
author_rank: Contributor
timestamp: August 21, 2019, 01:50:11 am
content: There’s a lot of small resistors and capacitors on the back. I have another board but I have no idea how to create a schematic from a board. Based on my testing they aren’t digital leds. I’m wondering if the line driving the green leds doesn’t have a cold solder joint somewhere. They’re all wired independently.

author: Websteria
author_rank: Contributor
timestamp: August 21, 2019, 12:41:43 pm
content: Here’s a link to show the problem.https://youtu.be/c1D23Q4-DPw

author: Websteria
author_rank: Contributor
timestamp: August 21, 2019, 01:39:03 pm
content: Ok. I used my bench power supply to give 5v and 20ma of power. As suspected the green led terminal lit the red led. This means there’s a short between the red and green terminals on one of these tiny leds. I reaoldered all the anode sides with flux (grounds are tied together) with no luck. They’re all in the same circuit so it seems.

author: OM222O
author_rank: Frequent Contributor
timestamp: August 21, 2019, 06:25:05 pm
content: a short could be possible. but as I said earlier, instead of trying to find the short by applying voltages / using diode modes, try using the resistance mode.measure the resistance between one of the green led anodes and:-The anode of another red led-Ground-Driving pin on the MCUand then post the results.The first one tells you if there is a short between the green and red leds, the second tells you if the green leds are shorted to ground and the third verifies correct connection between the MCU and the green leds (you should be able to read the current limiting resistor value between the two).