Cold LEDs/7-Segments inoperable and observations on lifespan


I have made A LOT of progress and a significant time investment into a project creating some really awesome gauges for my car. See videos below: (also see attached pictures for construction)

They work great immediately after installation, but I am having reliability issues, which is really discouraging me from continuing the project. I am looking for advice on how to make these more reliable.

Both projects share similar components, similar programming (copied portions), and similar design strategy.

The only differences are:
-Dome light gauge I think has more expensive 7-seg displays and board by OSHpark
-Round gauge has almost all made in China LEDs/7-segs, board by SeeedStudio. It is a two part board and has two MAX7221 linked together to control all the tons of LEDs.

Relevant Components include:
-Arduino (Pro mini 5v version)
-3-digit 7-segment Common Cathode (some from China cheap, some from DIGIKEY $$$)
-Bi-Color LED common cathode 3mm LEDs from china, cheap
-Circuit boards by SeeedStudio (boost gauge)
-Circuit board by OSHpark (the 3x 3digit/7seg dome light gauge)
-All soldered connections
-Chinese buck/switching power supply (same for all) 12v->5v


  1. Cold Start reliability:
    On a cold day, the 7-segments will refuse to light. They will remain unlit until power is cycled, AND the environment is warm enough. On a nice spring/summer day they will light the first time and remain functional.

The the dome light gauge is more likely to light on a cold day, and seems to be more reliable. The circular gauge has the worst reliability. Works well in the warm environment, either initially or after the restart.

  1. 3mm LED failure
    A few of my 3mm LEDs have failed. The failure is every 4th led (which seems to indicate a connection issue more than an actual failed LED)

*** I previously purchased a cheap water temp gauge, disassembled it and remote mounted the 7-seg far away from the “brain” of the gauge using a ribbon cable. it had crappy cold start characteristics also. But was a finished product, from China***

I assumed LED technology would be good enough that any manufacturer would make a quality product. All LEDs are powered/regulated by the MAX IC chips…

I did plan on trying to market these but they are far from being polished enough to do so.

My suspected issues are:
–LED manufacturer quality (ability to operate in “extreme weather” temps -20F-120F)
–Assembly skill (my-error)

Any input or opinions/experience with similar issues on your LED projects?




Have you considered the possibility of your MAX7221-chips being fake counterfeits? That could be the problem.

The MAX7219 is heavily copied: Fake chip investigation

LED's are very durable if driven properly. If you cook them with too high current, the bonding-wire can break from thermal stress and give intermittent operation. If you adjusted the current to be within the limits of the datasheet, i suspect the problem is the chip overdriving them, or just failing itself all along.

// Per.

When I worked for General Motors, we had to purchase components rated for the automotive industry. I highly doubt that your components would pass muster.

OK. So a knockoff MAX7221 could be temperature intolerant?

I did buy a bulk pack off of eBay from china so that is highly possible.

Now that I know what I am doing and have made several prototypes, I am ready to splurge a bit on the electronics to ensure reliability.

Are Digikey/Mouser etc... reliable sources for "legit/authentic" components? Or how else can I guarantee they will be authentic besides verifying via your link post purchase?

Gslenk: Are Digikey/Mouser etc... reliable sources for "legit/authentic" components? Or how else can I guarantee they will be authentic besides verifying via your link post purchase?

Digikey or Mouser should be fine.

I buy ICs on eBay, because what I am doing is for "fun" as a learning exercise.

When I worked for a major defense contractor, the issue of counterfeit ICs was heavy on the mind of the purchasing manager. Imagine ICs that went into space not working.