MAX7219 8-Digital Segment Digital LED Display Tube for Arduino 51/AVR/STM32

5 stars because all 5 of these were cheap, not irretrievably bad, and serve my purpose. HOWEVER: You need to know: 1. Carefully inspect the back. On mine, I found several questionable solder joints to the two displays. It seems the SMDs (7219,C1,R1&D1) were machined reflowed (perfectly) but the two displays were then hand-soldered, some crookedly and not terribly carefully. Those that were crooked I desoldered and resoldered flush, and touched up all the other display solder joints. 2. Remove diode D1, and short its pads with a wire. It serves only to protect against reverse polarity. Fine, except it’s inline to the daisychain VCC out, so will drop 5v too much to any daisychained displays. 3. I added a 10uf electrolytic across VCC & GND, as close as possible to the input & 7219. It, along with C1, helps decouple 5V load spikes as the LEDs change state. The pos leg of my cap serves to short the D1 pads. See the pic. I used a 50V 10uf ‘cause that’s what I had, but a 25V one would be even smaller. 4. The 7219 chips on all 5 units were *completely* unmarked. My guess would be that these are, at best, clandestine “overnight overruns” of legit runs of Maxim/AnalogDevices. Or, of course, total clones. The price of legit MAX7219 SMDs in quantity is multiples of what we’re paying for these entire modules. Nevertheless, the chips appear to work fine albeit quite warm at full load (8 digits on at intensity 15). 5. Finally, the overall design of the board leaves something to be desired. There’s no way to abut these modules to create a seamless 16, 24, etc digit display. Enjoy.

Do not buy - I received non-working displays and spent more time figuring it out than I saved by buying cheaply from this seller. Very disappointed.

I ordered 10 of these to use as part of building a physical radio stack for a Cessna 172 in Microsoft Flight Simulator 2020 using MobiFlight and an Arduino. Pros: * They are cheap * They ship fast * They work with MobiFlight right out of the gate Cons: * One of the 10 boards I received didn't work properly * Each board has a diode on it to guard against +5V/GND being swapped, but this diode cuts the voltage so much you can't daisy chain beyond two boards and in my case also prevented them from working when connected to an Arduino via a breadboard. If you plan on using these I recommend removing the diode and replacing it with a small piece of wire. It takes no time at all to do and makes these actually usable in a daisy chain situation: I have six connected in series with the diode removed and they work great. Also plug each display directly into +5V/GND and only daisy chain the three control wires. I strongly recommend methodically testing each board upon arrival as well to save yourself a TON of heartache trying to figure out why things aren't working. Solder the connectors on all the boards and then: 1. Test every board in isolation to ensure it displays properly. Mark the "in" end of each board as OK. 2. Take a board with a known good "in" and use it as the second board in a daisy chain. Test every board as the first board and verify both boards light up correctly. If this works then mark the "out" of each board as OK. In my case I had one board that didn't work properly for "out", and regardless of where it was in chain it would cause havoc with the other boards.

I'm using several of these daisy chained to ESP32 hardware for a simple display. I'm using the "universal" LED display driver C++ library "By HKJ from lygte-info.dk". So far all of the modules I have hooked up have worked correctly out of the box (none of them had soldering or LED alignment issues). They seem quite bright for this type and size of display. As others have mentioned, it is best to feed each module (module = 8 digits) with its own +5V and ground supply, and only daisy chain the data, strobe, and clock lines. This will avoid feeding power through multiple polarity protection diodes which will cause a significant voltage drop with each added 8-digit module in the chain.

Nice display solution for Arduino or other MCUs.

Received 5 . None worked to receive power and there were very visible cold solder issues . I resoldered them all and now they are all working.

As others have said in the reviews jump out the diode. The voltage drop it causes will give you grief so yes jump it out! it is wired in series with the 5volt supply so removal and soldering a wire to jump the two pads is the way to resolve this. Some talked about the digits not being properly aligned, I bought ten units and all are not properly aligned, all the same, all out of alignment, but it is possible to heat up the solder and align them.

I tested all 5 units and initially found that 2 were defective and after a short time would become erratic in what was displayed. I continued to test the remaining 3 and now they are defective also. I had a previous order of 4 of these units (another supplier) and two of the 4 worked just fine. I should have kept them as now I don't have any that work. Returning these to Amazon.

Nice product .Works just fine

Very good for retro looking projects. All 5 were perfectly functional, I had to desolder one and resolder and the pads held up fine, so a good quality PCB. I used with both 3.3V and 5V, they are pretty bright on 5!!

4 defective doa out of 5