From your pic, I don’t see an “open GND on the top right…”.
There is one directly opposite (lower right) the ground you’re using and yes they should be connected internally on the board. You should be able to use either.
As far as power supply connections, I would suggest that you connect your PS DC grounds together on the supplies not on the ESP32. You can use a separate data wire with accompanying ground wire connecting to the levelshifter and then your LEDs.
As mentioned before, clean simple wiring of the 74AHCTxxx is important.
Using the bypass cap and neatness both count. The resistor is the last thing I would worry about.
Overall, that’s the right idea for the 74AHCT125 but some notes:
The bypass capacitor must be on the perfboard as close to the power pins as possible.
Normally you place it “above” the chip so that one pin is right next to Vcc (pin 14 on the chip). Solder that up and then use a short piece of wire to bridge to the nearest grounded pin (in your case pin 1 is grounded so that’s convenient).
Best practice is to use a single 5V and a single Gnd connection to the board. Jumpers of Gnd and power between the pins are done with (very) short links. Unneeded long wires are not your friend. Remember, these are data connections and don’t require any (appreciable) power handling. You can use very tiny (24AWG or smaller) wires.
I mentioned the alternate wiring diagram as it uses Gnd connections for all the unused inputs rather than +5V and Gnd. It will work properly with the '125’s and I find it easier to wire on perfboard. As well, if you end up using multiple GPIOs (and even if you don’t), that diagram shows how you can use provide more than one data line to your LEDs.
Driving each strip from its own data line rather than tying them all together is a much better practice. You can still tie all the levelshifter inputs together so they appear the same.
I would get rid of that yellow dupont wire and use something a little heavier. I could easily see having a bad solder connection when using that as there is very little wire in those to make good contact with.
Good point Jinx, I used what i had.
Now have true copper wire 0,25mm²
Will solder new board tomorrow using coper only.
Divsys thanks for another reply!
Will place capacitor over pins 1 and 14 on the new board
Also found out my 5V convertor board (no potmeter to be found) outputs 5,2V might be an issue?
You mentioned the alternate wiring diagram but i’m not sure what diagram you are referring to.
You suggest not Connecting power on the unused xOE port?
Then which of the unused ports should i ground?
xOE
xA
xY
Will make new board with beter and short jump wires.
Will post, thanks for your help.
If this project comes to life my ceiling will consist of 1620 5cm “neon” leds, can’t wait to experience that. Since there are that many light sources i’m expecting little to no shadows which must look special “studio” like in your own living room.
On the KB Levelshifter page, there’s a section “How to connect Levelshifters”.
The first diagram is labelled as 74AHCT32, but it will work exactly as shown for 74AHCT125’s as well.
The only unused pins you need to worry about are the xOE’s and xA’s. The xY’s are outputs and can be left alone.
You’ll note that diagram also indicates how you can use more than 1 channel for driving LEDS.
As I mentioned, you may be better off in the end by using 1 channel to drive each strip and connect all the channel inputs to the same GPIO (or 4 separate GPIOs).
I have this exact same black strip. I am having zero luck getting it to work. Also bought the 74HCT125 for level shifter. Using an EPS32 WROOM. I’m about ready to give up on these strips. What is a reliable strip of LEDs I should use instead?
