WS2812 and PSU interference

[paulca]

So I built a little WS2812 RGB LED controller with an ESP8266 and 75 series TTL bus transceiver to level shift to 5V.

It works perfectly fine... until I connected it to the 10A 5V PSU I bought for the job.  The LEDs flicker and flash. 

But it gets weirder.  I connected the LED controller back to the bench supply and the LEDs still flickered.  If I turn off the PSU ... or if I pick up it's disconnected barrel jack and hold it, the LEDs stop flickering.  So the PSU does not even need to be connected to the LED controller to make the LEDs flicker, it only needs to be on and in the vicinity. 

Doubtlessly this is a switch mode PSU, I scoped it's output and it has some ripple as you would expect, but it's nothing severe.  I expect it has some mains leakage which is freaking things out and when I grab the barrel jack I am absorbing/dissipating some of the noise.

The question is, other than trying more PSUs (and beefy ones aren't cheap!), how can I emulate the effect I'm getting by connecting myself to the PSU ground, which stops the LEDs flickering?

I did put a 220uF cap across the power rails, but it had no effect.

[paulca]

Never mind.   

I had a feeling that when things work different depending on whether you are touching them or not, it's usually a ground connection issue.  I measured resistance across the ground points on the circuit and found the enable pin on the bus transceiver had a dodgy connection.

[Sonny_Jim]

Just a quick tip which you may already know, but keep the data line from the transceiver to the start of the string as short as possible.  Depending on the string type, anything longer than 10-20cm and you'll start to have strange results.