Hey, I have this screen connected to a Raspi4, does it need a separate power supply to the Raspi? I tried plugging it into the USB port on my laptop but get some screen flicker on the display of the 8.9.
Hi Stuart,
We were trusting DFRobot on this one. We’ve been able to reproduce the issue on various Pi 4s and a Pi 3B+. It seems the display is drawing too much current on startup, dropping the 5v rail down to around 4.7v (so it shuts itself off), then when it comes back up to 5v it tries to start again.
The manual for this display does state a minimum power requirement of 5v/1A but it seems it requires a lot more on startup. We’ve got a bit more testing to do, so we’ll update you as soon as we know more.
For now, if you can power it externally they are gorgeous little displays. We’re very sorry about the misinformation!
Regards,
Oliver
Support | Core Electronics
Hi Stuart,
I’ve completed some more testing. I’ve seen a peak current draw of 1.46A at 5v. A Pi 4 is only rated for 1.2A so it’s definitely pulling more than a Pi can supply to run, not just on startup.
By connecting it to an external supply first, then lowering the brightness setting you can get the power draw down, allowing it to then run from a Pi without an external supply. I was able to get it working reliably on a Pi below about 20% brightness with nothing else connected to the USB ports and no audio playback. If you need sound the brightness limit will be even lower.
You’ll need at least 1.5A available to power this display from 5v for full functionality. We’ve updated our product page to reflect this.
We did have a diagram on the product page showing it could be powered by a Pi without an external supply as per DFRobot’s specifications (we’ve now updated the page) so if this change to the power requirements changes your need for the screen, please send us an email and we’ll work with you to sort it out.
Sorry about the mix-up!
Regards,
Oliver
Support | Core Electronics
Hi Oliver
Thanks for your testing, its not a game changer.
I can power the display while portable with my Goal Zero Sherpa 100PD (up to 5v 3A), all I need now is for the pi-juice hats to come back in stock at Core to power the Raspi!
Cheers
Stuart
Hi Stuart,
No worries! That’s what I’m here for 
Re the Pi-Juice hats, Pi Supply are currently doing a production run. They should be available again in a month or so. In the meantime, I’d suggest signing up for product notifications on the product page - that way you’ll get an email as soon as you’re able to place an order for one.
Regards,
Oliver
Support | Core Electronics
