开云体育

Dear all folks,

I've been trying for any means to mate this LCD screen to my RPi4 with no luck. https://www.waveshare.com/wiki/7inch_HDMI_LCD_(C)

I am about to give up after tried almost every google suggested configuration (pre conf files, odd screen set ups, different raspbian OS's, Raspberry Pi for Hams, config file from scratch following wiki instructions, etc)

Any of you with a story of success? Am I omitting smt basic? LCD works fine with my laptop as second monitor with both Ubuntu and win10 and RPi4 works fine with an external LCD screen.
I welcome all your ideas.

73 de Carlos, 2W0YVY

Just checking...did you follow all the? (long) instructions listed on the "Raspberry Pi" tab on?https://www.waveshare.com/wiki/7inch_HDMI_LCD_(C) ?
Are you running Raspbian or the aarch64 OS? Did you try it using an SD card with Ubuntu on it?

Big enough power supply?? I notice the web site explicitly labels the power input at "5v 3A"

A description of "doesn't work" would be helpful.? Doesn't light up? Display unreadable?

"No signal" error?

73

John

John, maybe this will help: The "official" power supply for the 4B is
5.1v., 4 A. A power supply for the 3B+ I have found by trial and error
is a 5.25 V., 3 A. This will keep you from getting "low power, check
power supply" messages and the little lightning bolt on the upper
right corner of the screen.

Agree with the above comments. The power supply for the Pi4 is fairly critical. I've seen issues with my LCD display when running off a battery, which then promptly went away with using the "approved" adapter. Try that first.

Thanks,
Bruce

At 3/7/2022 16:33 UTC Charles Albert wrote:

John, maybe this will help: The "official" power supply for the 4B is 5.1v., 4 A. A power supply for the 3B+ I have found by trial and error is a 5.25 V., 3 A. This will keep you from getting "low power, check power supply" messages and the little lightning bolt on the upper right corner of the screen.

What is this thing with available "official" power supplies being capable of no more than the Pi requires? Why not make one capable of say 6 amps (or even more) and a short/heavier cord to reduce voltage drop? From the comments here I bet something like that would be popular.

JimH

you betcha, especially the cords.

Marty kd8bj

Hi,
I agree. I have an official RPI supply and got the low voltage warning (on RPI2,3 and 4).
Checked the voltage and it shows 5.14V. Current consumption was about 1A.
I bought one of these of the auction site?
Tweaked the voltage adjuster up and the warning disappeared at 5.18V, so I set it at 5.22V. No more warnings.
The voltage readings are relevant to the multimeter I use and won't be the same as anyone else. It hasn't been calibrated to a standard. That's suggests a project to construct a 'standard'

At 3/8/2022 09:54 UTC G8HAV wrote:

I bought one of these of the auction site <>5A DC-DC Voltage Step Down Buck Converter Adjustable XL4015 +Heatsink _UK Fast, and set the output to 5.14V, sure enough 'low V warning'.
Tweaked the voltage adjuster up and the warning disappeared at 5.18V, so I set it at 5.22V. No more warnings.

I suggest connecting a 5-ohm or even a 1-ohm load across the output (no R-Pi) and then measuring the voltage. Run it until the regulator gets uncomfortably warm and if that happens very quickly maybe it isn't quite as rated.

For ham radio, SSB, a power supply capable of say 20 amps, but not continuously, works fine for a 100-watt rig because SSB is maybe 100-watt peak but 25-40 watts on average. For continuous duty, like running a computer, the supply rating needs to be continuous. These little wall warts are pretty much consistently overrated... tho I think the "official" ones are generally better... except for the cords... too thin, too long.

I also think the "official" suplies are rated to run the R-Pi, not everything you might quite logically want to connect to it. There needs to be 1.2 amp set aside JUST for current from the USB ports. More for hats. And then some headroom.

The voltage readings are relevant to the multimeter I use and won't be the same as anyone else. It hasn't been calibrated to a standard. That's suggests a project to construct a 'standard'

A zener diode in series with a resistor and a 9-volt battery. Measure across the diode on a good, calibrated meter and then it's a decent single point standard as long as the battery is good.

73 de Jim, KB3PU