How-to: Picade 12" Screen + HAT + Single Power Source + On/Off Buttons!


#121

Hi

The maximum voltage you can use is 5.2v anything above that could damage the Pi.

I’ve measured mine this morning on the Pi GPIO and it shows on average 4.85v with the volume at maximum. I also tried playing Mario Kart on the Nintendo 64 and there was no change. The undervoltage indicator never shows on my system with this voltage. During boot it dropped to 4.78v which is still above the undervolt threshold at 4.65v.

The problem with using a multimeter is they tend to display an average so its difficult to determine the lowest value without using an Oscilloscope.

The USB cable I use for the Pi to Picade board is the one supplied by Pimoroni. It does seem strange that you are experiencing these issues as I am also running the screen from the same converter that is powering the Pi. Mine is setup up as
PSU -> Converter -> ATXRasPi -> Pi
-> Screen

Did you solder the USB connector on the output of the ATXRasPi if so just check you have no dry joints here.

Cheers

Paul


#122

Hi Paul,

Cheers for measuring yours, really appreciate it :)! Appreciate what you say around a multimeter using averages but it does look as though our numbers are pretty similar, it is weird that I still get an undervolt.

Also tried something else this morning, I wondered if my pi was particularly sensitive to voltage so I tried another one I have which behaved exactly the same way so that rules that out. Good to know you are using the supplied USB cable for pi to Picade, I’m now thinking the problem could lie in the USBs I am using for atxraspi to pi not providing enough power. So I’m on the hunt for the shortest best power rated usb a to micro cables. Any suggestions :)?

I don’t think I’ve got any dry joints on my atxraspi usb output, here’s a photo, what do you think?:

Just out of interest, there were 4 small pins under the usb out but only + and - labelled on the outside of the four on the pcb. Did you solder all 4 joints like me!

Cheers!


#123

Hi

Thanks for the photo.

I did solder all four pins along with the two mounting pins either side of the socket. I would be inclined to try and remove some of the solder as the ball shape you currently have could be hiding a dry joint. You really want to be aiming for a volcano shape around the pins with what would be the point of the volcano at the end of the pin like you have on the boot ok connection.

For the cable between the ATXRasPi and the Pi did you try the one I linked to as that is only 6" long.

Cheers

Paul


#124

Cheers Paul!,

Getting better with soldering but still a way to go :)! I think maybe my iron is not fine enough, I really struggle to get the conical shape always seems to end up like a ball lol! Will see if I can tidy it up, not sure how to get solder off :/!

I’ve ordered one of those 6inch USBs you have so we can see.

One other thing i was thinking I found some packaging for my LCD board that said it needed 2A+ supply, I’ve been thinking it’s a voltage issue all this time, do you think it could be an Amp issue? I guess that may tie in with the Picade drawing more power as volume goes up? They do 12v 6a dc power supplies but would I need a different panel connector?

Cheers!


#125

Hi

There are two methods either a solder sucker or braid.
http://www.maplin.co.uk/p/maplin-de-solder-pump-n40ch
http://www.maplin.co.uk/p/de-soldering-braid-15mm-width-n48fx
The easier one to use is the sucker.

The two are related and if the screen requires 2A+ then that lowers the current available to the Pi which is possibly why mine is ok. If you draw more current than the supply can deliver then the common effect is for the voltage to drop.

If you up the rating of the power supply then you will need to up the rating of the socket as you will be overloading it otherwise. I didn’t look for higher rated sockets than 5A but if you can get Power supplies then you should be able to get a socket.

One test that might be worth doing first is to disconnect the power to the Picade screen and connect the HDMI cable to your TV. Max out the volume and see if the undervoltage occurs. If it doesn’t then you know its the combined current draw if it does then I’m not sure where to go next.

Cheers

Paul


#126

Thanks for the advice Paul! I’ve removed the ATXraspi and cleaned up the solder joints. I’ll test the volume with the hdmi out to a tv rather than the 12" screen. Would it be sufficient to just plug the dc cable out of the controller board (assuming if not connected then there is no current draw?) or would I need to remove the wire completely from the dc panel connectors remove all current draw for the screen?

Cheers!


#127

Sorry I mean unplug the dc cable :)!


#128

Hi

Unplugging the cable from the controller board is all that would be required.

Cheers

Paul


#129

Hey Paul,

Ok so unfortunately it seems to be not what we wanted to see :)! Even when unplugging the DC cable from the 12" monitor and using an hdmi out to a tv I still get the undervoltage sign at high volume (it does seem to be a bit more tolerant but still there). So I guess it can’t be that the screen is drawing too much power. It seems that somewhere between the ac input, dc in, converter, atxraspi, usb cable i am not providing quite enough power to the pi to drive the Picade board fully. As mentioned before if I plug the official pi plug direct into the pi I don’t get the undervolt. If I cut the atxraspi out and plug the converter direct into the pi I still get the undervolt which indicates it is not outputting either enough volts or amps to fully drive the Picade board (although at 5v and 3A it should be). If I measure the dc panel connector pins they are providing 12v in. Am at a bit of a loss to the cause. Still waiting for the 6inch usb cables you used to arrive to see if that makes a difference but not hopeful if the converter itself doesn’t provide enough power to drive the Picade board. Could it be a problem with the Picade board?, although I guess it wouldn’t be fixed by plugging the official pi plug straight into the pi if that were the case. Have also tried a different converter from a different manufacturer with no better results.

Cheers!


#130

Hi

It would appear that it is the converter though the one I bought was nothing special and it came from eBay.

http://www.ebay.co.uk/itm/DC-DC-Converter-Regulator-12V-to-5V-3A-15W-LED-Car-Truck-Camper-In-UK-/142414851597?hash=item2128962e0d

The only difference is that the one I used just had bare wires which are a similar size to the input size.

The amp used on the Picade board is quite power hungry.

Cheers

Paul


#131

Cheers Paul,

It may well just be something I have to live with, am interested to see if I get the same issue with my next build. Just wanted to say thanks again for all your help and support it is really appreciated.

I have ordered some of the converters with just the wires to see if that makes a difference, I suspect not as others have used the ones with micro USB, @Luis would be interesting to know whether you experience any undervoltage issues as you have used the same style converter (just out of interest what rating is your dc power supply?).

Will let you know if I ever get it sorted :)!!

Thanks again!!


#132

Hi

No problem.

Cheers

Paul


#133

Cheers Paul,

One last question I promise lol, what ac power supply are you using?


#134

Hi

This one but in black
http://cpc.farnell.com/powerpax/sw3101-wh/power-supply-12vdc-5a-white/dp/PW03810

Cheers

Paul


#135

I have never had any issues with under voltage but then again I never blast the volume at full power (my wife would kill me). Yesterday I played some games at full volume and did not get the lightning bolt signal.
I have a 12v 4a power supply that I found at work and never had any issues with it.


#136

Cheers Luis :),

Thanks for letting me know. It’s really strange it just seems to be a limit of my system somewhere I’ve got another converter I can try and some different short USB cables on the way. When I’m soldering my converter and screen cables to the DC panel connector I’m soldering them to opposite sides of the connector, did you twist your cables together or anything before soldering?

Spent so much time and money trying to get rid of this damn lightning bolt, I think my wife is about to kill me :)!!

Cheers


#137

Hey @MrScruff I take it back. Today I was playing AvsP and when I blasted the volume I got the lightning bolt to show up. I guess it maybe depends on the game. Also the image that I got has a video intro that when I turned the volume way up it shows the warning sign. Like I said; I never play the games a at very high volume anyway so it’s all good for me, I can live with it.


#138

Hey Luis,

Thanks for coming back to me to let me know, sorry you also got it but I guess at least now I know it’s not just me or something I did lol! Yeah I agree it seems to be system and game dependent, if I limit my alsamixer to about 80% i generally don’t get it unless it’s just a particularly taxing game. I have lost count of the number of different components I’ve tried to get rid of it lol, i think it’s just something I’ll live with. I agree never going to have the volume that high anyway!

Cheers!


#139

It seems as though I missed a lot… all caught up now.

I too have the under voltage warning. Mine doesn’t seem to be tied to volume though. I get it mostly at boot up and shutdown.


#140

I hope some of you guys are still here. If I wanted to use a ATXRaspi with a momentary switch, how do I wire power to the monitor, such that it does not stay powered up all the time? I get that for the PI, the momentary switch will then signal atxraspi to send power to the PI, but the remaining 12V lead to the 12.1" display controller needs to get power somehow. Is that why you used the latching switch?