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Trying to Power Pi, LCD Screen, and Thermal Printer
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Trying to Power Pi, LCD Screen, and Thermal Printer

by gmpmovies on Sat Aug 17, 2019 12:34 pm

Hey I just purchased the 5V 4A (4000mA) switching power supply, the Panel Mount 2.1mm DC barrel jack, and the 4700uF 10v Electrolytic Capacitor (order #2109405 I believe) to build something very similar to the IOT printer found on your website. My end goal is to power the raspberry pi (which is also connected to a camera module), mini thermal printer, and the raspberry pi 7" LCD touch screen through the DC barrel jack so that I don't have tons of power cables coming out the back. I've tried a few different configurations in order to supply enough power, but it seems that no matter what I try, the raspberry pi gets only about 4.15V and shows me the low voltage warning (and when I try and run the GUI application that I wrote, it will slowly fade the screen to black and then the pi will reboot). Initially, I wired the DC barrel jack to a rugged on/off push button and from there I supplied power to the printer, rpi (through the GPIO pins), and touch screen. Note that I was using jumper cables and a breadboard to connect everything together, I don't know if this would have anything to do with it, I'm very new to the hardware side of technology and electronics and don't understand how electricity works very well. I then spliced a micro usb cable, and then soldered that to two jumper cables hoping that would provide a more reliable current, however same thing happened. So I connected JUST the raspberry pi directly to the DC barrel jack but continued to only receive about 4.15V to the raspberry pi.

After that I disconnected everything from the raspberry pi, and tested the ends of the wires that plugged into the raspberry pi and they tested at 5.15V.

Is there something I am missing, or a reason why I'm experiencing a voltage drop the second I plug something into the DC barrel jack?

Thank you for your help!
Attachments
58753685027__20748D6F-6645-4A8E-92FB-BCCC914FACED (1).JPG
From there it plugs directly into the rpi.
58753685027__20748D6F-6645-4A8E-92FB-BCCC914FACED (1).JPG (164.53 KiB) Viewed 42 times
58753682626__09F8F632-718F-4614-A42E-13FB86689868 (1).JPG
From there I had power going to just the LCD screed and the raspberry pi (I did not have the printer connected to power in this moment). You can see the spliced micro usb cable that I've connected to in the bottom.
58753682626__09F8F632-718F-4614-A42E-13FB86689868 (1).JPG (119.46 KiB) Viewed 42 times
58753679486__D6E0E667-FF82-4F53-95B0-DEF9FA3E1ADF (1).JPG
Here is where the DC barrel jack attaches to the breadboard
58753679486__D6E0E667-FF82-4F53-95B0-DEF9FA3E1ADF (1).JPG (155 KiB) Viewed 42 times

gmpmovies
 
Posts: 2
Joined: Fri Aug 16, 2019 11:10 pm

Re: Trying to Power Pi, LCD Screen, and Thermal Printer

by adafruit_support_mike on Mon Aug 19, 2019 12:24 am

The power supply should be able to run any RasPi comfortably.

It's hard to tell from the photo, but have you soldered the red and black wires to the lugs on the round barrel jack? Wrapped wire doesn't make a very good electrical connection, and you could be seeing a lot of loss that way.

adafruit_support_mike
 
Posts: 59131
Joined: Thu Feb 11, 2010 2:51 pm

Re: Trying to Power Pi, LCD Screen, and Thermal Printer

by gmpmovies on Mon Aug 19, 2019 12:30 am

Yes the wire is just wrapped around the barrel jack and is not soldered in. I didn't know that this would cause power loss, thank you for your input. I will try soldering the inputs and see how that works!

Thanks!

gmpmovies
 
Posts: 2
Joined: Fri Aug 16, 2019 11:10 pm

Please be positive and constructive with your questions and comments.