SMPS based power supply for Raspberry PI 3 Model B

[sugandha123]

Hi

I want to use SMPS for Raspberry Pi 3 Model B and display but we need type B usb cable for supply.
How can I customize USB cable for it?

I have cut the one USB cable and there is 4 wires.
1. GND
2. +5V
3. Data+
4. Data-

I have connected GND to the GND of SMPS and +5V to the 5V of SMPS. And gave power to RPI and display but after sometimes display is showing low battery and Pi got heat.
I am using 5V 10A SMPS. RPI takes 2.5V/3A
Display takes 2.5V/3A.

Can anybody tell me the reason?



Thanks

 

[d123]

Hi,

Not sure, maybe the USB cable is not suited to such high current, nor the connector.

USB

How USB Charging Works, or How to Avoid Blowing Up Your Smartphone

Maybe cutting data connections is not a wise idea. The Pi may expect intelligent power communication, not dumb SMPS wires.

Don't RPi devices have the option of a barrel jack connector for the power supply?

Sorry can't be of more help.

 

[KlausST]

Hi,

What do we see at the pictures?... a lot of cables, but not how they are connected and what wire gauge they are...

Are you sure the RPi amd the display are specified for 2.5V?

Klaus

 

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USB type b cable was never meant to supply 3A let alone 3A to two different device at the same time (6A), a standard usb cable is good for maybe 1.5A and those shipped with cell phones that have fast charge are good for double that. Past that the cell phone chargers up the voltage to keep the current through the cable at 3A max. Unless you have some special power USB cable your cable is not likely to last.

 

[MD_SHAHRUKH]

I am confused about the display connection. What is the display which is been used here? Is it connected with the HDMI? And as far as I know, the Rpi-3 model-B uses a micro USB connection for input power supply. Please clarify what is the display here and show us you overall loads connected to Rpi.

Regards.

 

[sugandha123]

I am confused about the display connection. What is the display which is been used here? Is it connected with the HDMI? And as far as I know, the Rpi-3 model-B uses a micro USB connection for input power supply. Please clarify what is the display here and show us you overall loads connected to Rpi.

Regards.

We are using 10.1 inch touch screen display which is connected to RPI 3 model B through HDMI and Touch USB cable.
And MAX232 is connected to Raspberry Pi for serial communication.
We use these components for vending Machines and display is used for runnng app.

 

[MD_SHAHRUKH]

We are using 10.1 inch touch screen display which is connected to RPI 3 model B through HDMI and Touch USB cable.

If the power supply is separate for the Display. then there will be no issue, the raspberry will not supply through the HDMI. If not connected separately, I will recommend you to connect it using a separate cable to power the Display and RPI.

If it again shows the power deficiency at the raspberry side, Then I recommend you to check the MAX232 again, is the MAX IC is heating up? There is a lot of chance the current is draining somewhere.

Can you share max232 ic to RPI connection?

 

[sugandha123]

If the power supply is separate for the Display. then there will be no issue, the raspberry will not supply through the HDMI. If not connected separately, I will recommend you to connect it using a separate cable to power the Display and RPI.

If it again shows the power deficiency at the raspberry side, Then I recommend you to check the MAX232 again, is the MAX IC is heating up? There is a lot of chance the current is draining somewhere.

Can you share max232 ic to RPI connection?

I am using SMPS for both the supplies.
Output of SMPS is +5V,10A.
My question was what type of cable should we use for connecting power through SMPS for RPI and display.

Connection of MAX232 to RPI
RPI-----------------------------> MAX232
+5V-----------------------------> +5V
GND----------------------------> GND
Tx--------------------------------> Tx
Rx-------------------------------> Rx

 

[MD_SHAHRUKH]

You can do this connection and make a further connection by using a standard mobile charging cable. I do not think your load requires that much current, you are using Display and RPI which can operate within 3A. 10A supply is more than sufficient.

 

[KlausST]

Hi,

For that high power requirement I'd use cables with high wire cross section...and connect it via 2x GND pins and 2 x 5V pins on the GPIO header to the RPi.

Tx--------------------------------> Tx
Rx-------------------------------> Rx

MAX232 (MAXIM datasheet) has neither Tx pins nor Rx pins.
--> If you want us to validate your wiring you should use exact names.
Otherwise we have to guess whether you used the correct pins or not.

Klaus

 

[sugandha123]

View attachment 157622

You can do this connection and make a further connection by using a standard mobile charging cable. I do not think your load requires that much current, you are using Display and RPI which can operate within 3A. 10A supply is more than sufficient.

Yes.
Display takes 3A, RPI takes 3A and we connect dongle sometimes for internet so we have purcahsed 10A SMPS for this.

 

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Still USB-B connectors (not just the cables) are not rated for more than 30V 1.8A. Hence why I mentioned previously that the fast charging for USB uses a higher voltage and keeps the current at 2A max.

USB-B cables/connectors are not good for supplying 6A at 5V, figure out a better method of connecting the power.

 

[sugandha123]

Still USB-B connectors (not just the cables) are not rated for more than 30V 1.8A. Hence why I mentioned previously that the fast charging for USB uses a higher voltage and keeps the current at 2A max.

USB-B cables/connectors are not good for supplying 6A at 5V, figure out a better method of connecting the power.

But Raspberry Power adapter with cables provide upto 5V, 2.5A current
So if we remove power adapter and use SMPS then why it will not work?

 

[KlausST]

Hi,

You sure are aware of Ohm's law and power calculations.

When you increase the current from 2.5A to 6.0A on the same ohmic load (like contact resistance at the USB connector or wiring resistance).
You get about 5.8 times higher power loss = 5.8 times higher tepmperature rise.

So if the temperature before rises from 20°C to 40°C it will now be 135°C.

Klaus