R-A
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unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 1:16 pm

I have a Meanwel HDR-30-5 DIN Rail power supply for my Raspberry Pi 3+ Model B, but the power seems to be a bit unstable.

According to the [ur=http://www.mantech.co.za/datasheets/pro ... -SPEC.pdfl]datasheet,[/url] it can deliver 5.5V @ 3A, yet I'm seeing volt drops, down to about 4.7V. I have a DMM connected to the output of the PSU the whole time to measure it. The output from the PSU goes to the VIN PINS of the Pi.

While playing music from Youtube, I often see the yellow lightning bolt in the top right corner of the monitor, and it often reboots due to the power loss.

Why the DIN rain power supply? I use the Pi to monitor my inverter, house energy consumption and some DS18B20 temperature sensors in the garage. There isn't a power outlet in the DB board, where I mounted my Pi using a DIN rail case like this one


Does anyone know if it would help if I put a capacitor across the VIN pins to stabilize the voltage? If so, which one?
I'm using a Raspberry Pi 3 Model B with 7" LCD Touch screen and Mini USB Wireless Keyboard

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scruss
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 2:37 pm

What's the no-load output of the 5 V line? Looks like you can adjust it, and ISTR the Adafruit and official PSUs put out 5¼ V.
How long/thick is the power cable to your Raspberry Pi from the PSU? That might be causing your voltage drop.
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Brandon92
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 3:05 pm

And are your sure that your total load is less than the maximal current that the power supply can deliver. Because, when the power supply has a over current. It will limit the current and will cause the voltage to drop.

R-A
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 3:47 pm

scruss wrote:
Sun Sep 16, 2018 2:37 pm
What's the no-load output of the 5 V line? Looks like you can adjust it, and ISTR the Adafruit and official PSUs put out 5¼ V.
How long/thick is the power cable to your Raspberry Pi from the PSU? That might be causing your voltage drop.
I have tried various values. Right now it's resting at 5.78V, open circuit.
I used 26AWG UL1007 DUPONT wires, which should / can handle 4A according to the datasheet: http://www.farnell.com/datasheets/1855471.pdf
I'm using a Raspberry Pi 3 Model B with 7" LCD Touch screen and Mini USB Wireless Keyboard

R-A
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 3:51 pm

Brandon92 wrote:
Sun Sep 16, 2018 3:05 pm
And are your sure that your total load is less than the maximal current that the power supply can deliver. Because, when the power supply has a over current. It will limit the current and will cause the voltage to drop.
I only have the Raspberry Pi 3+ Model B connected, which then connects to an HDMI monitor. The inverter, DS18B20 and current sensors aren't connected at this stage.
I'm using a Raspberry Pi 3 Model B with 7" LCD Touch screen and Mini USB Wireless Keyboard

Brandon92
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 4:46 pm

Maybe you problem is in you cable.
When I use a calculation tool for the voltage drop, you will lose around 412mV. If your total wire is 0.5m at 5V and 3A.

edit
I think this is also confirms by the offical power supply for the Rpi. It used a 18AWG cable, and yours is 26AWG (what is smaller).

R-A
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Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 5:39 pm

Brandon92 wrote:
Sun Sep 16, 2018 4:46 pm
Maybe you problem is in you cable.
When I use a calculation tool for the voltage drop, you will lose around 412mV. If your total wire is 0.5m at 5V and 3A.

edit
I think this is also confirms by the offical power supply for the Rpi. It used a 18AWG cable, and yours is 26AWG (what is smaller).
If what you say is true, then at 5.7V, with 412mV drop, there should still be 5.298V for the Pi. But I often see it dropping below 4.7V, that's a whole 1V drop.

The cable is only 20cm, by the way,which should equate to 160mV drop.
But I will get some 18AWG cable and see.

As I said, this cable is good for 4A, according to the manufacturer's spec.
I'm using a Raspberry Pi 3 Model B with 7" LCD Touch screen and Mini USB Wireless Keyboard

Brandon92
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Location: Netherlands

Re: unstable power with Meanwell DINrail power supply

Sun Sep 16, 2018 6:15 pm

Yes, the cable is rated at maximum 4A. But, this cable has also a resistance of 41R a 304.8 meter. And because you are using a low voltage the resistance is also imported. And I assume that you solder the wires under the usb connector.

Is your power supply good, because it should not deliver 5.7V at his output. Do you have a other load to test the power supply? And is you battery in you multimeter not empty?

edit
Acording to the test rapport the 5.7V is within his spec.

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