RADDS LCD Display Flickering & Dimming When Extruding?

I have some real issues with the RADDS LCD.

When I have just the Arduino powered it's very dim, and I have to turn up the contrast, but then when I power on the PSU too, it become much brighter and I have to turn down the contrast and it flickers.

Then when I print, every-time the extruder motor is running the LCD get much dimmer while extruding or retracting????.

I don't think its sag from the USB cable or supply, as I have tried 5 USB cable, half a dozen different USB sockets on multiple machines, a DC power supply, and a mini USB 2Amp wall PSU for the Raspberry Pi.

... it's the voltage level, what's changing with load - add an extra PS for the 5V-support ...

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Viktor
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Quote
VDX
... it's the voltage level, what's changing with load - add an extra PS for the 5V-support ...

Thanks Viktor, do you mean add a power supply to the Due via the barrel socket power as well as the USB connection? (and if so is 9v OK?)

Edited 1 time(s). Last edit at 02/10/2016 12:33PM by peps1.

... the USB-connector can only handle 5V! - it's direct connected to the 5V-circuitry, so higher voltages will damage some of the chips.

Iit seems, your 12V PSU is not strong enough to drive the motors and support the 5V regulator with enough current for the display too.

So better search a 12V PSU with more current ...

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Viktor
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Quote
VDX
... the USB-connector can only handle 5V! - it's direct connected to the 5V-circuitry, so higher voltages will damage some of the chips.

Yes, I understand the USB is 5V and the Due runs on 3.3V, I was wondering if you were suggesting ALSO powering it from the 2.1mm jack that will take 7-12V power supply.

Quote
VDX
Iit seems, your 12V PSU is not strong enough to drive the motors and support the 5V regulator with enough current for the display too.

So better search a 12V PSU with more current ...

Its a 20A 12V PSU, dose that sound to weak for a i3 style printer running 5 x 1.3A motors?

... the 20A should be enough, so maybe you have another issue - maybe a faulty part, drawing too much current, so the 5V for the LCD breaks down?

Can you measure the voltage level of the 5V while printing?

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Viktor
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Sure,

Is it OK to read the voltages from the Aux1 pads, as they look like they are going to be the easiest to get to?

yes, it's OK

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Viktor
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OK here are the quite worrying voltage reading from the 5V pad.....

Just USB power to the Due = 4.53V
USB + 12V PSU = 7.15V

Heating Bed = ~6.7V
Heating Bed + Hotend = ~6.4V

Printing= ~5,8V

And here is how I have my printer setup:

Switched out the Due for another one, and now get 4.61V under USB, and a much more respectable 5.08V when powered by the printers PSU.

As expected this also resolves the flicking on the LED, and having to adjust the contrast when powering over USB vs PSU.

Will double check the voltage stays stable when printing, just in case!

... seems, the 5V-voltage regulator on the old Due is broken

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Viktor
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Yes, with a new Due, everything seems be be behaving as it should

Thank you for your help