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Author Topic: Nanode5 - Sketch works on FTDI Power, not on External DC  (Read 560 times)
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This relates to Nanode 5 with winode backpack. Hoping I can get an answer from this Forum as very little response comes from the Nanode community it seems. May have backed wrong horse going with Nanode?

I'm revisiting a working installation that stopped working last Autumn. Have gone back to basics and realise how much I've forgotten in the year since I built and programmed the project. Hope these aren't dumb questions therefore.

I'm using a simple fade sketch to test output of Pin5 (an LED) and associated PWM circuit. Sketch works perfectly on FTDI powered set up but,with FTDI removed and replaced with a 9v DC supply on the screw terminals, Pin 5 LED comes on at full brightness and stays on.

Pressing reset does one of following, seemingly at random:-
a) Pin 5 LED glows at one intensity
b) Winode LED (pin 6) lights
c) Pin 5 LED flashes rapidly then stays lit, along with Winode LED
d) Pin 5 LED flashes rapidly then stays lit, without Winode LED
e) Pin 5 LED flashes once and all LEDs stay off.

Please can someone explain what is going on / what am I missing?

Further info and Q's after a bit more experimenting:-

I've tried uploading the original project sketch which works fine when powered from FTDI.
Changing over to 9vDC through the screw terminals the same sketch appears to work for several minutes before it hangs.

Can I use the FTDI/USB cable for the Serial Monitor function whilst powering from 9vDC through terminal block or will I fry the FTDI board? This might indicate where/why sketch hangs.

My reasoning for going with the higher voltage is that USB power will give less voltage on the (PWM) outputs than if I power from 9v. I'm feeding output to 0-5v controller but getting max 2.8v from Nanode when powered by FTDI. Hoping 9v supply will give higher output.

Thanks
« Last Edit: January 28, 2013, 06:43:49 am by DickiePhitt » Logged

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You should be getting 5V on the 5V rail regardless of which voltage input you use.  The FTDI cable should supply 5V directly and the DC_IN connector should go through the on-board 5V regulator.  If your 5V line is at 2.8V it may be because something is drawing more current than it should.

Measure the voltage between Ground and the Vcc (5V) pin with the two supplies and report back.
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On FTDI power I'm getting 4.6v, on 10v DC external 4.9v on the 5V rail/output.

Been over boards cleaning soldered joints but still same issue - sketches runs continuously on FTDI but hang after a few minutes on external power.

Using "digitalWrite(5, HIGH);" to switch the (normally) PWM pin on all the time still gives 2.8V when 5V rail is showing 4.6V

Any suggestions (a) why voltage difference and (b) why external power should be causing sketches to hang?

Also, can I use FTDI at same time as external DC to monitor serial?

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How current are you drawing?  You might be overheating the onboard regulator.
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Using "digitalWrite(5, HIGH);" to switch the (normally) PWM pin on all the time still gives 2.8V when 5V rail is showing 4.6V

Any suggestions (a) why voltage difference and (b) why external power should be causing sketches to hang?

Three reasons I can think of for a low voltage on an output pin:

1) The pin is set as INPUT and writing HIGH is just enabling the internal pull-up.

2) There is a heavy current draw on that pin. More than the 40 mA Absolute Maximum.

3) The ATmega is damaged.
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Went through your suggestions.

I knew Pin definitely set to output in sketch "pinMode(5, OUTPUT);"

Substituted another ATmega but problem persisted.

Disconnected pin5 output wire - GOT LINE VOLTAGE !

Reg now running at a temp where I can (just) grip it.

Many thanks for pointing me to where problem lay.

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