External Power Problem

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great forum  - read - all.
i have issue external power following set up:
uno r3
sim900 shield
tft screen touch shield v2.0b
it's phone , works fine when usb connected uno.

will not work external power connected 2.5mm plug.
i have tried can think of:
1. 9v battery
2. 9v mains adaptor
3. 12 v mains - uno gets warm
4. 5v regulated above
5. 3.7v 2000mah battery direct - brand new charged - giving 4.56v checked

what happens is:
1. uno fires up
2. sim900 fires up
3. screen fires 'dimmer' usb powered
4. when sim900 gets connection phone network - screen reboots

it there not enough power amps getting through - hence dim screen when external power connected.
i have tried several unos , same result.

being phone need battery supply of sort connected either 2.5mm conn or vin/gnd.

any suggestions welcome.
thanks


the plug in power feeds regulator give 5v. if put in less 7v, regulator not have enough "overhead" (voltage above output voltage) cannot output correct voltage.

the 9v battery may not have been able supply current required.

are absolutely sure have correct polarity?

weedpharma


Arduino Forum > Using Arduino > Motors, Mechanics, and Power (Moderator: fabioc84) > External Power Problem


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