# Input current VS appliance rated current

Discussion in 'The Projects Forum' started by sangpo, Aug 21, 2013.

1. ### sangpo Thread Starter Member

Aug 17, 2013
74
1
Dear sirs and madams.

I am new to electronic subject. I have a power adaptor wich is rated 210-230 Ac voltage (input) and 7 dc voltage and 500mA.(out put)

I have an electronic device which is rated as 7 dc volt and 200mA.

Can I connect my electronic device to this power adopter safely? If Yes then how? If the ans is No, then How?

Please kindly share your knowledge, since Im interested in leaning concept of electronic. Thank you

Sangpo

Jul 18, 2013
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3. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,769
969
The answer is yes..
The questions you ask yourself to determine the answer is...

Is the voltage of the power supply equal the voltage of the load?.. yes
Is the current rating of the power supply greater than the load needs?..yes

If either of the answers to those 2 questions is no then it won't work.

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4. ### BillB3857 Senior Member

Feb 28, 2009
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Even though the current available from the supply is greater than what your device needs, the above response applies, maybe. If the supply is a regulated supply, no problem. If on the other hand, it is designed to provide 7 volts at the rated load, a lighter load may result in higher output voltage. The only way to know for sure is to measure the output voltage with no load on it. Also, the polarity of voltage at the connector should be verified before connecting to a device it was not specifically designed for.

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5. ### sangpo Thread Starter Member

Aug 17, 2013
74
1
Okey Thank you, mcgyvr

With regards to OUTPUT current of power supply (500mA) Vs rated current of a devise,(200mA) Doesn't it mean that 500mA will flow to load (devise) and burnt the load/devise whose rated current(200mA) is lower than that of supply)?

thank you

6. ### bertus Administrator

Apr 5, 2008
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2,344
Hello,

When the voltage of the powersupply is correct, the device will only take the current it needs.
If you powersupply can give 500 mA and the device needs 200 mA, 200 mA will be taken from the powersupply.

Bertus

7. ### sangpo Thread Starter Member

Aug 17, 2013
74
1
OK Bertus, Thank u for your prompt response. I understood that now clearly.
But, suppose if the SUPPLY Volt is 9VDC instead of 7 volt( rest remained same), then will the load/device be damaged? Please kindly clear my doubts. Please dont get irritated with such kind of questions. This is only forum from where I can Learn electronic)because no institution for learning electronic in my country.

Thank u
sangpo

8. ### bertus Administrator

Apr 5, 2008
15,645
2,344
Hello,

When you apply 9 Volts to a device that is designed for 7 Volts, the following things might happen:
1) the device has a great marge in the supply range and will work properly.
(this could happen when there is an internal voltage regulator).
2) the device has a strict supply range, the device will probably burn due to over voltage / over current.

Bertus

9. ### sangpo Thread Starter Member

Aug 17, 2013
74
1
THanks Bertus.