# Quick question

Discussion in 'General Electronics Chat' started by Redscarf, Sep 1, 2015.

1. ### Redscarf Thread Starter New Member

Jan 28, 2015
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0
Hey guys, i was just wondering if I had a 8.45V power source that provides about 90mA what would you recommend as the best way to get the current up to at least 550mA? Thanks in advance!

2. ### dl324 Distinguished Member

Mar 30, 2015
3,379
651
Assuming you want 8.45V out, you need a different power source.

3. ### djsfantasi AAC Fanatic!

Apr 11, 2010
2,905
879
1) AC or DC? If the former, get a 6.1:1 transformer and you'll get about 1.4 V at approximately 550mA. If you need 8.45V, then you can't do it with just what you have,

2) Get a more powerful power source.

4. ### Redscarf Thread Starter New Member

Jan 28, 2015
19
0
DC, but all right that's all I guess.

5. ### Redscarf Thread Starter New Member

Jan 28, 2015
19
0
Oh what if I use a transistor

6. ### dl324 Distinguished Member

Mar 30, 2015
3,379
651
At 100% efficiency, power in = power out. Your power source, in round numbers, is 0.85W. At 500mA, you could get a volt or so...

Jan 28, 2015
19
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Oh I see

8. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,791
976
You just need to know the math to understand what you can/can't get..

Volts x Amps = Watts
so
8.5V x .09A = .765watts of power available

Now Watts / Amps = Volts
so
.765w/.55a=1.4V

So assuming 100% efficiency (and you won't get that in the real world) as stated above you could supply 550mA BUT that would only be at 1.4V

This chart shows you all the ways to use volts/amps/resistance/wattage to figure out each other.
http://www.ohmslawcalculator.com/ohms-law-wheel