# 3.7v DC to AC inverter

Discussion in 'The Projects Forum' started by chinesethunda, Nov 8, 2013.

1. ### chinesethunda Thread Starter New Member

Nov 8, 2013
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So I am trying to build an inverter to power an electroluminescent panel and I want to build an inverter to power said panel. most of the inverters use 12v inputs and I would like to build a custom inverter using this battery to power this EL panel, what kind of parts would I need to build the inverter to power this panel?

2. ### Papabravo Expert

Feb 24, 2006
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Back of the envelope calculations:

10 cm x 10 cm = 100 cm^2
Current consumption is .14 mA/Cm^2 * 100 Cm^2 = 14 mA
Power Required from Inverter is 14 mA * 110 VAC = 1.54 Watts

Assuming an efficiency in the inverter of say 80% requires the battery to deliver
1.54 / .8 = 1.925 Watts which we can round up to 2 Watts.
2 Watts at 3.7 V = 540 mA
2 Watts at 3.0 V ≈ 670 mA

Q: How fast will that level of current consumption drain the battery?
A: 1.5 to 2 Hrs

3. ### chinesethunda Thread Starter New Member

Nov 8, 2013
11
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so it would last about 1.296 hours. given this information, I was thinking about cutting the panel and making it smaller, allowing the battery to last longer. But my problem remains how would I create an inverter to power this panel?

One possibility I was thinking was to use a resonant circuit since I know that the panel has a capacitance of 45nF. I have yet to measure what the parasitic resistance of the panel, but I don't know how to create an inverter.

4. ### Papabravo Expert

Feb 24, 2006
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Well the block diagram might have a 400 Hz. sinewave oscillator, a transformer, and a power amplifier. That should get you started.

5. ### Alec_t AAC Fanatic!

Sep 17, 2013
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How about using a boost-converter IC?

Sep 9, 2010
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Feb 24, 2006
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8. ### wayneh Expert

Sep 9, 2010
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Fair enough, if that's the goal. I just find that a lot of folks post here unaware that cheap commercial products are already available. I saw enough reinventing of the wheel in my professional career that I'm overly sensitive to it.

One thing the OP will learn is that EL inverters run in the 1-2kHz range.

9. ### chinesethunda Thread Starter New Member

Nov 8, 2013
11
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where might I find such an oscillator? I was aware that the panel would require around 110VAC and run at 1-2kHz. I am not too familiar with how I would use the transformer for the inverter. if anyone can clear that up for me a little that would be much appreciated.

10. ### wayneh Expert

Sep 9, 2010
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The transformer would be used to step up the voltage. A typical "wall wart" power supply uses a transformer to step voltage down from 120V to 12V, for instance. You would do just the opposite to convert 12V oscillations to 120V.

Look for oscillator circuits based on the popular 555 timer IC. You will find many EL inverter circuits based on that.

11. ### Papabravo Expert

Feb 24, 2006
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The specific datasheet mentions 400 Hz., but I don't think there is anything magic about that frequency. A higher frequency could mean smaller components.

A 555 produces a square wave. I was thinking that a Wein Bridge oscillator might be a better fit for this application.

12. ### ifedee New Member

Nov 10, 2013
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The part of assuming an efficiency in the inverter of say 80%, is it not supposed to be calculated as
1.54 *.8 = 1.232 Watts ?

13. ### Papabravo Expert

Feb 24, 2006
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I don't think so. The idea is that the power out must be less than the power in. If the power out is 1.54 Watts, then you divide by the efficiency to get the power in. To check your calculation you multiply the power in by the efficiency to get the power out. BTW discussion of overunity, where power out is greater than power in, is most definitely not allowed on this forum.

14. ### ifedee New Member

Nov 10, 2013
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how was the level of current consumption drain for the battery calculated as
1.5 to 2 Hrs?

15. ### Papabravo Expert

Feb 24, 2006
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The capacity of the battery is listed as 1000 mAh (milliamp-hours). So any combination of of current flow and time multiplied together should yield 1000.

16. ### ifedee New Member

Nov 10, 2013
5
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why do we have to calculate for 2watts at 3.0V since the battery has a nominal voltage of 3.7V

17. ### Papabravo Expert

Feb 24, 2006
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Because as the battery discharges, the voltage will drop. When it gets to about 3.0V it will very soon drop toward zero and need recharging. Google "Battery discharge characteristics".

18. ### ifedee New Member

Nov 10, 2013
5
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thanks @ papabravo

please does anyone have an idea on how to build a resonant circuit inverter to output 3.7V?

19. ### Papabravo Expert

Feb 24, 2006
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I'm not sure what you are asking here.
An Inverter has a DC input and produces an AC output.
A DC-DC converter has a DC input and a DC output.

In either case the power out will ALWAYS be less than the power in.

20. ### ifedee New Member

Nov 10, 2013
5
0
please does anyone have an idea on how to build a resonant circuit inverter with 3.7V input rather?