# 3.7v DC to 220v AC inverter

Discussion in 'The Projects Forum' started by Jamie097, Jul 23, 2018.

1. ### Jamie097 Thread Starter New Member

Jul 23, 2018
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I’m very I’m experienced and attempting to create an inverter to run 50 cm2 of EL tape with a rechargeable 500 mA lipo battery, both of which come from Adafruit. I’m aware that they sell inverters for their EL products, but I’m really wanting to make something small enough that I can hide it in a helmet I am building, and I feel like their inverters are too big for the job. There are basic inverter videos I’ve seen with a transformer and transistor, but I’m not sure where to go from there.

Nov 13, 2015
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3. ### Jamie097 Thread Starter New Member

Jul 23, 2018
4
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How would I go about splitting the load on these devices. I’m very inexperienced

4. ### Papabravo Expert

Feb 24, 2006
11,993
2,574
Just because you can do something doesn't mean it is a good idea. You need to familiarize yourself with the immutable law of power conversion. In short: power output of a converter will always be less than the power input -- sometimes it will be much less.

An example might be instructive:
Suppose we want to supply 220 VAC @ 100 milliamperes. The product of those two numbers is the required output power. It is 22 watts.
Next we assume an efficiency factor for the conversion. Let's call it 80%. That means the input power required will be 22 / 0.8 = 27.5 Watts
To get 27.5 Watts out of a 3.7 VDC battery will require 27.5 /3.7 ≈ 7.5 Amperes

This is a very high discharge rate and will likely drain most batteries in a matter of minutes.

To make a converter with an efficiency of greater than 80% becomes incredibly difficult the closer you get to 100%.
Do you have the resources to engage in such an effort?
Do you know anybody who does?
Are you sure this idea is practical?​

5. ### Ylli Active Member

Nov 13, 2015
509
134
I could be wrong, bit I don't think 50cm² of EL tape will draw anywhere near 100 mA.

6. ### Jamie097 Thread Starter New Member

Jul 23, 2018
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The information on their website says .14 mA/hr for 1 cm2

7. ### Papabravo Expert

Feb 24, 2006
11,993
2,574
mA/hr is NOT a unit of current consumption. Let us start with how much current you actually expect to draw from this inverter.

Alternatively: how many cm2 units of area do you have. Why all the misdirection - why can't you quote an actual current?

8. ### Jamie097 Thread Starter New Member

Jul 23, 2018
4
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• Size: 100 cm x 1.5 cm about 1mm thick. The glowing part is 1cm wide.