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EL Wire Inverter powered with no load?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

EL Wire Inverter powered with no load?

by DeathBloom on Thu Nov 07, 2019 1:43 pm

Hi, community!

I've read a lot of things around EL wire and how to control it, but there's one question which bothers me and I can't find an answer to it. I hope it will be answered here.

On Adafruit and other resources it is stated: Do not power up voltage inverter without a load as it will damage it.

However, lots of projects need an el wire to blink. In order to do so we can use El Escudo or similarly built schemas. E.g. I've created a scheme like this, with similar components used in El Escudo:

https://i.stack.imgur.com/yqR2m.png

I am successfully able to blink the El Wire with the code, which opens and closes the triac gate every 3 seconds.

Finally, here's the question: Does it mean, that every 3 seconds my Voltage Inverter is powered with no load, since, technically, it looks like the el wire is not connected while this 3 seconds. I can also hear the high-pitched sound from my inverter when the El wire is not lit. Will the inverted be damaged?
If the above is right, can the issue be work arounded by adding a capacitor? Or I shouldn't worry about it at all?

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by adafruit_support_bill on Thu Nov 07, 2019 2:08 pm

Does it mean, that every 3 seconds my Voltage Inverter is powered with no load, since, technically, it looks like the el wire is not connected while this 3 seconds.

That is correct. Operating without a load is stressful to the output transistors and can cause premature failure of the inverter.

The El Escudo is a multi-channel board. I'm not sure about the current documentation for the board, but they used to suggest adding capacitor as a dummy load to one of the channels, so you could always have some load on the inverter.

Obviously, that requires some discipline in your code to make sure that at least one channel is always active.

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Re: EL Wire Inverter powered with no load?

by DeathBloom on Thu Nov 07, 2019 4:16 pm

Hi, Bill!

Thank you for the prompt reply!
That what I thought.

Few more questions arose:
- what if I add a minimal load capacitor along side with the el wire which works permanently. So it drains some power from inverter while no El Wires are off and is still active when some or all of them are on. So it shouldn't be too demanding to not steal the power needed for wires. This will save a lot of efforts in code, because I won't need to code that case when no el wires are on.
- what should be that capacitor? I suppose that at least it should be 200v tolerant, however, not sure what should be the capacitance
If I refer to this page:
https://learn.adafruit.com/el-wire/using-el-wire
the EL Wire Modeling section tells, that 6nF capacitor + 100KOhm resistor connected in parallel are something like one meter of the wire. I have a feeling like I may need an equivalent of 25cm for my needs. Does it mean 1.5nF capacitor and 400KOhm resistor? Or maybe resistor is not needed at all since we are not going to perfectly model the wire and just drain some current from Inverter?

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by adafruit_support_bill on Thu Nov 07, 2019 4:59 pm

Wiring the dummy load directly across the output of the inverter (before the Triac) will keep things simpler. But it will give you a slight decrease in overall brightness in your EL.

The dummy load should approximate the minimum recommended load for your inverter. So if that is 25cm of wire, your estimate is correct. Some sources recommend a resistor/capacitor combination. Others just call for the capacitor. I've done a couple of projects with just a cap for a dummy load without problems.

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Re: EL Wire Inverter powered with no load?

by DeathBloom on Fri Nov 08, 2019 9:53 am

Thank you very much!

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by DeathBloom on Fri Nov 08, 2019 10:20 am

By the way, I see, that on the schema the capacitor with polarity is depicted. However, do I really need a polar capacitor here? The AC nature of inverter tells me that the capacitor should be non-polar. Is this correct? I've also did a brief search for capacitors and it looks like most of those which are hundreds volts tolerant and around 1.5 nF are the non-polar ceramic ones, like this:
https://static.chipdip.ru/lib/250/DOC000250692.pdf

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by adafruit_support_bill on Fri Nov 08, 2019 11:03 am

You are correct. It is AC, so you want a non-polarized cap. Most available choices in that voltage and capacitance range will be ceramics.

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Re: EL Wire Inverter powered with no load?

by DeathBloom on Sat Nov 09, 2019 8:20 am

Thanks, Bill! That was a great help!

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by DeathBloom on Sun Nov 24, 2019 10:19 am

Dear Bill et al,

I've just bought this capacitor:

https://static.chipdip.ru/lib/961/DOC002961542.pdf

In the datasheet it says DC everywhere. Does it mean I can't use it for my purposes in AC environment?

DeathBloom
 
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Re: EL Wire Inverter powered with no load?

by adafruit_support_bill on Sun Nov 24, 2019 10:56 am

Polyester capacitors are non-polarized, so they are suitable for use in AC applications.

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Re: EL Wire Inverter powered with no load?

by DeathBloom on Sun Nov 24, 2019 1:15 pm

Great to hear that! Thank you very much!

DeathBloom
 
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Please be positive and constructive with your questions and comments.