In the circuit(it's a Ni-Cd solar charger) below i require a 100uH aircore inductor. Is it ok if I use a readymade inductor(which is not an aircore inductor). Will it affect the circuit in anyway?

Also I did not get a 1N5117 zener diode(it's 400V) why do i require such a high capacity diode for just a 6V application? I got 2, 200V zener diodes. Is it ok if I use them?

Another thing is that the MAX639 IC costed me a whooping 8 US dollars! Why the hell is it so costly??? My allowance(monthly) is only 12dollars(US)!!!

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solar1.gif (9.0 KB, 509 views)

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U.S.S.R.

 

Regarding the inductor - if the function of the inductor were to prevent the flow of AC then it would seem that the inductor design would not be especially critical. If the inductor's function were to store then return the power to the circuit then you'd want to be sure that the core was such that efficient operation would result.

Background - in any inductor, when presented with alternating or varying current, a magentic field builds then collapses. The core material allows an inductor to be smaller (when compared to an air coil). Some cores soak up the collapsing field (resulting in heating) while others do not.

This represents my understanding - corrections/additions are welcome. It isn't the whole answer but if someone could describe the function of the inductor we'd be moving in the right direction.

Regarding the cost - they got it, you want it - supply and demand my friend.

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stevez

 

Zener Diode? No, that should be a schottky rectifier.. It is necessary for this application because of the voltages generated from the coil.

Also, wayy off the the inductor. Do not use an aircoil inductor for this! The inductor needs to be able to take the currents in generated in your circuit. Also, it needs to be a high-Q inductor, which has a low series resistance at 100mH. Use any available that has reasonable quality and can take around 0.5A should be fine.

Steve

 

I also don't understand fully, but this sematic a crop of original datasheet, and contain really 400V zener diode...

 

No, this schematic isn't from the datasheet whatsoever, it was designed by some other person. All I know is that in the datasheet, there is no mention of using zener diodes.. There is a mention of using schottky rectifiers in order to switch the coil, but I can't see how one could use the zener diode in this circuit..

Also, in the datasheet, it mentions not to use aircoil inductors because of their low current capabilities.. It recommends using smaller coils with the proper ratings for the application.

This is why I follow datasheets when designing.. not other people's schematics. I trust the manufacturer more then anyone else..

Steve

 

I suspect that the 1N5117 zener is used more for the switching speed than anything else and that the designer used what he had.

Maxim use 1N5817 schottky.

Looks strange.

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All i\'s dotted & all t\'s crossed.

 

Schottky diodes switch much faster then zeners can? Am I wrong?

Steve

 

Here is the original datasheet on MAX639 describing exactly the same circuit as the one I posted. It too shows 1N5117 zener diodes. Again, can I use a 200V zener instead of a 400V without affecting the function of the circuit much???

http://pdfserv.maxim-ic.com/arpdf/AppNotes/A0809.pdf

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U.S.S.R.

 

Oh, alright..

Yes. You can use two zener diodes in series to obtain your needed 400V, it just adds....

Steve

 

But in this case the forward voltage drop double.

 

..

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U.S.S.R.

 

I am confused...

Steve

 

1. I replaced the 1N5117(400V) zener with 200V zeners.
2. I used a 100uH bead type inductor.

So, what output should I read? How many volts??? How do I know the circuit is working correctly???

Incase you are wondering which circuit I am talking about. I am attaching it.

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solar1_180.gif (9.0 KB, 422 views)

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U.S.S.R.

 

Hey,,

Can the bead type inductor take the current?

Steve

 

Yep, it can take the current.

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U.S.S.R.