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Topic: Solar Cell Preamplifier Design Problem

Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000

posted 12-01-2005 07:20 PM

Marin, as I said before AND you seemed to poo-poo and ignore... I ***STILL*** recommend to quit F*CKING around with the so-call "experts" and look at the FT manual section. Specifically the SMART manuals.

They have manuals that include schematics that are not only cleaver and efficient, but also follow good engineering practices and use the "proper" parts and component values. Some really good stuff. Oscar and his team REALLY knew their stuff!

OBTW: Scrap the photo diode and use a cell as others have suggested.

AGAIN! Good Luck!

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-02-2005 03:31 AM

Yes, planing to go with cell, but here stereo solar cell with bracket cost $300, so isn't so cheap for experiments.

I look at manual section and smart only got schematic at old stuff, not on newer.

But i'm think i'm on wright way to get some good preamp.

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000

posted 12-02-2005 03:49 AM

Holy Smokes! $300 for the cell and mount? What projector are you building this for?

Smart may have newer stuff listed on their website in the manual section. BUT! There is nothing wrong with their older stuff... I think they made a mono optical preamp, now discontinued, that was very simple and reliable.

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-02-2005 06:13 PM

OK, it's 255$ [Razz]

It's for prexer or Iskra (ernemann 7, 8) but price is same.

Gonna look manuals!

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-07-2005 07:28 AM

I try some kinds of other designs and solar cells in sound head but still i need decoupling capacitor at cell input.

Can be this does without it? And how decoupling capacitor effect on signal and frequency response?

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Robert Minichino
Master Film Handler

Posts: 350
From: Haskell, NJ, USA
Registered: Dec 2005

posted 12-07-2005 07:43 AM

Since there is a DC offset on the solar cell output you will need some way of eliminating this; a DC-blocking capacitor is the easiest way. If it's appropriately sized it will roll off only very low frequencies (below, say, 20 Hz) and have no audible effect. I'd use a bipolar electrolytic bypassed (in parallel with) with a small-value (0.1uF) mylar or polypropylene cap.

An alternative is to use a DC servo. This is an amplifier with a low-pass on its input, and you mix its output in with your signal to zero-out the DC offset in the signal. This way the signal never passes through a capacitor, but it's too complex in my opinion.

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-07-2005 10:16 AM

quote: Robert Minichino
I'd use a bipolar electrolytic bypassed (in parallel with) with a small-value (0.1uF) mylar or polypropylene cap

Robert,

can you tell what is that bipolar cap. you use in paralell with this of 0,1uF?

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Robert Minichino
Master Film Handler

Posts: 350
From: Haskell, NJ, USA
Registered: Dec 2005

posted 12-07-2005 11:12 AM

A bipolar electrolytic capacitor is like having two electrolytic capacitors connected back-to-back in series; these are often used in speaker crossovers.

I don't think you really need one, though. A regular polarized electrolytic capacitor should be fine in this application as the cell works like a diode anyway. Sorry for any confusion.

A small value high-quality capacitor in parallel with a large electrolytic won't change the total value much, but it will mean that any high-frequency signals that the electrolytic might not pass well (due to internal inductance, for example) will pass through the small film capacitor instead.

You probably don't even need the film bypass capacitor as most electrolytics should be fine in the audible frequency range, but I have a big box of them so I don't mind adding the parts for my own circuits.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-07-2005 05:38 PM

quote: Phil Hill
Marin, as I said before AND you seemed to poo-poo and ignore... I ***STILL*** recommend to quit F*CKING around with the so-call "experts" and look at the FT manual section. Specifically the SMART manuals.

Marin,

It is sad that there are people here that seemingly want to discourage you from the learing process ***AND*** bettering yourself. One learns absolutely nothing by simply copying an existing design, and some of those designs are ***VERY*** inferior to what you could build yourself. I personally encourage you to proceed down the road you were on and learn all that you can on your own [thumbsup]

It'll make you a much stonger, more valualable person in the long run.

For more help down ***Your*** road I reccomend the DIY AUDIO WEB SITE . There are ***ALOT*** of very gracious, friendly people, and many degreed electrical engineers that would be glad to help you out.

Mark

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-08-2005 05:35 AM

quote: Mark Gulbrandsen
It is sad that there are people here that seemingly want to discourage you from the learing process ***AND*** bettering yourself.

Thanks for this Mark!!!

Yes i know for DIY Audio and i'm already there!

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-08-2005 05:52 AM

I don't think anyone is actually putting anyone down
But I think Phils advice is very valid of dropping the photodiode and using a solar cell
Also there is little point ion reengineering the preamp design as most of it has been researched to death
There are some nice prepackaged mic preamp chips (I believe in the SSM line) that work very well

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-08-2005 10:53 AM

quote:
I think Phils advice is very valid of dropping the photo diode and using a solar cell

Hmm $255 for cell with bracket i think is expensive!

Also could somebody described difference between solar cell and photo diode?

I know guy whose working also what I'm doing, and he told me that he didn't noticed any difference between solar cells and photo diode, he install CP200 and try to put photo diode and solar cell for comparing and say that didn't get any difference.

What you think?

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Richard Fowler
Film God

Posts: 2392
From: Ft. Lauderdale, FL, USA
Registered: Jun 2001

posted 12-08-2005 11:24 AM

Raw stereo cells are $30 to $80.00 depending on type....machine or modify your bracket [Wink]

I noticed Eastern European and Russian machines favor photo diode set ups.

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000

posted 12-09-2005 12:39 AM

Oh Mark! You're such a brute. [Wink]

I never said what YOU said I did! Get off the I-30 stuff! You REALLY need to go back to reading comprehension 101 before you yap as some holy know-it-all.

As usual, you spout off before reading and comprehending what was/has been said. Perhaps you should hold your comments until YOU read ALL the previous comments in the thread.

Go back and re-read this thread. I only ***suggested*** that Marin LOOK at those schematics for ***IDEAS***. I NEVER said to COPY the circuits. JFC!

BTW Mark: Many others, including myself have posted several times here about improving his design considerations. It really gets ***F*CKING*** annoying that HE keeps asking the **same** question over and over again EVEN after HIS questions have been answered by many including myself. It appears that HE is not taking the advice of the FT members or is just DENSE.

Mark, get off your high-horse. It's an insult to MANY FT members that YOU think there are BETTER "qualified" people (electrical engineers, techs, etc) elsewhere just points to insulting the talent here.

quote: Marin Zorica
quote=Gordon McLeod
"I think Phils advice is very valid of dropping the photo diode and using a solar cell"

Hmm $255 for cell with bracket i think is expensive!

Marin, perhaps YOU should take up another HOBBY!

OBTW Marin: I have NO idea as to what that cell assembly costs and was just amazed at what you said. BUT! You apparently took my inquire wrong.

Re Marks post:

quote: Kiss Kiss Marin Zorica
Thanks for this Mark!!!

Just like Mark, Marin YOU NEED to read ALL of this thread...especially before you stick your nose up his butt!

I was only asking about what projector since I had a spare SIMPLEX cell I would be willing to send you free.

Perhaps Mark in his limitless experience, knowledge, ignorance, usual arrogance, and vast stock of parts would be willing to send you one free to help you out? If not, I still offer my Simplex cell. NO Charge.

[ 12-09-2005, 03:17 AM: Message edited by: Phil Hill ]

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-09-2005 07:00 AM

First of all we ***MUST*** stop with all this hard words!!

Phill, don't mean to upset you, i know why you advice me for using solar cell, and if you have one for give me I'll be glad to get it from you, also i was little bit more for photo diodes, because they are cheaper and you may get it everywhere, and like Richard said in Eastern European projectors there are mostly used photo diodes, and here i servicing that machines, because there are plenty of them.

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