Film-Tech Forum ARCHIVE: Solar cell pre-amplifier

This is topic Solar cell pre-amplifier in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Bruce McNaughton (Member # 2691) on 07-18-2011, 03:17 AM:

Does anyone have a circuit diagram for a mono or stereo pre-amplifier for use with a solar cell. I know these are quite simple circuits.

I can be contacted at bruce@arandafilm.com.au

Thanks

Bruce

Posted by Chris Slycord (Member # 4239) on 07-18-2011, 06:59 AM:

Clicking on your name already shows your email in your account info... and it's against the rules to put your email in the body of a post...

Posted by Robert Minichino (Member # 3495) on 07-18-2011, 10:49 AM:

The front end is going to look a lot like a balanced mic preamp, but with a slit-loss compensation circuit, and for mono, a low-pass filter. You can see some schematics in the manuals in the Warehouse section of this site.

Posted by Dave Macaulay (Member # 813) on 07-18-2011, 03:24 PM:

Any mic preamp will work, but you will probably have to attenuate the signal to avoid overloading it. Most line level inputs are not sensitive enough. You also need to load the solar cell with about a 1K resistance. The solar cell is a current source (converts light to amps) and without this load the output is pretty distorted.

Posted by Jeff Taylor (Member # 443) on 07-18-2011, 04:01 PM:

Dave is right on. For a while I used a run-of-the mill (found it in a vacant building) Bogen PA amplifier feeding the cell into one of the mic inputs loaded down with a 600 or so ohm resistor (it's not too critical and a tiny one will do). Sound was just fine. Good luck.

Posted by Marin Zorica (Member # 1716) on 07-18-2011, 04:18 PM:

I have pretty much expiriance on this, as true the years I did made many of my pre-amps for cells. As pointred above cell is current source, and impedance should be minimum to zerro, and with that we have problem of small signal, so common is to have 100ohm resistor in serie with cell which gives same input impendace and if we raise it above this the HF loss will be very noticable. In case using some mic preamp we don't have HF eq, and it would be good to insert transformer between cell and mic input.

And if you want to do something good, but is not so simple, as there are quite few ic's and so, let me know I can share some of my schematic with pcb's.

Posted by Bruce McNaughton (Member # 2691) on 07-18-2011, 06:58 PM:

Thanks to all.

Yes Marin I would very much like to see a circuit so I may build something from scratch. I do not have a microphone pre-amp at hand so I will need to start from the beginning

Regards

Bruce

Posted by Frank Angel (Member # 248) on 07-21-2011, 06:56 PM:

I have quite a few unopened Opamp microphone preamps that I would be happy to send you for the shipping. They are octal base so they just plug into an octal socket; add load resistors, and depending on the rest of your equipment, you can add a trim pot if u like, but pretty much they are totally self-contained -- really sweet package, plus, having used them for quite a number of years for both microphones and solar cell pickups on 16mm and 35mm heads to replace the original photoelectic cells with solid state cells, I can tell you they are very rich and warm sounding with plenty of headroom.

If you would like a couple, just write to me and figure out what the shipping would be from Brooklyn NY and they are yours. You may find it will cost you less to build from scratch, but you are welcome to them if they will save you some time.

Posted by Robert Throop (Member # 61) on 07-22-2011, 09:04 AM:

quote: Frank Angel
but pretty much they are totally self-contained

You do need a power supply.

Posted by Scott Norwood (Member # 30) on 07-22-2011, 09:30 AM:

Go with Frank's generous offer. There is a schematic of how to wire this on the Opamp Labs web site.

Posted by Frank Angel (Member # 248) on 07-22-2011, 04:20 PM:

As Bob says, a power supply needed...that they do.