Solar cell light meter

[oystershred]

Hi guys, anybody tried this?

I had the unfortunate experience of buying a metraphot light meter that had NO selenium cells inside, and the shipping cost is too much such that it would be pointless to send it back for a refund. After leaving rather nasty feedback for the e-bay vendor, I have decided to "make lemonade" out of this and try to use solar cells as a replacement for the selenium light meters.

Components I need (and I may need your advice for this!)

1) Soldering iron to solder the wires of the solar cell to other necessary components (anyone have any to recommend? like how many watts etc)
2) Solar cell (to be disemboweled from a calculator)
3) Variable potentiometer about 100K ohms (anyone know where to get this?)
4) Milliampmeter (Volt meter can't really measure that much

This may or may not take off. I am already finding it difficult to take apart the metraphot. If I do manage to get it taken apart, I will post photos of my progress! wish me luck!
alternatively, if anyone knows of anybody who repairs light meters, PLEASE LET ME KNOW! Steven of camera hospital doesn't do this.

 

[Nikkornos]

Whahh Evil Bay again!

1) Soldering iron to solder the wires of the solar cell to other necessary components (anyone have any to recommend? like how many watts etc)
You can buy a Goot 15 watt soldering iron from Sim Lim Tower (not square). Get some good solder also.
You need a wet pad to clean the tip.

2) Solar cell (to be disemboweled from a calculator)
Or you can buy from Bell electronics at level 4 of Sim Lim Tower.

3) Variable potentiometer about 100K ohms (anyone know where to get this?)
100K ohms has two types, log or linaer. You should buy the small linear type from Bell.

4) Milliampmeter (Volt meter can't really measure that much)
Most of them are rather large .. measuring A. mA or uA meter are hard to find.

What is your line of thought? What model is the light meter? Do you have the circuit diagram?

 

[Nikkornos]

Also, the light intensity vs I curve on the selenium and on the solar cell may be different.

You could be better off to ditch this and get a new meter, like the Sekonic L308.

 

[oystershred]

Also, the light intensity vs I curve on the selenium and on the solar cell may be different.

You could be better off to ditch this and get a new meter, like the Sekonic L308.

Hi Nikkornos, thanks A LOT!
i unfortunately do not have the money to buy a sekonic (btw you know where to find one for a good price? and i'm looking for the 208 instead) and i think the cost of all the stuff above is relatively low.
I don't have the circuit diagram of it, but other people on the internet who have done it say that the process is quite simple, it's basically just replacing 2 parts of the meter with 2 new parts (solar cell and potentiometer)

 

[Achim Reh]

well, it should work, if your ant to safe the money. You just have to have a light meter to compare and calibrate the values you reading on your self built unit, and then create some sort of translation...ether graphical on a scale , or digital or with a written table. Keep in mind that a solar cell out put is not linear , and an increase in light does not have a corresponding proportional increase in output voltage.

 

[virtualme78]

Or alternatively you can use an iphone lightmeter but that is provided if your primary usage isnt for studio.

 

[oystershred]

yup, i have been using an iphone lightmeter but i think it can be a bit attention drawing, although i usually try to guesstimate from the first reading i get from it. the original intention for getting the metraphot was cos it was small (and quite cheap for the price i got it).

anw i just took apart the metraphot yesterday and put it back together. I almost fainted and it took me about 2 hours to put back together, and now i have an extra screw. hopefully this thing manages to work out