$4 at the local electronics store...

S

Stu :)

Guest
...buys you all the parts to make your own light meter!

I got the idea from a poster at a friends work place. He's got a poster of semi-conductors on his office wall (I myself had a Sisters of Mercy poster) and read the description and uses of a certain NPN low-power transistor. Somewhere back beyond in the grey matter, something of the order of 15 Watts lit up and went "ding".

$4NZ Later at Dick Smith... armed with bunch of transistors, seven LEDs, a LDR and way too many resistors, I've turned the rough caffeine induced theory straight into working beard board prototype, a rare event for me. Now it's a matter of fine tuning the resistors to the correct ƒ-stop.

The planned finished result is a basic sunny-16 light meter that outputs a reading on scale of ƒ2, 2.8, 4, 5.6, 8, 11 and 16. So using the sunny-16 rule; if ƒ16 lights up I shoot at 125th/sec @ ƒ16 if I'm using ISO 100 film or 500th/sec @ ƒ16 if using ISO 400 film. Or 1000th/sec @ ƒ5.6 on ISO 100 or 2000th/sec @ ƒ8 on ISO 400, etc etc.

Stu :)
 
I hope you're incorporating the obligatory piece of No. 8 fencing wire used in all great New Zealand DIY jobs.
 
Ohhh... I forgot about the number 8 fencing wire... back to design board :D

Stu :)
 
Stu, I'd like to hear (and see) more about this.
I'm always admiring DIY jobs, althoug this one seems a bit... well, impractical, to say the least. If the gadget ends up to be the size of Bessa R, I don't see the point, unless it's a proof of concept.
Not to discourage you or anything - I'd still like to see how it turns out, even without No. 8 wire :D

Denis
 
oOdanoOn-
Schematics?!? There isn't one yet, well not that I'm aware of. So far it's crazy idea in my head and by some grace of a god, it happens works on bread board (prototype board).
Perhaps I should do a circuit drawing...

Denis-
Yes some people would call it impractical. But many thought the Bessa L was impractical too, look where it's gone now. Not that I'm expecting this side project to take on Gossen and Sekonic. But who would say no to a cheap $10 Stu16 meter... "Whoops I've just dropped it into the sea/onto some rocks/anything else bad".
Regarding the size, the prototype can fit in a cassette tape case. With some more thought and engineering it would fit into 120 flim box using standard off the shelf parts. If I hunted down some surface mount parts and got real cunning with PCB printing, the completed circuit board could be fitted to a Zorki.

Taffer-
Let just say for now... Stu's Cheapass Light Meter PAT.PENDING... PENDING
If the prototype works well, it will be followed up with half a dozen field prototypes that will be given away and feedback collected. If the feedback is positive, I'll make some more and see where it goes.

Stu :)
 
o0dano0o said:
can you point us to a schematic of this?

thanks
Click to expand...

Radio Shack has changed a lot over the last 10 years. However, if they still sell the Forrest Mims booklets, check them. I seem to recall that he had two or three different schematics for making light meters. Iirc they were in at least two of the booklets.
 
Unfortunately, I don't think Radio Shack carries Forrest Mim's books any longer. I think I have kept Mim's original booklet, and I also think I've kept several schematics for light sensitive circuits. If anybody needs one, please let me know, and I'll start the hunt.

Jon
 
Forrest is a friend. We met a couple of years ago when our kids were both at the State Science Fair. He lives only about 50 miles from me. He may have some sources for reprints if anyone is interested.

-Paul
 
Stu :) said:
...buys you all the parts to make your own light meter!

$4NZ Later at Dick Smith... armed with bunch of transistors, seven LEDs, a LDR and way too many resistors, I've turned the rough caffeine induced theory straight into working beard board prototype, a rare event for me. Now it's a matter of fine tuning the resistors to the correct ƒ-stop.
Click to expand...

What's a "beard board?" Sounds hairy.

LOL!

Just kidding, sounds like a lot of fun!

I quit doing electronics - I'm color-blind.

Best Regards,

Bill Mattocks
 
Stu :) said:
Taffer-
Let just say for now... Stu's Cheapass Light Meter PAT.PENDING... PENDING
If the prototype works well, it will be followed up with half a dozen field prototypes that will be given away and feedback collected. If the feedback is positive, I'll make some more and see where it goes.

Stu :)
Click to expand...

SCLM ? Sounds good ! Btw the 27B/6 comes from the movie 'Brazil', your #8 fenced wire just made me think about that passage for some odd reason :p
 
taffer said:
SCLM ? Sounds good ! Btw the 27B/6 comes from the movie 'Brazil', your #8 fenced wire just made me think about that passage for some odd reason :p
Click to expand...

Here is a receipt for your husband, and here is a receipt for your receipt.

Best Regards,

Bill Mattocks
 
Stu :) said:
... Stu's Cheapass Light Meter PAT.PENDING...
Click to expand...

I wouldn't want one unless it's got some duct tape on it. All great inventions have at least a little duct tape.

I suppose fencing wire in NZ is similar to baling wire in the US. Usually pronounced "baiylen wahr" around here. I think it's what holding up the exhaust systems of most trucks in Oklahoma. :)
 
Hey, to make this really fun, you need to find a second hand theodolite system. Thats one of those things they use on missle ranges. It has seats for two people, and it allows you to track a missle or plane by cranking the optical system around, you know, one of those with 1,000,000mm telephotos. Hook the photocell system to it and you have a great spotmeter. I like these kinds of projects. They keep me from doing something useful, like cleaning out the garage.
 
pukupi said:
I hope you're incorporating the obligatory piece of No. 8 fencing wire used in all great New Zealand DIY jobs.
Click to expand...
.......................
And to make North American's happy, be sure to hold the thing together with duct tape :D
Ala' Mr. Red-Green - LOL
 
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