# Will my View Finder explode?

Discussion in 'The Projects Forum' started by alexx, May 30, 2011.

1. ### alexx Thread Starter New Member

May 29, 2011
29
0
well... not explode.. but will it be damaged?

I need to hook up my sony viewfinder from my old camera to a smaller and more portable camera like a web cam, so Q1: is a web cam a good type of camera to do this with?

My plan is to first measure the voltage and current being supplied to the viewfinder from the original old sony camera, this is what i got:

-voltage being supplied from + wire of viewfinder to - wire = 5.10 V

-current (or power?) being supplied from + wire of viewfinder to - wire = 2.03 KΩ (not too sure about the units but 2.03 is definatly the # value obtained so Q2: is the 2.03 more likely in KΩ or Ω?

-voltage supplied from + wire of viewfinder to video wire = 2.07 V

-current (or power?) from + wire of viewfinder to video wire = 4.72 KΩ

with these values my plan is to connect the positive end of a standard wal mart 9 V battery (lets say 9V #1) to the positive end of the viewfinder, then connect the negative end of the view finder to a junction with a switch and then to the negative end of the 9 V #1. the video wire of the viewfinder will go to the video wire of the webcam. the positive end of the web cam will go to a seperate 9 V battery ( lets say 9V #2). and the negative end of the webcam will go to that same switch junction, then to the - side of 9V#2. Q3 : any problems with the setup ?

the most important question Q4: how do i find out what current the old sony camera was supplying to the view finer? and after i do is this the correct next step to:

calculate the resistor i need at the - end of the viewfinder with R= (9V- 5.1 V) / current supplied by old sony

if i find that resistor value and put it in the circuit will my viewfinder work?

Thanks a lot for you time!!

2. ### Pencil Active Member

Dec 8, 2009
271
38
I have no idea what type of "viewfinder" you are working with or,
any experience with photographic equipment.

But I will try to set you on the right track to get the information
you may need. (Very basic knowledge).

See my first statement.

You are measuring resistance. The unit is Ohms (Ω).
Your measurement, if I understand correctly, is merely measuring
some of the internal circuitry. This may or may not be important.

This is hard to understand.
If you need a supply voltage less than the voltage of the battery
or battery pack look into "voltage regulator I.C.". (Example: LM7085).
One caveat is the voltage regulators of this type are wasteful of energy.
This means shortened battery life. These regulators also have specific
requirements to operate properly. There are other solutions to get the
voltage requirements needed.

Also note: 9V batteries are expensive and are usually a poor choice
for most applications for reasons other than expense. Rechargeable
NiCad or NiMH (AA or whatever) are a much better choice.

This can be measured, but it may not be necessary. The device may not
need external current limiting. In most situations (not all), the device will
only draw what current it needs.

Look into voltage regulation or building a suitable battery pack. Also see answer to quote above.

Do you have any sort of information on the three devices in question?

Are you sure the signal from "the viewfinder" can be used by the "webcam"?

Have you ever seen this done before?

If you need some "training" in electronics check out the AAC books (tabs at the top of this page).

Last edited: May 30, 2011