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Could I use transistors rather than relays? Answered

Im trying to build this project (link), but am short on space. Could i use 2904 transistors rather than the relays? 

-A907

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steveastroukBest Answer (author)2011-09-18

I gavea comprehensive answer to you, but since you never give best answers, I deleted it.

No, you can't use transistors, but there is a smaller alternative,

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astroboy907 (author)steveastrouk2011-09-18

Dear stevastrouk,

I must apologize for my lack of placing best answers to my last few questions. I have rather avoided them. I am sorry for that. Also- what is the proper etiquette to use? For example, someone answers the question, but the n some one else comments on their answer, but I believe their answer is better. Should I award best answer to the answeree? I cannot place best answer on the comment on the persons answer. I understand how you are angry with mee, I would hate it if someone didnt do anything after I gave an answer to them. I will give out answers hopefully by the end of the afternoon.

Best regards and apologies,
-A907

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steveastrouk (author)2011-09-18

Thanks for the Best Answer, and I have posted the correct solution for you.
In my experience the Opto-isolator is quite effective here.

There are also considerably smaller relays available than were used in the 'ible you referenced.


It is, alas, a stupid weakness of the marking system that a comment can't be best answer. You'll find that those who follow such things will always post their answers in the top.

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astroboy907 (author)steveastrouk2011-09-18

Shoot. I just placed my large order last week. I will see if I have any luck fitting in the relays, and if not, will try to get some opto-isolators. I might have some in an old piece of equipment... where are they usually found, if I may ask?

-Thanks!
-A907

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steveastrouk (author)astroboy9072011-09-18

Stuff with interfaces between mains and low voltage circuitry usually,

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steveastrouk (author)2011-09-18


The relays are there to isolate your camera from the box. You could try replacing them with optoisolators like these
http://uk.farnell.com/isocom/til198/optocoupler-dip-8-dual-darl-o-p/dp/1683369?Ntt=1683369

They can handle up to 80ma on the isolated side, and you get two channels in one packet.

Steve

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iceng (author)2011-09-17

No.
Because you don't know the impedance circuit values of the target camera.

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