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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? 



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,

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,

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.

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?


Stuff with interfaces between mains and low voltage circuitry usually,

The relays are there to isolate your camera from the box. You could try replacing them with optoisolators like these

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



6 years ago

Because you don't know the impedance circuit values of the target camera.