Simple Light Break Detection

[spike47]

Hi
Am making a light break detection sensor as per attached schematic.

Question: I can't find a 5v relay with a coil resistance of 125 Ohms, I have some 5v relays at 70 Ohms would they work ?, also the diode 1n4004 , I have some 1N5397 would they do in place of the 4004 ? .

cheers
Spike

 

[ChrisP58]

At 5 volts, the 125 ohm coil will draw 40mA. A 70 ohm coil will draw 72mA. As long as your transistor has a current rating higher than that, and has enough gain to sink that current, you will be fine.

The 1N5397 will be ok. https://www.vishay.com/docs/88514/1n5391.pdf

 

[spike47]

At 5 volts, the 125 ohm coil will draw 40mA. A 70 ohm coil will draw 72mA. As long as your transistor has a current rating higher than that, and has enough gain to sink that current, you will be fine.

The 1N5397 will be ok. https://www.vishay.com/docs/88514/1n5391.pdf

Hi
Thanks for your reply.
Spike

 

[spike47]

Hi again
Is there some way to introduce a time delay into this circuit, so that after the object passes through the beam break the relay will stay activated for lets say a second later !.

cheers
Spike

 

[Pommie]

Yes. But your question is ambiguous. Do you want the relay delayed or the activation to be extended?

Mike.

 

[spike47]

Yes. But your question is ambiguous. Do you want the relay delayed or the activation to be extended?

Mike.

Hi
Thanks for your reply, sorry if not been clear, "activation to be extended" is what I would like to do .
heers
Spike

 

[spike47]

Here is what I have as a schematic by (dodgydave)

 

[wkrug]

A longer time ago I've realized that with an simple REED Contact.
The Power line to the Bulp was wrapped a few times around the reed contact - Dependend from the drawn current.
When Current to the Lamp was drawn the Contact opens.
When Lamp defect no current was drawn and the control Led lights up.