Relay/Transistor like switch

[Dominik1946]

Hello everyone I'm electrical/mechanical maintenance apprentice but unfortunately I don't have anything to do with the electronics, Im trying to find a component that will work like a relay so when you apply the voltage to the coil it will make the connection on the contact, similar to transistor but with the current be able to flow in any direction not only from collector to emmiter, this have to be a minature size like the transistor, is there anything like that because relays are too big for my project.
P.S. Sorry for my english

[piratepaul]

Hi, your English is perfect.
May be a reed switch and a coil/ elecro magnet.
May be 2 transistors, when 1 is on the other is off etc.
What is it for, what current do you expect to flow?

Lots of possibilities to make the circuit work, tell me about the circuit.

[piratepaul]

I don't know if there are off the shelf components to do this, I can't think of any. Perhaps Pauldf or Richard or someone has a suggestion.
Two transistors would do it but there is switching time to consider. I/we need to know more about the circuit.
Back in a bit.

[Dominik1946]

Hey guys thanks for replay and sorry for late response, I am playing with Arduino board and the maximum current flowing through them will be what Arduino can handle, maximum of 40mA, I'm not too bothered about the switching time because the application don't require an instant switching

Circuit drawing

unnamed.jpg (28.73 KiB) Viewed 16815 times

I have make quick paint ''circuit'' drawing and I hope you guys will tel me if it would work this way, On circuit A the current will flow from the battery through the transistor on the left through the resistor, LED and back to ground or negative, circuit B is the same but this time power supply and LED has been swapped round the current has to flow different direction from the bottom through the r/h transistor to the LED and back to ground. The thing is both bases have be activated at the same time whatever way I need the current to flow because they will be operated by the single output from Arduino.

Will the above circuit work or have you got any other suggestions or devices that can do that job, thanks.

[piratepaul]

Hi, I can't get drawing B to come up on my computer,I think the problem is my computer, I will try again in the morning.

Drawing A I think only 1 transistor will work because the LED will act as a closed switch in one direction, I will have to think about resistors, I think you might need resistors in the small transistor loop.

It is late here, time for bed, back tomorrow.

[Dominik1946]

The LED is only an example, I want to be able to connect any load to that circuit all I need is that continuity so the current can flow in both direction, i know I'm making it complicated but its typical with me

[piratepaul]

Hi, I still can't get drawing B to come up, I think it must be my tablet, does it come up on yours?

The idea of the transistor loop is ( I have blown up so many transistors, there are people who understand them better than me on here) correct, protecting them with the diodes is correct, I think the collector side of the transistors should have a resistor. Current can only flow in one direction through the LED and because the battery will only supply current in that direction. If you put in another LED in the opposite direction and reverse the battery the cecond LED will light, so if you have 2 batteries and switch one on and the other off, one LED will light, switch them round and the other LED will light.
Of course the LEDs can only light when you bias the bases of the transistors to switch them on.
Switching time depends on the way you switch them on and off, they could both be switched on and left on if protected by the diodes, your idea not mine...god idea.

[Dominik1946]

Thanks a lot for your answer both circuit A and B are on the single drawing and I can display them ok, I just have ordered few parts from RS so I can see if this theory will work in practice and I will let you know how it went thanks again