Hi guys, i've been trying to build a circuit that would substitute a DPDT relay using transistors with full isolation, yet i am still no where.....any idea ???

thanks
Adam

 

How much voltage / current are you switching?

 

What do you mean by "full isolation"? Normally you isolate either the inputs or the outputs, but not both.

I don't think you can get behavior equivalent to a relay with a BJT. You might have better luck with a FET, or a BJT controlling the gate of a FET.

Would some kind of opto-isolator possibly fulfil your requirements?

 

Well, I have a DPDT relay; one of the poles is connected to the positive lead of a capacitor “47MF- 16V” and one of the throws is connected to the positive of 12 V DC power supply, the third throw is connected to a transistor, the capacitor charges itself when the relay is OFF then when the relay turns ON the capacitor discharges itself into the transistor, so what I really want is to replace this mechanical relay with transistors circuit.

Thanks

 

A flasher? Helpful to post a schematic.

 

like Flip Flop?? it would be a good idea, i might get some hint, thanks

 

Ok then post YOUR schematic. What's it controlling? What's it's purpose?

 

Well, I have a DPDT relay; one of the poles is connected to the positive lead of a capacitor “47MF- 16V” and one of the throws is connected to the positive of 12 V DC power supply, the third throw is connected to a transistor, the capacitor charges itself when the relay is OFF then when the relay turns ON the capacitor discharges itself into the transistor, so what I really want is to replace this mechanical relay with transistors circuit.

Thanks

What about the other pole, and why the need for isolation?

 

Well, I have a DPDT relay; one of the poles is connected to the positive lead of a capacitor “47MF- 16V” and one of the throws is connected to the positive of 12 V DC power supply, the third throw is connected to a transistor, the capacitor charges itself when the relay is OFF then when the relay turns ON the capacitor discharges itself into the transistor, so what I really want is to replace this mechanical relay with transistors circuit.

Thanks

Is this any where close to what you have right now?

 

It looks like a low tech version of Linear Technology's flying capacitor. See the end of the article - http://engr.nmsu.edu/~etti/3_3/3_3g.html

 

This is just something to get ideas rolling.