Relay control problem

[SimonM]

Hi,

I am working on a projet that uses latching relays. They latch when you put a polarity or the oposite (set = +/- reset = -/+). The problem I have is that I cannot find a way to control the relay I.E control the ground and +5v of the relay.

Is there a way to assign a I.O to ground and switch it back to +5v or something similar?

Simon

 

[wannaBinventor]

I'm not sure what you are asking exactly.

One of the most basic things a microcontroller can do is set an I/O pin to Vdd or ground.

 

[skyhawk]

H-bridge?

H bridge - Wikipedia, the free encyclopedia

 

[SimonM]

I'm not sure what you are asking exactly.

One of the most basic things a microcontroller can do is set an I/O pin to Vdd or ground.

This is exactly what I need to do actualy. I am confident that you can swap it at any time when you want? I must say that I am new to the uc design and principles. Do you have a quick example of how it works?

For the H Bridge, it is a good idea and I was thinking about it, however it introduce more hardware and it is something that I want to reduce.

Thank you both for the quick response. I truly appreciate it.


Simon

 

[cc1984]

What current does the relay require to latch the relay? If it is low enough you should be able to drive it directly from a PIC.

 

[Wilksey]

Use an NPN transistor with a back emf diode.
Put a 1k or 2k / 2.2k resistor in series with the base of the transistor and the PIC IO pin.

 

[blueroomelectronics]

Much easier to drive a dual coil latching relay.

 

[Mike - K8LH]

Maybe it is a dual coil relay (with internal diodes)?

 

[SimonM]

Thanks for all the answers and discussion about this.

THe current I draw is about 0.020 a per Relay when I toggle them. I use single coil latching device and they are not ''pulse toogle''. I must invert the polarity.
I know that dual coil are easier to drive, but I need to keep the number of input low to reduce the number of hardware on the board.

For now, I think that the only possible solution is to use a H-Bridge. I have depleted other type of solution since I got 16 relays to activate. Using a H-bridge will allow me to drive them all (actualy I divide them in two packs of 8).

Thanks for the help

Simon