Matrix user forums

Hi,

I am trying to build a simple power supply for a diy project, it consists of an i2c 4 x 20 display, a pic 16f1824 and a 5 volt songle relay, I have built an LM2567 -5 3amp 5v supply which I can run off a 12 volt battery detailed here:

http://www.ti.com/lit/ds/symlink/lm2576.pdf

and attached it to my breadboard but when I start it up it powers everything but when the relay kicks in the display goes dim, could this be because I am using a breadboard with long loose wires everywhere ? or should I be using a different power supply ? as ever any information is greatly appreciated.

thanks
Stuart

Hi Stuart

Personally I wouldn't use 5 volts to power drive a relay coil I would keep coils etc. well away from the 5 volts.
I would use a transistor relay driver from 12 volts supply.

have you seen the layout guides ? these devices are quite finicky they like low impedance supply and ground interconnections.(try doubling up your links and tidying up your wires make as short as possible)

Also I am not sure if the added inductance to ground upsets the regulation with the relay energised.

A relay driver circuit can be found on the relay board eblock

http://www.matrixtsl.com/resources/file ... 8-30-1.pdf

Steve

Hi Steve,

So what you are saying is use the 5v out from the microcontroller to switch the negative side of a 12 volt circuit switching the relay instead of switching the negative side of a 5 volts switching the relay ?

thanks
Stuart

Hi Stuart

you use the output of the micro to drive a transistor this the can be used to switch a higher separate voltage circuit such as the 12 volts to power your relay.

A relay driver example attached along with a micro controller interfacing circuits pdf that i found on here some time ago
(thank you who ever posted this)

Steve

Hi Steve,

That's brilliant thanks.

Stuart