12volt Power Supply ?

[acestu]

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:

https://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

 

[chemelec]

Maybe your 100uH Choke is Not good enough.

 

[acestu]

Hi Chemelec,

These are the coils that I bought and are 6amp:

**broken link removed**

thanks
Stuart

 

[chemelec]

That Coil should be OK, so not sure What your problem is.
Possibly ADD a Better Filtering Cap on your 5 Volts. Another 1000 or 2200uF cap.
Does your relay coil have Diode protection?

 

[acestu]

hi chemelec,

Thanks for your advice I will try another cap

Stuart

 

[acestu]

P.S. I have a 1N4001 diode across the relay coil

Thanks
Stuart

 

[crutschow]

Did follow the basic layout shown in Figure 26 in the data sheet, with the components showing the heavy leads directly connected to the IC pins?
That circuit will not work well if you are using a solder-less, plug-in breadboard.

 

[dr pepper]

Too low a current rating choke is a common problem when building a switching supply, but the one you show ought to be Ok for 3a of input current.
I've had all kinds of issues with smps's made on breadboards, it could well be your problem, try putting the circuit on a bit of protoboard, and solder reasonable guage copper wire to the end rows to act as ground & power rails.