40X2 not working at 5V

[gerardshaw]

Hi,

I'm hoping someone can help me here. I have a 40X2 (PIC18F45K22). I have it connected to a 5V supply, which is exactly 5V (LM2596-5). With this the chip will not run. If I connect an external DC supply at 5.1V, it works! Can anyone explain or help me here please. Finding this very odd. the PIC spec sheet has a very wide voltage tolerance.
Thanks

 

[eclectic]

Welcome.

And the first question..

Can you provide a full schematic?

e

 

[gerardshaw]

Hi,

This is the power supply circuit. There is very little else. All i need to do to get it working is inject 5.1V at the 5V point and off it goes!

Gerard

 

[AllyCat]

Hi Gerard,

The diagram has the Feedback and Output terminals mis-labelled (exchanged). Is it actually wired up correctly?

Cheers, Alan.

 

[westaust55]

What happens if you try to operate the PICAXE from three fresh AA batteries (=4.5 volts).

That would help define if the power supply or the PICAXE chip is the key to the problem.

 

[gerardshaw]

Hi Alan,

I see you are correct. I will swap these two and try again.

Hi West,

I have not tried a lower voltage. Looking at the datasheet I would say this is the problem. Got to resolder and try again!

Thanks guys, never seen that.

Gerard

 

[gerardshaw]

Hi Guys,

That's it problem sort, time for bed now!
You were correct Alan, 2 & 4 were swapped. Quick solder job and working!

Gerard