Current/Voltage drop when LED blinks

What is the input voltage to the regulator? How stable/current sensitive is that?

Does the current drawn by the whole thing increase by the expected amount when the LED is on?

Andy Wood snipped-for-privacy@trap.ozemail.com.au

Is the status LED directly across the regulator or another micro output pin? If it is directly across the supply then it shouldn't dim, as the LM7805 has a low output resistance and can supply ample current. If it's on another output pin then the ground of the micro would be suspect. Do you have a photo of the actual construction?, this could provide vital clues.

Sounds like it's oscillating perhaps. Has your 7805 got proper bypass caps on it? What is the 7805 input voltage? Looked at it with an oscilloscope?

Tried a DC bench supply?

It shouldn't change at all, something is wrong.

What's a Wisher board?

What's this "blinky"?, the status LED I presume? What's the circuit?

Most LED's do not need to be driven at 20mA to be usable, 5mA or so is usually plenty.

Dave.

What sort of bypassing on the reg? Have you got (access to) a CRO to look at your 5V rail?

if you can scribble down the schematic, scan it, and throw it up on the web somewhere, it may help.

Cheers Don...

It was a dodgy controller. I swapped out the installed atmega8 and replaced it with another, and it worked fine.

I noted that without blinky, the circuit used 50mA: status LED, uC, and

When blinky fired, the current usage jumped to 80mA.

But in both cases, voltage remained the same.

Never did find out what blinky does with a wisher board

Wisher boards are the solderless breadboards.

The way I had the circuit setup: one board had the voltage regulator with the status LED, the seconds had the uC, and the third with the LED and resistor for the blinky hello world.

Add two 100nF ceramics to the 7805, one between input & ground, & the other between output & ground.