glitch noise

[Calamar]

This is the story:

I have a audio generator, very old, and when I turn it on
the metter of it get out of scale, at the same time
a single board, MC(16f877 or18f452) and lcd , source with a
lm7805, is reseted or hung-up, I used a metalic enclosure but
the problem keep going on, if I use a 9VDV battery it desappear
... I used severals source of power, 12V and 24V regulated sources,

should anyone tell me about a good design source suply for
microcontrollers, Is not apropieate the lm7805 for MC aplications ?
or single I must use a beeter filter beefore it ?

1000uF, .22uF before lm7805 and .1uF after lm7805
.1uF for each IC int the board
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)

[drolleman]

you are using electrolitics as caps place some .001 uf ceramics close to the power pins on the chip. the reason is freq responce of ceramics is much higher and will filter these freq out.

[valemike]

Your power supply might be okay.

you might be having a glitchy MCLR line though.

This is what i did when my PIC kept resetting. Look at the circuitry:

http://www.iit.edu/~valemic1/reset_circuit.jpg

you might need to magnify the image when it first loads.

-Mike

[Calamar]

Thank for reply

Colud yo send me the .jpg??
the serrver is currently down
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)

[kender]

I had a similar problem. I have built an intelligent load box for a medical RF generator. In the first revision of the board my 18F442 was resetting 38 seconds sharp after RF was applied. In the second revision I have optically isolated the RF section, and the problem disappeared.

Cheers,
Nick

[valemike]