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Calamar
Joined: 07 Sep 2003 Posts: 60 Location: Buenos Aires (Argentina)
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glitch noise |
Posted: Tue May 31, 2005 8:28 am |
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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) |
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drolleman Guest
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Posted: Tue May 31, 2005 8:46 am |
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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. |
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valemike Guest
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Posted: Tue May 31, 2005 8:49 am |
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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 |
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Calamar
Joined: 07 Sep 2003 Posts: 60 Location: Buenos Aires (Argentina)
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Posted: Sat Jun 04, 2005 1:03 pm |
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Thank for reply
Colud yo send me the .jpg??
the serrver is currently down _________________ Best Regards
Daniel H. Sagarra
La Plata (Argentina) |
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kender
Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley
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Posted: Sat Jun 04, 2005 9:34 pm |
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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 |
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valemike Guest
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Posted: Sun Jun 05, 2005 6:18 pm |
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Calamar wrote: | Thank for reply
Colud yo send me the .jpg??
the serrver is currently down |
Try again. I would send you the circuit picture, but I don't have your contact info. You should be able to view it. Otherwise, I took the circuit from any of the PIC datasheets. Open up the .pdf file and do a search for "External Power-On Reset Circuit (For Slow Vdd Power-Up"
Or look in the glossary and search for "reset". The circuit also acts as a filter for MCLR because of the capacitor. |
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