AVR-Chat

hi every body!
i've made an ultra sonic transmitter. the signal is made by LM55 an for amplifying the current i've used a 7400 gate nand. at the end the output of 7400 is send to the sonar. it worked properly and i got the signal with my receiver. but now after one day, my signal has a lot of noise. when i unplug the NAND the noise is no more there!!! why??? 


[Non-text portions of this message have been removed]

Hi there,

 

Have you got good decoupling around the power pins of the 7400. You should
ideally have 100nF and 10nF in parallel close to the VCC pins of this
device.

 

What about generaly supply decoupling? Is this a home made PCB etc?

 

Dave.

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Sh R
Sent: 14 August 2011 14:59
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] a problem with 7400 NAND

 

  

hi every body!
i've made an ultra sonic transmitter. the signal is made by LM55 an for
amplifying the current i've used a 7400 gate nand. at the end the output of
7400 is send to the sonar. it worked properly and i got the signal with my
receiver. but now after one day, my signal has a lot of noise. when i unplug
the NAND the noise is no more there!!! why??? 






[Non-text portions of this message have been removed]

At least the 100 nF cap (depends on the frequencies you're running at) - I'm really not clear on what he's doing amplifying the current with a NAND gate instead of (for example) an Op Amp, though? I haven't done it the way he's doing it, at least, seems :) (Doesn't mean they're doing it 'wrong', there are always MANY ways to do things, and sometimes the most "linear thinking" way to do something, may be possible to really improve on by some "Sideways thinking", even though it causes brain pain at first LOL)

  Mark