🚀 go-pugleaf

"Grog" <shem_an_na@SPAM_ME_NOThotmail.com> wrote in message
news:WagNb.12416$Wa.2423@news-server.bigpond.net.au...
>
> "David L. Jones" <tronnort_@yahoo.com> wrote in message
> news:4004fa1c.596911@News.CIS.DFN.DE...
> > On Wed, 14 Jan 2004 11:22:20 +1000, "LBNote" <lbonnell@ozemail.com.ua>
> > wrote:
> >
> > Your problem is most likely one of physical construction and wiring.
> > Your LED will be pulling significant current each time it switches on
> > (2mA?, 20mA? depends on your dropper resistor). If you supply your UHF
> > module via the same ground connection as your LED then the resistance
> > of your ground connection will induce a small voltage drop, enough to
> > upset your UHF module. The longer your ground connection the greater
> > the potential problem becomes.
> >
> > Good practice would be to wire seperate ground connections to your UHF
> > module and your PIC/LED circuit, from your power supply. This is
> > called a "star ground" connection. Also you would have seperate bypass
> > capacitors on each as well (right across the powerpins of each
> > device). 100nF and 10uF values are common, but their value is not
> > critical. 22uF (not mf unless you are an oldie!) is fine.
> >
> > Regards
> > Dave :)
> > ---------------------------
> > (remove the "_" from my email address to reply)
>
> Yes indeed, I'm with you on this one Dave.
>
> I had a design using the same TX/RX pair.
> The receiver would be 'upset' by an RS485 device transmitting.
> What a pain that turned out to be... Seems that with all the gain of
> the super-regen RX, the slightest power supply ripple would be
> seen on the data output. (probably mostly to do with the slicer really)
> Decoupling, decoupling and then a bit more decoupling made things
> a lot better but still not perfect. The grounding was to a bottom layer
> plane in this case and still the noise got through....

RS485 Drivers can deliver/draw quite a bit of current when they Transmit
........