|[AMRadio] Voltage regulator|
w1eof at hamnutz.com
Sun Mar 19 17:11:31 EST 2006
One diode will do it if it's not very far from the relay coils. Diodes are
cheap but you don't one on every single coil if they are all in parallel.
The whole purpose of the diode is to protect whatever is driving the coil
from the back-emf pulse. In the case of a solid state device that back-emf
can kill it instantly. A small 5VDC coil can generate a LOT of voltage when
it's field collapses.
As as the Amphenol relays go.... If they are DC coils they should have the
reverse diode on them for good measure. Of course if they are AC coils (Some
are) then you definitely should NOT use a diode.
> -----Original Message-----
> From: Barrie Smith [mailto:barrie at centric.net]
> Sent: Sunday, March 19, 2006 4:20 PM
> To: Discussion of AM Radio
> Subject: Re: [AMRadio] Voltage regulator
> Another couple of questions relative to relays this time.
> Some of my antenna relays have protective diodes and some don't.
> If a power
> supply were to be used only for switching relays, could the
> protective diode
> be placed at the output of the power supply, rather than at the relay?
> Also, looking at a couple of Amphenol coax relays I have here,
> there is not
> only a protective diode, but a (very) small disc ceramic capacitor across
> the coil.
> Further protection?
> 73, Barrie, W7ALW
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