[ARC5] Backwave

[Fuqua, Bill L]

  A series diode will not accomplish much at all other than reduce voltage to the coil a bit.
The shunt diode will reduce the "flyback" voltage and increase the release time. 
73
Bill wa4lav

________________________________________
From: ARC5 [arc5-bounces at mailman.qth.net] on behalf of Jay Coward via ARC5 [arc5 at mailman.qth.net]
Sent: Monday, October 26, 2015 8:36 PM
To: k1lky68 at gmail.com; arc5 at mailman.qth.net
Subject: Re: [ARC5] Backwave

Thanks Roy for clarification. Do you think parallel And series diodes be a better way to go?
 Actually, I prefer Mike and Roberts view of minimalist intrusion of the original design.
 Jay


-----Original Message-----
From: Roy Morgan <k1lky68 at gmail.com>
To: ARC-5 List <arc5 at mailman.qth.net>
Sent: Mon, Oct 26, 2015 4:51 pm
Subject: Re: [ARC5] Backwave



On Oct 26, 2015, at 6:48 PM, Jay Coward via ARC5 <arc5 at mailman.qth.net>
wrote:

>
> Hello Everyone,
> I always thought back EMF diodes were wired
across the coil, not in series. Maybe at +28V it doesn't matter?

Do not be
confused by there being two different phenomenon going on.

The posted
URL:

http://aafradio.org/docs/Relay_timing_issues_-_SCR-274N.html

Talks
about solving a problem where one or more relays affected other relays that were
in parallel with it/them. This situation apparently caused some of the relays to
act badly.  The diodes in series with the coils isolated the relays from
affecting each other.

The more normal situation where a relay has a diode
installed backwards ACROSS its coil is done to cause the relay to open as soon
as possible after the coil voltage is removed, or to reduce transient voltages
that would otherwise be generated.  This second reason is the case especially
where the relay is being driven by a solid state device.

I don’t think the
voltage in the case of the SCR-274 transmitters was the important
factor.

Roy

Roy Morgan
k1lky68 at gmail.com
K1LKY Since
1958

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