The back emf diode slows the relay a lot and you can improve that with a
resistor in series, fudge as required.
Here's another method:
in the drive transistor circuit, fit a small capacitor between collector and
base. As the back emf builds up, a current will be fed back to the base
which will tend to keep the transistor on. This results in a slower rise
time and this can be controlled with the value of capacitor used. A
resistor in series with the capacitor provides even more control. Fudge as
required.
David
G3UNA
----- Original Message -----
From: "Brad Denison" <brad.denison@gmail.com>
To: <topband@contesting.com>
Sent: Saturday, December 23, 2017 3:51 PM
Subject: Topband: Detuning Relay Flyback Diode
I have a couple of 6ms 12V Kilovac relays wired up as a detuning circuit
during RX. One question comes up before implementation regarding flyback
diodes - would they be needed? Seeking opinions on this question. The
relays are powered during TX and not powered for RX direct keyed by the
radio with no sequencer.
Thanks,
Brad W1NT <http://w1nt.com>
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|