[AMRadio] Voltage regulator


Jim candela jcandela at prodigy.net
Sat Mar 18 20:03:15 EST 2006



Barrie,

I guess you are using a transformer, rectifier, and filter capacitor. The
capacitor is charging up to the peak value of the AC waveform. You could go
all out and make nice DC with regulators, and such, but for relays do you
really need that? If your rectifier is full wave then just remove the
capacitor filter, and the rectified DC will likely be fine to energize a DC
relay. A half wave rectified DC might not do too well since the relay might
buzz away.

It helps to put a diode across the coil (cathode to + end) to suppress the
back EMF when you turn off the relay.

Jim
WD5JKO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of Barrie Smith
Sent: Saturday, March 18, 2006 6:47 PM
To: Discussion of AM Radio
Subject: [AMRadio] Voltage regulator


This last week I built a 12 volt and 24 volt power supply in one small box
to power various relays around the shack.

Well, the 12 volt turned out to be 16 volts, and the 24 volt is 36 volts.
Even loaded the voltage is high.

I've done quite a bit of Googling on the subject of three-terminal voltage
regulators, but have found nothing that had actual component values that
would be pertinent to my needs.

Also saw a three-terminal using a pass-transistor. Again, no actual
component values.

I'd like to be able to get the voltages down to more nearly what I need so
that I don't burn out a relay.  Perhaps 14 volts and 26 to 28 volts, at an
amp or so.

My knowledge of solid-state devices is close to zero.

Anyone have some ideas?

73, Barrie, W7ALW


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