[AMRadio] Voltage regulator


Barrie Smith barrie at centric.net
Sat Mar 18 20:09:37 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

Jim:

I knew I'd find someone smarter than I here!  That's exactly what's 
happening, but I didn't know one could run without the cap.


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

I have done that!

TNX, Barrie, W7ALW
>
> 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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