Relay Actuator One Shot

 I had a problem posed to me, the idea was to actuate a relay briefly using an applied DC voltage which couldn't be applied for less than 1 minute.  The voltage is being applied to the relay (I *think*) via an internet controlled relay.  So in other words a one shot type of circuit is needed to close the relay briefly.

I tried a Bing search with these words:

  pulsing a relay on via a series capacitor

and the top result was:

https://forum.allaboutcircuits.com/threads/need-a-circuit-to-pulse-a-relay-on-and-off.11112

I then tried the RC circuit mentioned using an old 5 volt SPDT relay from Radio Shack.  A 1000 uF cap in parallel with a 10,000 ohm resistor was used as follows:

The relay coil is about 70 ohms.  The actuation time is about 100 milliseconds.  The capacitor discharge time from 5 volts to 0.5 volts is roughly 25 seconds.

relay goes on for about a tenth of a second

Basically the same circuit can be used as a relay power saver.  The capacitor is used to handle the initial actuation current and the resistor is sized to supply the holding current for the relay coil.  As I recall Doug Demaw, W1FB used this idea for an antenna switch which used automotive 12 V relays.  But I still haven't found that article.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm