Momentary switch after relay close

[sllimbri]

I'm trying to use a relay as a switch to contol a voice recorder that plays a message. My problen is that the relay closes for 1.5-2 seconds and this is too long. The recorder only needs a short (.5sec max) close time. Is there a way to still use the relay, but limit the output to a short pulse? The relay is part of a security system I am using.
Thanks.

 

[KMoffett]

If the relay is a "DC" type and you have access to rewire the connections to the coil, the attached circuit may work for you. The on-time is a function of the relay coil resistance and the value of the capacitor. Approximately: C(in farads) x R (in ohms) = on-time (in seconds). The diode (D) a garden variety rectifier such as 1N4001. The resistor R is a non-critical value that discharges the capacitor after the switch opens...say, anything from 1X to 10X the coil resistance.

If you don't have access to the existing relay coil, you could add this circuit with a second relay.

Ken

 

[sllimbri]

Thanks. I do have acess to the relay. I will have to look into it further.