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Re: Looking for a Low Cost On Delay Timer



On 2013-09-30, Guv Bob <guvbob2003@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> "John Sowden" <jsowden@xxxxxxxxxxxxxxxxxx> wrote in message news:l242ch$4tb$1@xxxxxxxxxxxxxxxx
>> On 08/21/2013 10:39 AM, Guv Bob wrote:
>> > Names can be confusing, so here's what I'm doing....
>> >
>> > http://img43.imageshack.us/img43/7434/wvm.gif
>> >
>> > When 12VDC is applied to the input, I need a 12VDC output for 5 seconds.  Then output will go back off and stay off until the input goes to zero.  Then cycle starts again.
>> >
>> > Current for both legs is in the 10-50ma range.

10-50ma into 3000uf? Makes for a rather long switchon time.


>> >
>> > A simple on-delay timer would work but I'm having trouble finding one with NC contacts.  Tons of stuff $100+, but for this application, it has to be under $20.
>> >
>> > Thanks,
>> >
>> >
>> > Bob
>> >
>> Get a sensitive relay (coil 1k ohms or so), put about a 3ooo uf
>> capacitor across the coil, apply 12 volts to the coil, the relay will
>> hold closed while the cap is discharging into the coil.  Use the n/o
>> contacts to do what you want.


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