## Re: Electronic Terminology Was: Power question .........

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• One of the unsolved point is HOW TO WAIT TWO MINUTES before turn on the first siren. ... from 10 ... I cannot beleave this is the only one solution for this
Message 1 of 9 , Oct 4, 2002
One of the unsolved point is HOW TO WAIT TWO MINUTES before turn on
the first siren.
> or HOW TO WAIT FIVE MINUTES before turn on the second one.
>
> Think that this two minutes and five minutes must be configurable
from 10
> seconds to 6 minutes. (aproximately)
I cannot beleave this is the only one solution for this very simple
time problem.

Tony says

You are right there is a much easier and cheaper way... use a 555
timer these cost only a couple of \$ and are very reliable and can be
adjusted to suit almost any time delay, milliseconds to hours and
operate on 5 - 16 volts DC and can sink or source up to 200
milliamps which should be enough to drive your relay. The relay
would nead to have a reversed biased diode across the coil to
dissipate the back emf generated when the relay turns off. If you
like I will draw a circuit for you and post it here. I would need to
know the coil resitance of your relay this is measured in ohms

Remember every siren alarm are 12 V DC and use 1.3 Ah, so we have
2.3 Ah with 12 V DC.

***** Maths corection 1.3 + 1.3 =2.6 amps

> The electronic shop give me one relay for the TWO sirens alarms
with the
> following characteristics:
>
> ************************
> ISKRA
> TRM 3013
> _____
> 12V - - - - -
> _
> _/ _
> _ 10 A 250 ~
> _/ _
>
> ************************
>
> Which means, if I understand correctly, the resistance to control
the really
> is 12 V DC
> and this is a two ways relay for 220V AC and for 10A.
>
> BUT THE SIREN ALARM IS 12V DC and something tell me this relay is
not the
> correct one (I smell something wrong).
>
> If my alarm is 12V DC why I have one relay specification with 10A
250V AC??

Tony says

The 10 A at 250 volts is a maximum rate and should be fine for your
aplication but you would need 2 relays
Hope this helps.
Tony
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