Electronics problem, Help required.

[Mike Steward]

I would like to run my new Radio / CD Player from a separate timer partly as
bed side alarm and partly as a means to record programs when I'm out.

My multi function timer used to switch my old mains powered radio on by
simply switching on the mains supply, but with the new Radio / CD Player
the mains power has to be on all the time to maintain the tuning memory etc.

To switch the set on a simple click button is pressed which makes a pair of
contacts momentarily, just as a bell push would. to turn the set off the
button
is pressed once again.

My problem is how to make my timer simulate the pulse action. I have
connected a pair wires to the rear of the on/off button and need to be able
to
connect them briefly to turn the set on or off.

The timer switches mains. There is a ready 12 vdc within the set. I managed
to get the required affect by using 3 relays, 2 with 12 vdc coils, 1 with
240v
mains coil. But it seemed a rather clumsy way to go about it.

My question is: there another way possible with a switch.trasistor?
The two on/off switch contacts need to closed briefly when the mains comes
on and again when the mains goes off.

Sorry this explanation is a bit long winded, but to answer it one must
understand the
question.

Thank you Mike S.




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[Jamie]

use a double throw relay..
the center tap will be used to actuate a 1 shot timer.. can be made
from a 555 timer from radio shaft.. the other legs of the relay are
connected to gather and is part of the reset signal to the 555 timer.
when the relay moves from one pole to the next there will be a period
that nether contact will be making. in this time period the center arm
of the relay can thus be allowed to pull up the reset on the 555 timer.
so this means you can get a short pulse from the timer when the relay
goes to the on/off pos..
the 555 timer Vcc should always be powered up.
this pulse can drive a basic transistor to drive a simple mini relay
that you can use to actuate your switch..



Mike Steward wrote:

I would like to run my new Radio / CD Player from a separate timer partly as
bed side alarm and partly as a means to record programs when I'm out.

My multi function timer used to switch my old mains powered radio on by
simply switching on the mains supply, but with the new Radio / CD Player
the mains power has to be on all the time to maintain the tuning memory etc.

To switch the set on a simple click button is pressed which makes a pair of
contacts momentarily, just as a bell push would. to turn the set off the
button
is pressed once again.

My problem is how to make my timer simulate the pulse action. I have
connected a pair wires to the rear of the on/off button and need to be able
to
connect them briefly to turn the set on or off.

The timer switches mains. There is a ready 12 vdc within the set. I managed
to get the required affect by using 3 relays, 2 with 12 vdc coils, 1 with
240v
mains coil. But it seemed a rather clumsy way to go about it.

My question is: there another way possible with a switch.trasistor?
The two on/off switch contacts need to closed briefly when the mains comes
on and again when the mains goes off.

Sorry this explanation is a bit long winded, but to answer it one must
understand the
question.

Thank you Mike S.




---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.580 / Virus Database: 334 - Release Date: 15/11/2003