alarm clock question

[Jon]

I have a digital alarm clock. I want to wire the alarm signal to activate a
fire bell. The fire bell is 120vac @ 40mA. The alarm signal from the clock
is around 1.5 vdc.

I found a connection on the alarm clock that is 7.5 vdc all the time.

I have 5vdc relays with contacts rated for 6 amps. I have some 5vdc reed
relays. None of them work for the 1.5 vdc alarm signal. I tried messing
with some transistors but I don't know enough about them to rig something
up. I have a bunch of resistors and capacitors.

I have a second alarm clock where the alarm is connected to a small speaker.
I'd like the fire alarm to go off when the speaker beeps a signal or when
the radio alarm goes off.

Any suggestions?

Jon

 

[Jan Panteltje]

On a sunny day (Sun, 21 Feb 2010 12:20:41 -0500) it happened "Jon"
<jon8338@peoplepc.com> wrote in
<abydnSU_ouvw9hzWnZ2dnUVZ_qOdnZ2d@earthlink.com>:

I have a digital alarm clock. I want to wire the alarm signal to activate a
fire bell. The fire bell is 120vac @ 40mA. The alarm signal from the clock
is around 1.5 vdc.

I found a connection on the alarm clock that is 7.5 vdc all the time.

I have 5vdc relays with contacts rated for 6 amps. I have some 5vdc reed
relays. None of them work for the 1.5 vdc alarm signal. I tried messing
with some transistors but I don't know enough about them to rig something
up. I have a bunch of resistors and capacitors.

I have a second alarm clock where the alarm is connected to a small speaker.
I'd like the fire alarm to go off when the speaker beeps a signal or when
the radio alarm goes off.

Any suggestions?

Jon |\| |\| +5V
+ 7.5 V --| |---| |-------------------

|/| |/| | | |
Si doides | | | -------- bell ----
| --- | | |
=== / \ | o |
--- --- [ \ ] | 120V AC
|100uF | | o |
| |------- | |
| b |/ c ------------------
1.5V DC --- R 1500 ---)---- | NPN relay
| |\\ e 5V
| |
GND ----------------------

Something like this perhaps?

 

[Jon]

Thank you Jan. Using your help I wired the transistor in and my fire alarm
clock works! I used a capacitor and two resistors, no diodes, and a
transistor. Jon


"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:hlrvro$bop$1@news.albasani.net...

On a sunny day (Sun, 21 Feb 2010 12:20:41 -0500) it happened "Jon"
jon8338@peoplepc.com> wrote in
abydnSU_ouvw9hzWnZ2dnUVZ_qOdnZ2d@earthlink.com>:

I have a digital alarm clock. I want to wire the alarm signal to activate
a
fire bell. The fire bell is 120vac @ 40mA. The alarm signal from the
clock
is around 1.5 vdc.

I found a connection on the alarm clock that is 7.5 vdc all the time.

I have 5vdc relays with contacts rated for 6 amps. I have some 5vdc reed
relays. None of them work for the 1.5 vdc alarm signal. I tried messing
with some transistors but I don't know enough about them to rig something
up. I have a bunch of resistors and capacitors.

I have a second alarm clock where the alarm is connected to a small
speaker.
I'd like the fire alarm to go off when the speaker beeps a signal or when
the radio alarm goes off.

Any suggestions?

Jon |\| |\| +5V
+ 7.5 V --| |---| |-------------------
|/| |/| | | |
Si doides | | | -------- bell ----
| --- | | |
=== / \ | o |
--- --- [ \ ] | 120V AC
|100uF | | o |
| |------- | |
| b |/ c ------------------
1.5V DC --- R 1500 ---)---- | NPN relay
| |\\ e 5V
| |
GND ----------------------

Something like this perhaps?