Manipulating a Digital watch For alarm circuit

[dstroya]

Hi guys,the last project worked really well,I'm grateful for that.I have a new one and I came up with this idea.We have to still make an alarm circuit,but now it has to be fresh out of the oven lol.I am using normal digital wrist watches .I have managed to power the watch with my own supply which uses a zener diode.The thing i need help with is the alarm beeps.I need those alarm beeps to go on constant like beeeeeeeeeeeeeeep with no interruptions.The current beep goes beep beep off beep beep off etc.I in turn need to take this constant beep and trigger a 555 timer which will cause a 4018 to count .So just need some guidelines please on how I am able to achieve this.It must work with the same concept of my previous post

Thanx guys
dstroya

 

[ghostman11]

i am not aware of your previous post so might be an idea to post a link to it. interesting project what is it actualy for?/ment to do? i assume you dont have to have the watch on your wrist while it does all this? personaly i would think it pretty hard to get a constant BEEEEPPPPPPPPP but others may know better

 

[Menticol]

Use a SCR. When a positive voltage is applied to the gate the SCR keeps conducting until the power is removed from the anode or cathode.

I have successfully used the C-106 on a simple 9V burglar alarm, but I don't know if your wrist watch provides enough power to trigger it.

View attachment 64605

Here's the C-106 datasheet

http://www.datasheetcatalog.org/datasheet/motorola/C106.pdf

And this is the website where I got the image. The automatic translation is garbage but don't worry, It doesn't say anything new.

http://translate.google.com/transla...basica/circuitos-conmutacion-scr-tic-106-rele

 

[BioniC187]

If you want to make a 555 and 4018 count, you need to run the 555 in a square wave output setup, just google "555 square wave circuit" many hits, and you can set how fast the pulses are, which in turn means how fast the 4018 counts. How are these beeps generated? from the clock pulse?

 

[MrAl]

Hi,

I actually did this a long long time ago (way back somewhere in the 1980's) but instead of a wrist watch i used a digital alarm clock. The goal was to provide a 120vac output to plug something in like a record player (yeah we had them back then) when the alarm went off.
Same problem. The alarm would beep rather than stay on constant.

The solution was to use a capacitor that is charged with the alarm signal through a diode, and the circuit it triggers is made to have high input resistance. This means when the alarm sounds it charges the cap and the cap doesnt discharge very quickly so it maintains its voltage to keep the next circuit turned on.

The other problem found was that after 5 or 10 minutes the alarm would turn off, which means the cap voltage would die off and turn the circuit off. The solution there was to use a latch. It was simple enough and cheap enough so that was that. the latch means that when the alarm turns on it triggers the latch and the latch holds the logic state until a reset button is pressed.

I also like the SCR idea however, where the SCR is turned on via the gate triggered by the alarm signal. The SCR will stay on forever unless the power is removed. The reset button could then be nothing mone than a normally closed switch in series with the anode or cathode of the SCR. When the button is pressed, the SCR turns off. This of course means sometimes you'll also have to turn the alarm off though for times when you hit the reset switch soon after the SCR fires because the gate signal will again appear to turn it back on again. There are ways around this too if needed.

 

[BioniC187]

555 timer in monostable will stay high, till reset trigger

 

[dstroya]

guys I just want to 1st thank you all for your input.The current problem is that when i power the watch with a 2.4v zener.There is a constant voltage coming out the speaker even if the alarm is not set.This poses a problem because the buzzer which i used as an output goes on all the time,but when the watch is powered with a 1.5v watch cell there is no voltage at the speaker outputs.There is only voltage when the alarm rings.only then I can apply it to a positive retriggerble monostable.can you please post a diagram where i can input the signal into the monostable.There are 3 wires coming out of the watch.It's the watches ground.the watches positive power which is common to both the watch and speaker.and then finally a ground for the speaker.This has been an exciting project with many obstacles but thanx to you guys its getting better every hour minute second lol.

 

[dstroya]

Digtal watch project

Hi,

I actually did this a long long time ago (way back somewhere in the 1980's) but instead of a wrist watch i used a digital alarm clock. The goal was to provide a 120vac output to plug something in like a record player (yeah we had them back then) when the alarm went off.
Same problem. The alarm would beep rather than stay on constant.

The solution was to use a capacitor that is charged with the alarm signal through a diode, and the circuit it triggers is made to have high input resistance. This means when the alarm sounds it charges the cap and the cap doesnt discharge very quickly so it maintains its voltage to keep the next circuit turned on.

The other problem found was that after 5 or 10 minutes the alarm would turn off, which means the cap voltage would die off and turn the circuit off. The solution there was to use a latch. It was simple enough and cheap enough so that was that. the latch means that when the alarm turns on it triggers the latch and the latch holds the logic state until a reset button is pressed.

I also like the SCR idea however, where the SCR is turned on via the gate triggered by the alarm signal. The SCR will stay on forever unless the power is removed. The reset button could then be nothing mone than a normally closed switch in series with the anode or cathode of the SCR. When the button is pressed, the SCR turns off. This of course means sometimes you'll also have to turn the alarm off though for times when you hit the reset switch soon after the SCR fires because the gate signal will again appear to turn it back on again. There are ways around this too if needed.

guys I just want to 1st thank you all for your input.The current problem is that when i power the watch with a 2.4v zener.There is a constant voltage coming out the speaker even if the alarm is not set.This poses a problem because the buzzer which i used as an output goes on all the time,but when the watch is powered with a 1.5v watch cell there is no voltage at the speaker outputs.There is only voltage when the alarm rings.only then I can apply it to a positive retriggerble monostable.can you please post a diagram where i can input the signal into the monostable.There are 3 wires coming out of the watch.It's the watches ground.the watches positive power which is common to both the watch and speaker.and then finally a ground for the speaker.This has been an exciting project with many obstacles but thanx to you guys its getting better every hour minute second lol.

 

[MrAl]

Hi,

Are you saying that the watch works normally at 1.5v but doesnt work normally at 2.4v ??

If so, then the obvious thing to try is to try to drop the voltage of the 2.4v zener a little. To do this you can try using a regular silicon diode in series with the watch power input. The diode will drop about 0.6 to 0.7v which will put the watch input at around 1.7v which might be just enough. Might also need a small filter cap after the diode.

 

[dstroya]

Its true what you have proposed,but what i dont understand is when i drop the voltage to 1.7.the watch switches off when the alarm beeps and then restarts.

 

[alec_t]

Did you use the cap after the diode, as suggested? 100μF or thereabouts?