Timer to trigger another timed pulse

[ron2k_1]

Hi all,

First post here. Full disclosure: I'm no where near qualified of building this on my own. My background is in accounting, but I'm a nerd by nature. I read a lot, and definitely not afraid of trying out new things. And this here is pretty cool (and inexpensive) to try. Kindly indulge me with some of your precious time and knowledge....

So in essence what I want to accomplish is that when my car alarm goes off, I want it to trigger a phone call to my cell phone using timer control switches like those below and one of those old phones with keypad that allow you press and hold a key [for about 3 seconds] to autodial a number.

My thought is that I need to buy 2 of these:
http://amzn.com/B00GIBTQMI

On the right hand SPDT side there is a "CB", "COM", and "CK" connection. So with my limited understanding of electronics, I think I need to do this:
1. Set the first timer board to 10 secs
2. Set the second timer board to 3 seconds
[I need 10 secs on the first switch because I don't the second timer to trigger when the horn chirps when locking or unlocking the vehicle. 3 Secs on the second switch is needed because I need it send a 3 sec pulse to the phone to trigger an autodial)

On the 10 Sec Timer control board
3. Connect a normal 12 VDC from inside the vehicle to VCC (Anode) and COMM,
4. Negative electrode to ground inside the vehicle
5. Wire "IN" to the alarm horn, to trigger only when horn is on for more than 10 sec
6. I believe CB is NC, so I need to wire CB to "IN" of the second (3 sec timer unit). I need it to trigger only after 10 seconds of "siren on" has elapsed.

On the 3 sec Timer control board:
7. VCC and Negative to a normal power supply from inside the vehicle
8. "IN" comes from CB/NC from 10 seconds timer unit
9. Wire "CK"/"NO" and COMM to the phone (Key #3) like this:

I need the pulse to start at the beginning of the timer count for at least 3 seconds.

Am I totally off guys? Please don't assume that this accountant knows anything in electronics. If you figure out there is a better way of doing it, fire away... Just keep it simple and easy to understand

 

[Arouse1973]

That's very good Ron. Two things, just make sure the current consumption of the two modules doesn't flatten your car battery after long periods of not driving. And do you not need to connect the NO contact to the trigger of the second timer and not the NC? And don't forget to wire 12 Volts to the common of the first timer so it triggers the second timer.
Adam

 

[ron2k_1]

EDIT: It seems that I should have posted this on the Circuit Help forum. Mods, kindly move if I asked for help in the wrong forum.

Two things, just make sure the current consumption of the two modules doesn't flatten your car battery after long periods of not driving.

hmnn! I didn't considered that indeed. I believe at least the first (10 sec) timer will always be on. I guess I can get away by the second timer not being on all the time if I wire the NC from the 10 secs timer to both the "VCC" and "IN" of the second (3 sec) timer. Will that be safe or accurate for power saving?

And do you not need to connect the NO contact to the trigger of the second timer and not the NC?

For all I know, you may be correct. I'm just basing myself from the first (most helpful) reviewer of the amazon link I provided. He states "During the timer operation - the "COM" is routed to the "CK" connector". I guess it doesn't hurt to test all that when it gets here. But I wanted to know that what I wanted to do is possible, and that I was in the right track before ordering anything. I live in Belize by the way, so shipping and custom duties are a consideration if I order wrong components. Remember, that I want the second timer to start send a sustained (3 sec minimum) pulse at the beginning of the countdown and end on timing completion to trigger the autodial (analogous to pressing and holding phone key # 3).

And don't forget to wire 12 Volts to the common of the first timer so it triggers the second timer.
Adam

Yeah, I'm doing that on my 3rd step. I was going to wire both the VCC and COMM of the first timer from the same source. Is that safe?

And lastly, I didn't ask this in my first post. Do I need to provide power to the COMM of the second timer? All I need for the phone to trigger an autodial on key # 3 is for there to be a closed circuit or a short between to the 2 cables leading to that button.

Thanks for your response.

Ron

 

[Arouse1973]

Ok I thought by looking at the module is that the first push button sets the delay before on and the second the delay of on? For the phone button contact no power is needed you are just using the relay as a switch.
Adam

 

[hevans1944]

There are three terminals (CK, COM, CB) connected to a single-pole, double-throw, relay. These three terminal are located at the same end of the board where the relay is located. These three terminals connect only to the relay, not to other circuits on the board.

There is a normally-closed relay contact between COM and CB. There is a connection between COM and CB (contacts closed) only when the relay IS NOT actuated.

There is a normally-open relay contact between COM and CK. There is a connection between COM and CK (contacts closed) only when the relay IS actuated.

It appears that the original intent of this delay timer board is to turn on a load connected in series with a power source and the COM and CK terminals. In other words, when the relay is actuated (powered) by the time delay board, the COM and CK terminals close to complete a circuit to power an external load. COM and CK are open if there is no power applied between the VCC and GND terminals, located at the other end of the time delay board. After power is applied between VCC and GND, COM and CK will be open until the timer is triggered. COM and CK will be open again after a previously triggered time delay has completed. In other words, COM and CK are closed only while the time delay count-down is in effect.

After power has been applied to VCC and GND, the normal state of the relay is de-actuated and the two push-buttons can be used to set a new time delay interval. Or, if no buttons are pressed, the previous time delay interval is retrieved from a non-volatile memory and used for the next triggered time delay interval. The delay timer board draws a minimal current under these conditions, about 50 mA if you believe the data supplied by Amazon and others. An additional 10 mA is drawn by the relay coil when it is actuated during a delay time interval. Therefore, the normal power-on state of the time delay board is (1) ready to count down and (2) relay de-actuated.

There is a somewhat confusing statement that after power up, the numeric displays can be blanked by pressing the left push-button switch to conserve power. Your mileage may vary on this point. I don't have one of these modules to verify whether or not there really is a display blanking mode.

A momentary "high" connection between the IN pin and GND will start the time delay interval. This can be a simple switch contact between VCC and IN that is momentarily closed or 12 V from the vehicle horn. This connection between IN and GND must be opened before another time delay interval can be triggered. You have to decide whether or not to repeat speed dial the cell phone if the horn alternates between on and off, as most do, when the burglar alarm is tripped as this action will trigger the ten-second delay timer again.

When the time delay interval is triggered two things happen: (1) the relay is actuated, closing a circuit between COM and CK and opening a circuit between COM and CB; (2) the pre-set time on the display begins counting down to zero.

At the end of the count-down interval the relay is de-actuated, opening the circuit between COM and CK and closing the circuit between COM and CB. If IN is low or not connected to VCC, the timer can be triggered again to repeat the time delay interval by bringing IN high again.

So far, so good. You connect the horn "hot" wire to the IN terminal, connect GND to the vehicle chassis, and connect VCC to a live vehicle 12 V battery terminal. The timer board stays energized as long as VCC has 12 V applied. You set the timer for 10 seconds and await for the horn to blow.

The second timer has VCC and GND wired the same way as the first one, i.e., parallel connections to the same connections on the first timer. Connect the IN terminal on the second timer to the normally closed CB contacts on the first timer and connect COM terminal on the first timer to VCC. You can also try to power the second timer from the CB contacts on the first timer, as you suggested in a previous post. Won't hurt anything and it might work.This connection to CB on the first timer may cause the second timer to start its three-second delay as soon as power is applied since the relay on the first ten-second timer is de-actuated, but if the cell phone is turned off that can be ignored. Set the 3 second delay on the second timer after both timers are powered on, unless you have already set it while wiring all this up and testing it (recommended). You may have to temporarily remove the wire to the IN terminal of the second timer to allow it to be set. Re-connecting the IN wire will cause the second timer to start its three-second countdown, but if the cell phone is turned off you can ignore that. Connect the cell phone number button (as you have shown in your picture) to the COM and CK (normally open) terminals of the second timer. These contacts will close for three seconds after the second timer is triggered. If the horn re-triggers the first timer, the cycle will repeat and speed-dial again. This might not be a bad idea as it increases the chance you will get at least one call from the cell phone.

You should also install a switch somewhere in the vehicle to apply power to the delay timers and allow testing them by turning the switch on and operating the horn manually.

 

[ron2k_1]

@hevans1944

Wow! Great explanation. It seems that I wasn't that far off then. Thank you for your detailed writeup. I'll go ahead and order the components and read over (couple times highly likely) your post so as to follow better when modules and connections are already here. I have a breadboard where I can test the configuration.

Thanks guys.

R0n

 

[hevans1944]

Look also at the two breadboard pictures posted in the reviews on the Amazon site. They show two timers connected in a loop so the first triggers the second which triggers the first again.