12v battery alarm relay questions.

Thread Starter

Hardtime72

Joined Feb 22, 2018
4
I have built a 12v battery powered driveway alarm that works through a bosch automotive relay to an adjustable time delay off relay.
The diagram I have is drawn shows 2 relays the second is actually the time delay off relay.
( https://www.amazon.com/GEREE-Module-External-Trigger-Automotive/dp/B01DDCLA3M

Screenshot_2018-02-22-12-37-42.png
The alarm works well enough with a momentary contact switch. But if the switch doesn't make long enough contact the relay won't initiate the time delay reset (power disconnect not long enough). Also if the switch is contacted and not released at all, the time delay relay won't activate until the switch is released. I dont want someone figuring out that they can trigger the switch and disable the alarm by keeping pressure on it.

Any suggestions/diagrams for a solution would be appreciated. (Thinking about installing another time delay relay but setting it for short time delay on if switch contact is made without being released.)
 

wayneh

Joined Sep 9, 2010
17,153
Instead of the first relay, you could use a 555 timer IC configured as a “one shot” monostable multivibrator. This can be set to trigger a pulse of whatever duration you like.

I think the pulse will end even if the momentary switch is held down. (This needs confirmation.) Repeated switching would re-trigger the alarm. The 555 can source and sink 200mA. Is that enough for the second relay?
 

Dodgydave

Joined Jun 22, 2012
10,082
Instead of the first relay, you could use a 555 timer IC configured as a “one shot” monostable multivibrator. This can be set to trigger a pulse of whatever duration you like.

I think the pulse will end even if the momentary switch is held down. (This needs confirmation.) Repeated switching would re-trigger the alarm. The 555 can source and sink 200mA. Is that enough for the second relay?
A 555 monostable timer wont give a pulse out if pin 2(trigger) is held low continuously, it will keep pin 3(output) high even after the time as lapsed, you need a pulsed trigger using a capacitor .


images.png
 

AnalogKid

Joined Aug 1, 2013
9,478
Let's back up a bit. What is it you want to do?
Assuming LS1 isn't just a speaker, but some kind or bell or alarm, when do you want it to sound?
Do you want it to sound for a fixed length of time whenever the switch is pressed either for a very short time or a very long time?

Your drawing is not very clear, because it looks like you have some signal lines on top of some package outlines. But it appears that when the switch is tripped, the first relay removes power from the timer relay, and when the switch is released, the first relay applies power to the timer relay, which then activates LS1 for a fixed amount of time. If this is correct, then the most simple thing is to replace both relays with one module that is built to do this job. The big question is how long does LS1 sound?

There are lots of timers on ebay. The key is to use one that has a separate trigger switch input. Connect this to the driveway switch, and the relay contacts directly to LS1.

https://www.ebay.com/itm/DC-12V-Adj...211222?hash=item2cc4acaa96:g:MjgAAOSwL9hZkt-l
https://www.ebay.com/itm/DC-12V-Del...966031?hash=item3af5254e8f:g:lWIAAOSwDkVZ7Kba

ak
 

Thread Starter

Hardtime72

Joined Feb 22, 2018
4
Sorry my drawing was not correct. See wiring of U2 relay here.
71f2KfBjTGL._SL1500_.jpg
DC with S5. AC w/o. I have wired this and it works well enough. Relay is timed by a combination of jumpers and a potentiometer. From 0.1s to 1hr. Two of the jumpers determine whether the time delay off or time delay on. Not using a gate switch just a pressure contact momentary swith (vehicle tires create contact). When power is initiated on U2 time delay off is set to 3minutes.12v 120db piezo alarm sounds. When relay time expires alarm shuts off. To start the timer on the relay again there has to be a break in contact. This would be the reset for the alarm again. Contact opens NC on first relay when momentary switch activates, breaking power supply (no connection on NO circuit) to + input on timed relay. When contact is released, power is re-initiated through NC on first relay. This initiates the time start for 3 more minutes on the time delay relay.

This works, as I have it wired. My problem is if I back over the switch as the alarm is sounding, NC on relay one goes to NO breaking the circuit that powers the timer relay. As long as contact is made with the switch no alarm. I need to remedy this.
 

sghioto

Joined Dec 31, 2017
2,416
View attachment 146812This works, as I have it wired. My problem is if I back over the switch as the alarm is sounding, NC on relay one goes to NO breaking the circuit that powers the timer relay. As long as contact is made with the switch no alarm. I need to remedy this.
If you wire the delay relay as shown in my post #5 you won't have the problem you are describing or need relay U1.
SG
EEE gate alert.png
View attachment 146857
 
Last edited:

Thread Starter

Hardtime72

Joined Feb 22, 2018
4
Works like a charm. Now to figure out distances and power supply requirements. I'll be back here if I can't figure it out.

THANK YOU!!!
 

MisterBill2

Joined Jan 23, 2018
9,785
I have built a 12v battery powered driveway alarm that works through a bosch automotive relay to an adjustable time delay off relay.
The diagram I have is drawn shows 2 relays the second is actually the time delay off relay.
( https://www.amazon.com/GEREE-Module-External-Trigger-Automotive/dp/B01DDCLA3M

View attachment 146713
The alarm works well enough with a momentary contact switch. But if the switch doesn't make long enough contact the relay won't initiate the time delay reset (power disconnect not long enough). Also if the switch is contacted and not released at all, the time delay relay won't activate until the switch is released. I dont want someone figuring out that they can trigger the switch and disable the alarm by keeping pressure on it.

Any suggestions/diagrams for a solution would be appreciated. (Thinking about installing another time delay relay but setting it for short time delay on if switch contact is made without being released.)

You can wire the first relay as a latching relay by adding a connection from the line that goes to the second relay back to the coil terminal that connects to the triggering switch. You will also need to have a normally closed switch in that line to reset the system. That is far simpler than any of the other suggestions, also more reliable and cheaper.
 
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