# Delaying current to a relay

Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=51122
Printed Date: August 18, 2022 at 11:37 PM

Topic: Delaying current to a relay

Posted By: 704acc
Subject: Delaying current to a relay
Date Posted: March 01, 2005 at 9:52 PM

This is my first post so please bear with me.  I am using the 12 volt positive siren lead from my Viper alarm to trip a relay in addition to powering the siren.  I do not want to energize the relay when the alarm is armed/disarmed and the siren chirps, but I want the relay energized when the alarm is tripped and the siren is sounding.  Is there a way to delay the current to the relay {but not the siren} for a second or two?  I have a JPEG of the diagram if anyone can assist me with posting it.

Regards,

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Ray Kane

Replies:

Posted By: slush
Date Posted: March 01, 2005 at 10:42 PM
704acc wrote:

This is my first post so please bear with me.  I am using the 12 volt positive siren lead from my Viper alarm to trip a relay in addition to powering the siren.  I do not want to energize the relay when the alarm is armed/disarmed and the siren chirps, but I want the relay energized when the alarm is tripped and the siren is sounding.  Is there a way to delay the current to the relay {but not the siren} for a second or two?  I have a JPEG of the diagram if anyone can assist me with posting it.

Regards,

Well, as for delay you could just use the RC time constant:

T (seconds) = R (ohms) * C (farads)

For example, if you wanted a .5 second delay:

T = 10Kohm * 47uF

= 10x10^3 * 47x10^-6 ~= .47s.

You would connect the (+) to the resistor, the resistor to the capacitor's (+), and the capacitor's (-) to whatever you wanted to power on that delay.

However if you wanted the relay tripped when the alarm is tripped and the siren is sounding, you could also just use a \$1 boolean AND gate (or 2 NAND gates) from radio shack, then have it output to your relay.

Just remember to use resistors where applicable so you don't blow things out

-Derek

Date Posted: March 01, 2005 at 11:01 PM

I am a HVAC technician by trade, and we use delay timers for compressor protection. We, obviously, work on AC voltage, but the time delays say it can be used with AC/DC voltage. They only cost 5 or 6 dollars. The one I have is rated for 18-30 volts. Do a search for Delay On Make Time delays 12VDC. I'm not sure if ICM makes one that will work for 12 VDC. Look for a small black box about 2in X 2in solid state delay. They make them with fixed timer or an adjustable time. I'd go with a adjustable since you want it to close a few seconds after the siren goes off. I'm sure you will probably find something else, but this will work for you. They are meant to be used for control voltage only, so you will have to add a relay.

Posted By: 704acc
Date Posted: March 02, 2005 at 12:18 AM

Derek, you went WAY over my head!  I have zero experience or knowledge of resistors and capacitors  {but I have relays and diodes down pat!}

Could you put it in layman's terms for me?

Radkonn, I will do a little searching as you suggested

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Ray Kane

Posted By: slush
Date Posted: March 02, 2005 at 1:47 AM

haha.. sorry...

https://www.tpub.com/neets/book2/3d.htm

Basically if you put a resistor in series with a capacitor, when you send a pulse to that little circuit, it will delay that pulse by the amount of time formulated by that equation i gave you.

I don't know how much delay you're looking for (in seconds), but you can still use that equation.  Just make sure to use a large (47uF would be fine) capacitor so you can have a good-sized delay.

Most places (radioshack... local parts stores) should sell ceramic and electrolytic capactiors.  Electrolytic are better.  You can probably pick up a 47uF 50V Electrolytic capacitor for something like 80 cents.  The resistor would probably be around a dollar for a pack of 10 10K (or whatever resistance you want to use.. the higher the resistor's value... the longer the delay).

If you want to calculate for a given amount of time, lets say, 2second delay (assuming you use a 47uF capacitor):

2s = R * 47uF

R = 2s / 47uF

R = 2 / (47x10^-6) ~= 42K resistor (radioshack sells 33K resistors and 10K resistors, so you could buy one of each and just put them in series... that would make a total resistance of 43K going into the capacitor... which is a little over 2s).

By the way, If i remember correctly, there are relays with built in delays...

-Derek

Posted By: slush
Date Posted: March 02, 2005 at 1:54 AM

Oh, and just a quick run down of what capacitors and resistors do:

capacitors store a charge

resistors limit the flow of electric current

Therefore the RC time constant sort of works like filling up a glass of water.  If you put your faucet on full blast it will fill up the glass (our capacitor) really quick (lets say, .5 seconds).  However, if you LIMIT that flow of water by turning the knob (knob limits the flow of water just like a resistor limits the flow of electric current.. so in this case our  knob is a resistor) your "glass" will fill up much slower, taking a  longer time to get charged.

Once a capacitor reaches it's charged level, it discharges its stored charge gradually.

Hope this helps.

-Derek

Posted By: 704acc
Date Posted: March 02, 2005 at 5:32 PM

Do you know where I might get one of these relays with a 1 to 3 second delay?I think I am catching on here - please correct me where appropriate:

Capacitors have a polarity and resistors do not?

I connect the switched 12volt+ siren lead to either side of a {what value?} resistor{s}

Then connect the remaining resistor lead to the positive side of a {47uF?} capacitor

Then connect the negative side of the capacitor to the relay's contact {85 or 86 - does it matter?} and the other relay contact to ground.

How am I doing?

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Ray Kane

Date Posted: March 02, 2005 at 7:37 PM

I think your better off buying a time delay... It's worth the money. They are easy to hook up.

Posted By: steiny83
Date Posted: March 02, 2005 at 7:58 PM
Perhaps you could use the horn output somehow.  On my Scytek Galaxy alarm, the horn output only sends a signal when the alarm goes off (not when the alarm is armed/disarmed).  You could possibly hook that output to your relay..?

Posted By: 704acc
Date Posted: March 02, 2005 at 8:34 PM

I think your better off buying a time delay... It's worth the money. They are easy to hook up.

I would rather buy a time delay if I could find one.  The places I called wanted a minimum of \$75 for what I wanted.  Any suggestions on where I could find a 12 volt dc time delay or a relay with a built in time delay?  I will also check on alternative ouputs from my Viper alarm.

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Ray Kane

Date Posted: March 02, 2005 at 10:49 PM

If it was seventy five dollars than it isn't the one I'm talking about. I saw one on ebay yesterday, but it was for 18 to 30 volts. There was a guy on ebay selling 10 delay on break time delays for like 15 dollars a while back. However, you need a delay on make time delay. I'll try and find one searching the internet. You can try doing it other way using capacitors and resistors; I was just trying to give you an easier solution. The time delay I'm talking about has regular 1/4 in stake on terminals.

Posted By: 704acc
Date Posted: March 02, 2005 at 10:56 PM
I really appreciate everyone's efforts.  If you do find anything please let me know.  I found a company called Kussmaul Electronics out of New York who has a time delay relay model # 091-100-012-B which might work.  What do you think?

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Ray Kane

Date Posted: March 02, 2005 at 11:22 PM

I did a quick search and found this one that has a .01 to 10 second delay. It is a little more than I am used to paying, but it should work if your willing to pay the price. I'd just try looking through some more websites. I hit this one on the second site I looked through. I just typed in automotive time delay into google. You can try some variations like 12vdc delay on make time delay, 12volt time delay, etc....

Hope this helps.

Delay On Make Time Delay

Posted By: slush
Date Posted: March 03, 2005 at 2:35 AM

704acc wrote:

Do you know where I might get one of these relays with a 1 to 3 second delay?I think I am catching on here - please correct me where appropriate:

Capacitors have a polarity and resistors do not?

I connect the switched 12volt+ siren lead to either side of a {what value?} resistor{s}

Then connect the remaining resistor lead to the positive side of a {47uF?} capacitor

Then connect the negative side of the capacitor to the relay's contact {85 or 86 - does it matter?} and the other relay contact to ground.

How am I doing?

Yes, that's right!  The type of resistor depends on the amount of delay you want.  The higher the resistance, the more delay you'll get.  Like my previous calculation, about 2s delay with a 47uF capacitor would require a ~42K resistor.  So you could do any combination (just simple addition of resistor values):

10K + 10K + 10K + 10K = 40K resistance (prob like 1.8s delay).

33K + 10K + 1K = 44K resistance (2s delay)

etc.

I don't know all of the resistor values that are out there... just those.  So if there is one closer to 44K or 50K you could get that and have a 2s-2.5s delay so you won't have to have a "resistor chain".  You would just connect each resistor to each other in series like:

TRIGGER----[ R ]----[ R ]---[ R ]--------|C(------RELAY

R = resistor, C= Capacitor.

Oh and remember, never reverse the polarity on a capacitor.  It's a nice way to see an 80 cent fire cracker (it'll blow up).  Just make sure the NEGATIVE side is going to the relay and you'll be good to go (the negative terminal is almost always marked on the body).

You could go the route that radkonn suggested, but you'd be spending around \$20 more than just getting these few parts from radioshack.

Just buy a very very small project breadboard, the 47uF capacitor, the resistor(s), a couple of wires, and you'll be set.

-Derek

Posted By: riceman
Date Posted: March 03, 2005 at 3:35 PM
704acc wrote:

This is my first post so please bear with me.  I am using the 12 volt positive siren lead from my Viper alarm to trip a relay in addition to powering the siren.  I do not want to energize the relay when the alarm is armed/disarmed and the siren chirps, but I want the relay energized when the alarm is tripped and the siren is sounding.  Is there a way to delay the current to the relay {but not the siren} for a second or two?  I have a JPEG of the diagram if anyone can assist me with posting it.

Regards,

Just a quick thought, now that you've hooked up your siren check if your alarm has a horn output wire sometimes the horn output wire on some alarms only trigger when fully triggered. On most alarms its a BROWN / white. hopefully that helps.

Posted By: 704acc
Date Posted: March 03, 2005 at 7:19 PM
Thanks to everyone for their suggestions.  I just went thru the installation manual - no such luck.  There is not an output for when the alarm has been triggered.  I am gonna keep the search up for some sort of delay.  If anyone runs across something, let me know

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Ray Kane

Posted By: zzimerclan
Date Posted: March 03, 2005 at 9:37 PM

Posted By: 704acc
Date Posted: March 23, 2005 at 1:00 AM

Well I purchased the DEI 528T pulse timer and started playing with it last night .  PLEASE SEE MY NEW POST

I need all of the help I can get!

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Ray Kane

Posted By: 704acc
Date Posted: March 24, 2005 at 7:04 AM

Any other ideas?

dare_ds69 wrote:

you can't

QUOTE=704acc]

 I purchased a DEI 528T pulse timer for my alarm.  I need it to wait a few seconds before providing power {via its built in relay or I could add a relay} to a second siren.  This will prevent the second siren from chirping on arm/disarm but have it sound when the alarm is tripped.  I am bench testing the unit before i install it.  The unit does the opposite of what I want it to do.  When the unit is triggered by a pulse from the "alram siren" the timer latches the relay for the set time then unlatches.  The wiring is as follows:  Red = 12 constant pos; Black = ground;  Black stripe = trigger wire;  Yellow = common 30;  Brown = normally open 87;  Orange = normally closed 87ahow do I get the unit to delay before latching?

[/QUOTE]

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Ray Kane