special application relay

I need to change a constant negative to a momentary negative.

I found a diagram on this site to change a constant positive to a momentary positive  www.the12volt.com/relays/page5.asp

Is there a simpler way to do this other than adding another relay to the momentary positive output to switch it to negative?

I am also unsure whether this diagram shows a diode.  It looks like one, but isn't noted in the description.

www.the12volt.com/relays/relays.asp describes why this might be necessary, but I'm not sure

I think, maybe I'm a dumbass.  I just have to make 87 a ground to get a momentary ground output from 30.

I installed a Clifford Avant Guard 4 alarm on my work van.  It has the ability to autostart for low temp and/or low voltage.  This option has to be remote activated each time I disarm and rearm.  This is a hassle, for instance, in the summer every time I run out to the truck for a tool it's one button to arm two buttons to vent the windows and two buttons to activate voltage/temp.

So I got an external time temp controller thats a little more use friendly.  The controls would be right on the dash, it's settings are more flexible, its back lit.

I've since realized that I have no way to connect this to the alarm.  The time temp controller has a momentary negative trigger.  The remote start trigger goes from the alarm unit to the remote start unit via a two wire bus line whether it's due to voltage, temp or remote control.  How information is sent back and forth between the two is beyond me. It's certainly not a positive or negative pulse.

So I was about to give up when I got the bright idea to use the negative trigger on the time temp unit to energize a relay that would be hard wired to the auto start button on the companion remote I got with the alarm.  I think the weak point in this setup is having to occasionaly change the battery in the remote

Now that I've convinced myself this might work I figure I could do the same with a voltage monitor

The output I'm dealing with is an internal relay on a low voltage alarm.  I have N.O., N.C. and COM contacts.  I can have a negative or positive output.

When voltage drops below 11.8 volts for 120 seconds, the relay is energized until the voltage rises above 12.8 volts.

I'm calling this a constant output. I guess its not really but its much longer than I need. I think it would take a minute or two for this internal relay to switch off.

I only need a momentary trigger and I'm relying on a small battery in the remote that I don't want connected for a minute or two.

So, I've got a constant output of my choice that needs to end up a momentary negative trigger.

Can I turn a constant negative into a momentary negative?  I would rather do that than use a constant positve to get a momentary negative.  Hopefully its as easy or easier.

thanks,

Jonathan

Jonathan, I described in my post above how to convert your 120 second negative ouput to a momentary ouput by rewiring the relay configured here: https://www.the12volt.com/relays/page5.asp#ctm , connect the ground shown going to the cap and resistor to your constant negative output, connect 86 to a constant 12V+  source, connect 87 to ground, and 30 will be your momentary ground output. 

For this configuration, the constant 12V+ is needed only for the coil of the relay to energize. If you had a positive output, the constant 12V+ would not be needed to get the pulsed ground output you're after.

the12volt