Battery switch activation via security system?

[mkassab]

Need some advice/confirmation on what I want to do with my Cobra Electrical system. Pls refer to the attached electrical diagram (in particular, the lower right hand corner).

Background: I will not have a keyed start option. I’ll have a on/off switch for ACC and Ignition On and a start button. For security, I’ll have a remote battery switch that’s activated electronically when you supply a ground to it (i.e., no manual key to turn on). I will also install a Viper 5901 security system.

Plan: I want to add a simple standard relay switch to the remote battery switch to supply the ground to it to supply power to the car. I want to activate the relay with a negative input from the Viper security system. When the Viper is disarmed, it can provide a Aux/trunk 200mA negative output. I’d connect this output to the relay. This in turn would provide a higher amp negative output to the battery switch. The battery switch is the Painless # 30204 (http://www.summitracing.com/parts/PRF-30204/ (http://www.summitracing.com/parts/PRF-30204/) ). It came with a toggle switch to supply the ground… but obviously, this is not a secure option… therefore why I added the relay and connection to my security system. Not knowing the amp draw on the battery switch negative/ground activation, I’m playing it safe by adding the relay for the ground.

So, my question to those that understand electronics…. Do you believe the 200mA negative output from the security system will work OK to supply the ground to the reply switch to activate it and therefore offer a good ground to the battery switch to cause it to active?

If you need any further clarification…. Pls ask.

Thanks to all in advance…. Mark

[Jim Harding]

Mark, not knowing the voltage/current requirements of the relay's coil in question, I'd take my multimeter and measure the current while testing the relay with a 12 volt battery on the work bench. If it draws less than 200 mills, you're good to go. But, if 200 mills is max for the security system, I'd try to locate a relay that would draw a lot less (less than 100 mills) so as not to stress the security system. The next thing to know is how much current will that relays contacts handle. This is something that you'll have to know too. It has to handle the current requirements of the battery relay. I checked the link for the Painless battery switch to see how much juice it needs to close in, but there was no info for it. But again, this is easy to do on the bench with a multimeter and a 12 volt battery. Do you know for sure that the security system can't drive the battery switch directly?

- Jim -

[mkassab]

Jim, thanks for your comments. The battery switch itself can handle 250 amp load (peak 2500 amps) as you saw on the link I provided. The relay for the switch isn't specified. I'll do what you suggest and run some test, but I'd sure hope my 30 Amp relay would be way more than enough. Your last comment.... ” Do you know for sure that the security system can't drive the battery switch directly?" Answer, no I do not know,,,, that's why I was playing it safe sticking a 30 amp relay between the Battery switch/relay and the security system to make the ground for the battery switch's built in relay. Mark

[mkassab]

Mark,
I think you are fine with what you have planned. But, here are the details, plus one suggested upgrade and one question:

Like you, I didn't find the pull-in/coil current requirement for your "remote battery switch" - which is obviously just a high-current relay. Probably something like the standard Ford one mounted on the fender of billions of their old vehicles. In any event, the coil current obviously can't exceed the capacity of the toggle switch they supply, and most such switches are rated at 20 amps or less at 14 VDC.
The "Bosch" relay (apparently Bosch came up with it eons ago and the name has stuck) that I assume you'll be using, like this one (http://www.parts-express.com/pe/showdetl.cfm?partnumber=330-070&source=googleps (http://www.parts-express.com/pe/showdetl.cfm?partnumber=330-070&source=googleps)), has a rating of 20 to 40 amps - depending on which one you buy. So, it is easily able to handle the current for the remote battery switch.
Also, the typical Bosch relay needs 150 - 160 ma (.15 - .16 amp) through the coil to pull in. So, your security system should be able to pull the relay in since it can sink 200 ma. But, you might want to make sure the relay you buy does only need ~150 ma.
The suggestion: If it were me I would put a diode in the coil circuit as shown here: http://www.techimo.com/forum/general-tech-discussion/180227-where-do-i-install-protection-diode-relay.html (http://www.techimo.com/forum/general-tech-discussion/180227-where-do-i-install-protection-diode-relay.html) As discussed in that thread, the diode short-circuits the spike of voltage that occurs when the relay drops out. That spike can go to several hundred volts and might damage your security system - although I'd bet they have it protected against such possibilities. Still, I would do it and I'd put the diode in the wiring harness as close to the relay as reasonable. That way that voltage is taken out before it goes down the wires and influences any other nearby wires/circuits. As for what diode, the typical one used is a 1N4148, although about any fast switching one that can briefly handle ~1 amp will do.
The question: Do you know that the security system is happy sinking ~150 ma through its Aux output for long periods of time? If you haven't, and knowing you I'd bet you have, you may want to call Viper and confirm that. You wouldn't want it to overheat and quit when you've driven several hundred miles from home.

Looking good,
Gary

[Jim Harding]

Your last comment.... ” Do you know for sure that the security system can't drive the battery switch directly?" Answer, no I do not know,,,, that's why I was playing it safe sticking a 30 amp relay between the Battery switch/relay and the security system to make the ground for the battery switch's built in relay. Mark

Yeah, I just looked up some papers I have here and that solenoid will need more than 200 mills. I also checked some run of the mill auto relays that I have in the shop and they draw from 150 to 170 mills. If what you have draws something similar, let me know and I'll spec out a transistor switch that will do the job for you and not stress the security device.

- Jim -

[mkassab]

The question: Do you know that the security system is happy sinking ~150 ma through its Aux output for long periods of time? If you haven't, and knowing you I'd bet you have, you may want to call Viper and confirm that. You wouldn't want it to overheat and quit when you've driven several hundred miles from home.

Looking good,
Gary


Gary… thanks. I do not know the answer to your question…. And I’ll find out. I’ll add the diode. As a precaution, I’ll add a “Hidden” switch (the one that came with it) between the relay I’ll add and the Battery sw and just leave in off position. If I turn it on, it will ground to the frame.

All your other points are spot on!!!

Thanks Mark

[mkassab]

Yeah, I just looked up some papers I have here and that solenoid will need more than 200 mills. I also checked some run of the mill auto relays that I have in the shop and they draw from 150 to 170 mills. If what you have draws something similar, let me know and I'll spec out a transistor switch that will do the job for you and not stress the security device.

- Jim -


Jim, thanks a lot !!! I'll let you know.
Regards, Mark

[Slither]

Need some advice/confirmation on what I want to do with my Cobra Electrical system. Pls refer to the attached electrical diagram (in particular, the lower right hand corner).

Background: I will not have a keyed start option. I’ll have a on/off switch for ACC and Ignition On and a start button. For security, I’ll have a remote battery switch that’s activated electronically when you supply a ground to it (i.e., no manual key to turn on). I will also install a Viper 5901 security system.

Plan: I want to add a simple standard relay switch to the remote battery switch to supply the ground to it to supply power to the car. I want to activate the relay with a negative input from the Viper security system. When the Viper is disarmed, it can provide a Aux/trunk 200mA negative output. I’d connect this output to the relay. This in turn would provide a higher amp negative output to the battery switch. The battery switch is the Painless # 30204 (http://www.summitracing.com/parts/PRF-30204/ (http://www.summitracing.com/parts/PRF-30204/) ). It came with a toggle switch to supply the ground… but obviously, this is not a secure option… therefore why I added the relay and connection to my security system. Not knowing the amp draw on the battery switch negative/ground activation, I’m playing it safe by adding the relay for the ground.

So, my question to those that understand electronics…. Do you believe the 200mA negative output from the security system will work OK to supply the ground to the reply switch to activate it and therefore offer a good ground to the battery switch to cause it to active?

If you need any further clarification…. Pls ask.

Thanks to all in advance…. Mark

Mark,

That 200mA Viper low-side-driver terminal will NOT hanldle the current load of the Painless 30204 solenoid. The 30204 has a nominal current draw of 2.5A to activate it. But, I'm not sure I like the idea of adding another series component that could fail, i.e. the extra relay, to the system, though it won't have any trouble sinking the current for the 30204.

If I'm not mistaken, the Viper has two higher-current outputs for ignition, i.e. it cuts out the vehicle's ignition system when armed. I do not know exactly what the continuous amperage load capabilities are of these outputs, but a quick call to Viper's tech support with an explanation of your intent should get you the info that you need to determine if the extra relay is needed.

Another posibility might be to use the switch that came with the 30204 as designed, and use the Viper to disable the ignition instead of the battery switch.

Regardless, Gary is spot on with the fly-back diode recommendation[thumb]!

One last thought... you might consider burying an emergency bypass switch deep in the bowels of the car... something that even you have trouble getting to... so that in the event that the Viper or your relay fails while you are out driving you can get the car back home.

Good luck!

[mkassab]

If I'm not mistaken, the Viper has two higher-current outputs for ignition, i.e. it cuts out the vehicle's ignition system when armed. I do not know exactly what the continuous amperage load capabilities are of these outputs, but a quick call to Viper's tech support with an explanation of your intent should get you the info that you need to determine if the extra relay is needed.

Paul, you are correct, the Viper puts out a (-) 500 mA ground as long as the system is armed for the ignition cut off. I was planning to use the ignition cut off in addition to the battery cut off... (if you look real hard in the upper left (I know ... it's small print) at my electrical diagram, you'll see the ignition cutoff. I was planning to install a "back door" to bypass the Painless remote Switch).

Mark

[Slither]

I was planning to install a "back door" to bypass the Painless remote Switch).

Mark

To be a real back door it should bypass the starter interrupt switch (Viper), as well...

Here is another thought:

What if you leave the 30204 as designed, and use the Viper to take out the starter switch as you have drawn and additionally disable the MSD box (or whatever you are using) as well... then the starter doesn't work and if they try to push it, neither does the ignition.

That alarm system isn't cheap... might as well let it earn its keep;).

Just a thought...

[mkassab]

What if you leave the 30204 as designed, and use the Viper to take out the starter switch as you have drawn and additionally disable the MSD box...

Paul, I like the MSD "Kill" So here's what I'm going to do...

1. Use my Painless Battery Sw via a relay as planned... but with a 5 pin relay (one that has post 87 and 87a outputs) Where 87a is the default relay switch connection when NOT activated. 87A will provide the ground to the Painless Battery sw. The Viper Security has a -500mA output when ARMED.... and will drive this relay to the Batt Sw. and therefore disconnect ground by switching from 87A to 87 (87 will not be connected to anything). This way, if the Viper dies, I have ground to the Batt Sw by default, therefore, pwr to the car. I’ll add the toggle switch that came with the Batt Sw between the relay and the batt sw as designed. Again, another way I can kill the Batt sw.

2. Viper disconnect of Starter
3. Viper disconnect of MSD Ignition box.

I'll still install the back door, carry extra relays and several male-to-male 1/4" spade couplers to bypass the relays if all else fails.

The Viper 5901 also has a long range feature in that the LCD remote FOB has up to a mile range and will monitor the security system and let you know of any activity. I just received the VSM100 Viper Smart Start option that adds cell network connection so I can access/control via my iPhone. This way, I can monitor the car anywhere I have cell connection and not need the FOB (the iPhone will lock/unlock, receive alerts, etc). Obviously I won't use the remote start feature... not much use in a open Cobra :D.

And, yes, I know this is all an overkill, but I can't help myself.... I love "gizmos and gadets". Over engineering isn't bad, is it? :confused:
Mark

[Slither]

Paul, I like the MSD "Kill" So here's what I'm going to do...

1. ... This way, if the Viper dies, I have ground to the Batt Sw by default, therefore, pwr to the car.

Mark

OK, I guess... as long as the Viper can't be bypassed by taking it out... the failsafe should probably be that the back door is needed on system failure, maintaining security so that crooks can't start the car by disabling the Viper.

Have you done a new schematic, yet?



And, yes, I know this is all an overkill, but I can't help myself.... I love "gizmos and gadets". Over engineering isn't bad, is it? :confused:
Mark

No, it is definitely not bad... just ask any engineer... oh you are asking an engineer:D! However, when you are stuck on the side of the road, having previously eliminated all unnecessary potential failure points is worth its weight in gold. Not having to troubleshoot something under adverse conditions is a really good thing.

When I think of over engineering I think of extra-robust designs that improve strength, fault-tolerance (i.e. in this case can still run under partial failure - back door), graceful degredation (i.e. a failure in one part does not take out/damage another part), etc. Extra complexity may not exactly fit these parameters;), but only you know what you need to have in the car.

Keep us posted[thumb]...

[mkassab]

Paul, No schematic, but working on it.? I appreciate your time and input. Will update shortly. Thanks Mark

[Tom Niebrand]

You may want to look at this product. They make some mechanical latching relay. This means in the close position no draaw on the battery. In the open position no draw on the battery. The only draw is when you change position to open or close position. This would make a good anti-theft. Just look at the battery guard products. www.intellitec.com (http://www.intellitec.com)

[mkassab]

Thanks Tom.... I'll check it out.
Mark