EMF and key FOB drain - possible?

[eurosteve]

Hi

I posted this odd question under "technical discussion" because my hope is that someone will seriously consider my situation and give a thoughtful response, rather than dismissing this out of hand. I'm hoping that some engineer type will consider this.

I have a two-way key fob for my wireless home alarm system (Ingrid) and I've just had my second one go bad in 2 months - since I got my Prius a little over 2 months ago. The symptom is battery drain to the point where it will only operate right next to the receiving console unit. ( I sent the original one back to the manufacturer and the same thing happened with the new one.) I posted on this 6 weeks or so ago when the first fob went bad and I thought maybe the Prius fob was somehow effecting the alarm fob. Now I'm wondering about whether the Electromagnetic field created within the Prius might somehow be effecting the fob. You all probably saw the recent article about EMF's created in the Prius - and that gave me this idea.

It is most likely that there is some sort of flaw within these key fobs and their demise has nothing to do with the Prius but - my wife also has one of these key fobs and it is doing fine - and she drives an Audi.

So what do you think, is it possible?

[ZC1]

My first inclination is: During FOB storage, either in your pocket, briefcase or wherever, one of the buttons is occasionally being held down.

I have a situation where I'm always hearing my car lock/unlock and arm/unarm because my car key FOB in my pocket is pressing something. I need to change it's default habits.

As a test, you could make no changes to how you store your home FOB, but rather, change your FOB battery then swap it with your wifes. Do that for a week or so, it may have something to do with you as opposed to the Prius itself.

The Prius cable voltage EMF is extremely low (which halves in power for each doubling of an equal distance) and I don't know that the Prius has any transmitters other than the Garage door opener (Homelink).

Try the FOB swap, see what happens.

ZC1

[Bill Merchant]

ZC1, the Prius has SKS transponders if the car is so equipped.

I'm a little confused, Steve, about which fob is failing, the Ingrid alarm fob or the Prius key fob? If it's the Ingrid fob, try replacing the battery, so you know it's fresh, and storing it in an Altoids tin when it's in your Prius. The tin box should provide sufficient shielding from any stray EMF or RF in the car.

I'm not familiar with the Ingrid system. Is it passive, like the Prius SKS system, so the security arms and disarms based on proximity, or do you have to press a button to actively change state? If it's active, there seems to be little chance that an external signal is somehow triggering it to be active and drain its battery, but putting it in a metal box to shield it won't hurt.

[eurosteve]

Thanks for you ideas. When the house alarm key fob failed the first time about 6 weeks ago, I replaced the battery and the unit didn't work with the new battery. It might have worked for the first few days, I've forgotten. I could replace the battery in this one and see what happens. And I could do the switch with my wife's fob to see what happens. I guess if the fob doesn't work with a fresh battery, then the issue isn't the battery at all...

Just to clarify, it's the Ingrid fob that fails. It requires you to press a button to activate or inactivate the alarm. BUT after you press the button to activate or inactive, the fob listens for a confirming response from the alarm system. The fob makes little beep sounds and the led flashes when you send the signal to the alarm system and when a return, confirmatory signal is received back from the alarm system. With that in mind, I wonder it the Prius keyless entry system is sending a signal to the Ingrid fob that is drawing some power. Along those same lines, could the EMF in the Prius (or the keyless entry) also influence the alarm through that listening mode (in the Ingrid fob) to draw down the power?

Thanks again for thinking this through with me...

[ZC1]

At least swaping the key fob with the wife may rule out or reveal a defective key fob and putting the home fob in an altoids tin while in the car may prove an EMF problem.
Never combine the tests, it makes the problem more vague.

I don't have the frequency information on the Prius SKS system.

[qbee42]

If the house fob requires a button push before activation it is not actively listening for a signal, in which case the Prius fob will not cause it to drain. The Prius fob is passive and does not radiate until it hears a signal, although it can confuse other RF as a signal from the car.

Are you hearing beeps from the house fob at random times?

Try trading your fob with your wife's fob, since hers is known to be good.

Tom

[jayman]

Wasn't there a known issue with the Prius SKS fob and Shell SpeedPass?

[efusco]

Originally Posted by jayman

Wasn't there a known issue with the Prius SKS fob and Shell SpeedPass?

Yea, I think they fixed it though as I've not seen a single mention of the issue since the early '04s.

[eurosteve]

I'm not hearing any activity from the Ingrid fob. I'll have to swap with my wife. This will confirm that something about being with me is causing a problem with the fob - rather than my having gotten 2 defective Ingrid fobs. Thanks for the ideas.

[tmanson]

I have a couple comments Steve.
I heard recently that keeping a cell phone in an RF-thight environment (like a metal filing cabinet or desk) will cause it to drain faster than normal because ti is always searching for its RF source. I don't know whether your Ingrid fob does this or not, but it might be worth consideration.

I can also imagine that a good test is separating the Ingrid from the Prius fob just to see if the battery in the Ingrid last longer (this may have already been discussed and I just missed it). It sounds like another good test is what you just proposed - trading with your wife to see if that makes a difference.

On the subject of acronyms (unrelated to the Ingrid drain problem): Years ago back in engineering school the term EMF stood for Electro-Motive Force (or voltage). Fields were more commonly referred to by other terms (flux etc.) and their impact on on their enviroment as EMI/EMC (Electro-magnetic Interference/Electro-Magnetic Compatability). However it appears that the recent advent of the metaphysicists (or whomever) have cause fields to be more well known and redefined EMF as the term you are using. It sure caught me by surprise. I guess I am getting too old.