Electronic – Is RFID the right solution

• VOLTAGES USED IN THIS CONCEPT ARE LETHAL.

• ZAPPERS CAN KILL THE EXPERIMENTER.

• EVEN A SMALL CAMERA FLASH CAN KILL AND

• ADDING LARGER CAPACITORS AND/OR HIGHER VOLTAGES CAN KILL YOU EVEN MORE! (Being dead once is more than enough)

It's doubtful whether this query well matched to the aims of this forum.

The schema shown shows the general principle but nothing more. It's OK if that is its aim.

The cited web page is not technically competent.

The statement "Although we doubt that it has the capacity to cause any trouble aboard an airplane" is an alarming one given the intended aim of the equipment is to produce "a strong shock of energy comparable with an EMP". If taking such equipment onboard an aircraft resulted in the carrier being arrested nobody should be too surprised.

Specific questions:

1. This shows a basic lack of understanding of what you are dealing with. Direct connection of an HV cap to a supply will place a substantial load on the supply. The supply needs to be designed o deal with the inrush current or the inrush current needs to be designed o be limited. "Just doing it" is liable to cause damage.

2. It's not obvious why knowing discharge time is important in this context, but while designing, an oscilloscope works wonders. A voltmeter may be useful but far less so. If the circuit has high L & C and little R it may oscillate for a long time.

3. Can't tell. Read article you cite. Efficacy decreases with square of distance at short ranges. With cube of distance at longer ranges. Some RFID tags are liable to be destroyed at short range. As range increases it depends on how effective your coils is and coupling between coils.

4. A battery powered high voltage source is what is provided by a camera flash - so, yes, obviously. This is called in general terms, a boost converter.

It would be relatively easy to make a tag which was immune to such a zapper.

It would be easy to make a device which detected when such a unit was being used.

IANAL. Operation of such a device may make you liable for destruction of property charges. Generally speaking the cost of being found guilty of such a charge is disproportionately high compared to cost of damage done.

Attack defense:

If I told me then you'd have to kill me :-).

But, as long as you know the sort of attack you have to face you can always defend against it. The only issue is all up system cost - at some point you detect and use a Phalanx gun* on the offenders as a cheaper option :-). (* no - that noise is not a buzz saw). In real life a Phalanx liketargeting camera could identify zappers and other "persons of interest).

For starters, tags are alwayss resonant to increase volage and thus range and power transfer capability. (See Microchip AN710). Q factor (effective voltage multiplication factor) is typically in the range of 50 to 100. It would be simple and low cost for a tag to detect gross overrvoltage and to de-Q the circuit for a selected period. Just placing a short across the inductor will do this very nicely. You now have a straight transformer with Vout down by a factor of say 50 times. As power = V^2/R you may need as much as 2500 times the power level to get this back to as it was before. But maybe only 50x depending on various factors. This de-Qing would be cheap and easy to implement in an RFID transceiver or RX IC and if zapping became common you could expect this to appear as of right. If this is not enough you can consider getting creative with your inductor such that if voltage across half of it gets above some target level then the two halves are switched into anti-phase and cancel each other out. This is nicish as it means you are not trying to sink large amounts of energy and the high voltage levels appear at the coil and not at the IC.

The switches in such a system could be something like those in a Marx generator where they break down under over-voltage and act as switch elements and stay conducting until current drops below a certain level. This could be implemented with a few transistors and resistors forming an SCR or TRIAC structure so would be cheap easy and low area to implement. It wouldn't happen overnight but if the threat was concerted it would, or something similar. Or a Phalanx gun :-).

Marx generator working - the arcs al the way up the middle are switches! formed by an airgap designed to flashover. Replace this with an SCR and you get the same result.

Dont try this at home - use a camera instead.

We actually did a lot of research on implementing a system like this for our elderly customers. The problem with any tag based system is the same problem with any PERS system (I've fallen etc...). The problem is most people just won't wear the tags / monitoring bracelets. The closest thing we came up that might work would be having the family sew small tags into all their pants, or using the small space in a nike shoe where they keep their Nike+ hardware to store a xcvr. We also looked into using watches, but what we needed were nice metal watches not the plastic timex style ones that were available with xcvrs in them. Oh and there was talk of planting something in walkers and canes, if someone needs that to get around you could do it I guess.

There were plenty of meetings with talk about "social contracts" between the eldery caree and the caregiver where they would agree to use the tags but it was BS because the elderly were just not interested.

In the end we settled on a more complicated version of what you describe. Motion sensors throughout the house that communicate to our backend servers. There we process daily living patterns to determine if anything might be up. Has no one opened the fridge at 8AM, bathroom not used in last 4 hours but should have been, etc. Combining multiple sources seemed the way to go.

However that wasn't even the final solution for our customers. The expense of installing and configuring all those sensors is a pain in the... So our final solution is a touch screen system that the elderly use to check in on every day. The software and UI was designed specifically for an elderly user, and has things to check on medicine usage, are they ok. But it also implements a family section as well, with pictures, games, activities, video chat, email, web and a lot more. All designed for elederly non computer users.

This ended up engaging the elderly person a lot more, and we were able to take all of that information into our backend where the family or pro caregiver could see how they were doing. If someone fell we might not know right away but we'd know when they missed their next checkin. So not exactly what you're asking for but I thought I'd share our experience and see if it helped you out.