suggestions for setting up a dosimeter charging system

If you want to make the charger stationary, it is simply a matter of delivering the proper DC voltage - which I dimly remember is supplied by one D-sized cell in the container. And as these were based on conventional Leclanche cells, that would be 1.56 volts DC. That should not be too difficult. But, of course, you would need some power from some source. That, sadly, is the nature of those beasts.

Peter Wieck Melrose Park, PA

Totally off-the-wall suggestion. Is there any way that a piezoelectric gas lighter could be used or modified to charge the dosimeter? No batteries required and only a dollar or two to buy.

With that in mind, how about one of those anti-static devices for records?

Bit pricey, however.

Peter Wieck Melrose Park, PA

No, I'm trying to get away from having to use the battery. Something like a crank generator. The original Bendix model from the 50's had such a generator built in. It is 1.5VDC, yes and a single D cell.

I believe my hand trigger charger has such an element in it. It's not like a lighter that has an instant trigger mechanism, but more like the Zerostat unit, so a gradual charging, depending on how fast or slow the trigger is pulled.

I wish such a piezo element was available as a part somewhere, but I have been unable to locate one. When I was a kid, I actually had a unit like the Zerostat that my dad picked up for me at a surplus place. It must have been thrown out years ago because I haven't see it since adulthood.

I don't have a suggestion, but I am curious - what use has your relative found for the dosimeters? I have one without a charger, but it was charged when I received it and has barely discharged in the many years that I have owned it, and I hope it never will (or not when I am near it anyway!) Its full-scale reading is a fairly decent fraction of a lethal dose IIRC.

It's ok, I've been asked that before. Well, with things being what they are in the world lately, I've been trying to set up not only myself, but a relative or two as well with some radiation monitoring systems. The idea with the pens and chargers is that, in the awful event a large scale nuclear event occurs, that we might increase our chances of survival. As I write I doubt that our odds would be that get to even get to the point of monitoring (we are all within 50 miles of major cities and military bases), but just as a precaution. I have seen all of this CD equipment for years and decided to go with a bunch of the pens and chargers in a trade. Something high level is definitely needed because most "geiger counters" would be useless after such an event. We all have geiger counters, but I doubt any of them would even survive an EMP. I have some low range pens as well, only up to the 200 mR range that might come in handy for less severe events, such as atomic plant incidents. Oh well, these are just some ideas and precautions that have cost next to nothing to try implementing. I don't really trust that batteries would be all that reliable after a crisis, which was why I was looking for a non-powered way to allow the 1.5V chargers to still work.

OK - Let us address each concern in turn:

Battery reliability: Solar cells come immediately to mind. It would not take many, and you could set up for the current you need. Install with a rechargeable, and you are all set.

EMP: Those little CD Geiger counters are both incredibly simple and designed for survival. The mil-spec. ones are even better that way. A larger concern would be whether the counter could give you meaningful readings for Alpha and Beta particles - mostly harmful only if the producing materials were ingested or inhaled. Gamma radiation can be detected in any number of simple ways, no batteries needed.

Dosimeters: Those dosimeters will be useful only if you *know* there is a danger, and therefore pay attention to them, not so much that they indicate (they will), but the period of time it takes them to indicate. Note that they are useless for Alpha and Beta particles, as they are too well shielded. A piece of heavy aluminum foil is sufficient shielding for either - but for the inhalation issue.

Survival: No modern medication, including statins, blood pressure medicine, epi-pens, antibiotics, vaccinations, nor any other infrastructure-dependent materials after the immediately existing supply is used up. Note that these materials have a relatively short shelf-life, so stockpiling is impractical. Then it gets down to supermarkets, transportation, human predators and the other wonders associated with a collapsed civilization. If your survival is based on a FBO, you will be subject to siege - and that is 100% a losing battle, 100% of the time. History has proven that over and over. And if you are nomads, fuel (vehicles) or food (animals) become a serious issue. As well as being highly visible and high-value targets.

Best to work towards preventing Armageddon, rather than preparing for it. Spend that energy on something more joyful than the collapse of civilization.

Nuclear Plant Accidents: See electroscope above. If there is enough ionizing radiation released to do you harm, that little device will indicate pretty much instantly. Meaning that you will have to 'get out' along with everyone else, and have somewhere to go. At which point, only a Chernobyl-level event is any real threat outside of that 'magic' 10-mile perimeter, or 20 miles +/- downwind.

NOTE: We keep a mil.-spec. Geiger counter, as in the past, my wife was fond of Fiesta Ware, some colors of which are radioactive. Not so as to be harmful, but one does not wish to eat from them. And before the hospital I work beside closed down in 2019, the radiation-safety people wore dosimeters routinely as they worked around radioactive materials used for cancer treatments.

Peter Wieck Melrose Park, PA

If a hand clank generator is acceptable, then a hand crank cell phone charger should be a good starting point. Plenty to choose from:

I have set of 4 dosimeters and a CD V-750 reader. I made the mistake of storing them with D size alkaline cells installed. The alkaline cells all leaked and did quite a bit of damage. Anything you can do to eliminate alkaline cells is probably a good idea. For the matching CD-V500 Geiger counter, I simply installed a 14500 LiIon cell (with a

Doing something similar for the dosimeter reader is more difficult because of the lack of LSD (low self discharge) 1.5V cells. I'll probably need to build a LiIon 7.4v (two cells) to 1.5V buck inverter. Currently, I'm using a single Lithium cell:

One more hint. If you're really preparing for a full blown nuclear disaster, make sure that your equipment can operate in very high levels of radiation. Most equipment does not do well, will overload easily, and produce either no reading or a useless reading.

Thanks, fair enough.

I think you could rely on some Eneloop cells if you swap them for a freshly charged one every year or two. Check that the voltage is sufficient if the device was designed for 1.5V. Alkalikes would also do if you could find good ones, but ones made in the last few years seem to leak.

People, too...

As I understand it, that's the reason that most of the radiation survey meters in the old Civil Defense kits were ionization-chamber types. They cover ranges of radiation which are actually harmful or lethal to humans in a relatively short amount of time (minutes to weeks). They're "no, you really don't want to be here, get the hell away" devices, just like the dosimeters.

They don't respond well to low levels of radiation (background, NORM, uranium glass, Fiesta ware, etc.).

Their biggest disadvantage is that they operate at such high impedances (to measure leakage in the ionization chamber) that they're very sensitive to moisture. As I recall, they're supposed to be "baked" periodically to make sure they're dry, and then stored sealed in plastic with a dessicant pack.

The old Civil Defense kits tended to come with a bunch of these ionization meters, some dosimeters and chargers for them, and one Geiger counter. The Geiger was intended more as a training device than as an actual "when the bombs drop" tool, due to the problem you mention... in an actual fallout zone, Geiger counters and scintillation detectors will probably saturate and read low or zero.

Which is why we have a mil.spec. counter with an "alpha-detector" window - an area of very thin material that may be exposed by twisting a cover on the head. And a small side-detector as well.

Peter Wieck Melrose Park, PA

There are actually two similar looking boxes in the kit. (I can provide a photo of the kit as soon as I find the box). The C DV-700 geiger counter, which uses a Geiger-Muller tube, and the CD V-715, which is an ionization chamber:

Yep. The entire range of the geiger counter on X100 is about 1/2 the first division of meter on the ionization chamber.

Nope. The ionization chamber is hermetically sealed (sealed by a hermit):

However, I have seen problems with the phenolic paper PCB used in most early units. The PCB absorbs enough moisture to cause high resistance shorts. A few minutes in a toaster oven usually solves the problem. If I see some flux left on the PCB from a previous repair, I clean it off with water and alcohol separately, and then coat the area with some manner of conformal coating or high-voltage corona dope.

Today, methinks that some of the higher end radiation survey meters have an PIN diode gamma ray detector for the higher doses:

Yup... or, at the very least, that you're likely to be radiation-sick for some time.

Even though the chamber itself is sealed, there can be leakage problems if condensation builds up on the area where the probe wire comes out through the glass seal. That insulator, and the high-megohm resistors and the ceramic switch assembly are (according to the manual) all part of the high-impedance circuit. Any contamination here causes problems, and I've seen condensation have that effect as well.

I think your approach of an alcohol cleaning, and then good high-Z conformal coating is probably just the ticket. And, yeah, phenolic- paper PCBs are rather on the loathsome side, for a bunch of reasons :-)

I've got an old one of these sitting around in a closet. I've been thinking of turning it into something more useful by gutting it, and replacing the ion-chamber system with a small PMT and a plastic scintillation crystal. It still wouldn't be of any real use in a high-fallout zone but it could make a nice, sensitive survey meter for looking for NORM of one sort or another.

Also, you use the CMOS sensor in a smartphone as a radiation detector: "The suitability of smartphone camera sensors for detecting radiation"

You can also obtain organic plastic scintillating slabs: