A nifty hack on making a modern GM counter

[Richard Hull]

As some of you might know I have now been retired for 1 full year. Recently I have been working with the Arduino and have for many years assembled my own radiation measuring gear. I have repaired many older instruments and have a vast collection of cool older stuff that, for the most part, is fully functional.

I have been selling GM counter kits and individual components at hamfests for about 8 months. Fukushima really helped sales to the easily duped and buck ignorant RAD hating "fraidy cats". Tacitus in his histories said of such blind believers upon seeing them cast coins into a collection basket after being tricked by a supposed miracle........."an adroit man of the world would soon have his fortune made if cast among them"

Well, I submit some interesting images of a recent project that is effectively complete with future modifications in the works and allowing of easily alterable software upgrades.

My new toy is a GM counter with a brain. The $500.00+ "Inspector" was my general inspiration with the idea of holding list prices down. to about 1/2 or less of that figure. I have also worked out a much smaller box that can be an attached add on to give the CDV 700 "tin-man" a brain with virtually little of no modification.

My counter's menu asks whether you want gamma data or beta data. Then, it querys whether you want roam or laboratory mode. If roaming, do you want the CPM alert sounded once that cpm is exceeded? If in lab mode do you want a timed count and then a full data report or do you wish a specific count to stop at and then issue a data report? The continuous display during all modes shows the averaged CPM data taken over a 6 second interval along with the elapsed time and total count to this point. I imagine this will work out to a continuing work in progress over time.

One of the key issues was low power consumption and long lasting power to the portable instrument. The finished item draws 71ma at approx 8 volts from a lithium-ion battery. I have been to the Raliegh hamfest last weekend and bought a ton of cool lithium batteries. All were brand new and I have tested most of them. I got all in the image for $30.00. Great Hamfest!

Also some images of me in the development area.

The images are self-explanitory to the marginally informed in electronics and basic radiation instrumentation.

Click on the images to enlarge.

Richard Hull

[Steven Sesselmann]

Richard,

Nice project, looks like a very neat assembly.

Love that desk lamp you have too.

Steven

[Richard Hull]

Thanks Steven.

The desk lamp is a 120v 60W eqivalent 13W Phillips LED light that is a nice odd flat shape. (found at a local Home Depot) I manufactured the assembly to slide in and out of the overhead instrument panel on rails as needed to work on various projects.

Making a working electronic development area "human friendly" is very important as you will spend hours at it. Mine is a U shaped benched area with room for only one person in a swivel chair so that all three bench areas are easily accessable with a mere swivel in the chair. I use the U shaped bench theme in my outside lab as well. A good use of space and I believe you can never have enough bench top.

Richard Hull

[Jerry Biehler]

What are you using for a controller ic for the LiPo?

[Richard Hull]

There is no controller IC for the LIPO in my counter. If, however you are speaking of charging issues, the lithium-ion terminals are brought out the back and I have a $140.00 special charger for lithum Ion batts. I am sort of big into the technology so I am armed with a more than adequate charger/balancer. Most Lithium ion batteries of some energy, (computer batts, camera batts, etc.), have internal controller/balancers. The term LIPO is a common usage for lithium ion batteries. there are, in effect no real lithium polymer batteries in common use. It is effectively a failed technology that gets picked up for development often, but never makes a splash in the consumer area.

Lipo is a term first spread about and continues to be used in the Hobby R/C world in which the bulk of the chatter regarding their lithium ion batteries relates to online and in the public arena. R/C batts almost never contain a controller balancer. This allows the user to draw over 50 times the rated mAh for short periods common to the hobby without damaging the battery. A typical internal controller as found in high energy consumer apps would not allow that. This is why the absolute best and most expensive charger/balancers are aimed at the hobby market, as it is critical to pamper such short term use, ultra high drain app batteries at recharge time to keep them in good order.

My charger/balancer seems to have about two different contollers and about 100+ other IC's and passive components on its circuit board. It is selectable for 1 to 5 cells and within that range separately selectable from 300 to 3600mah to closely match the battery/batteries in the charging effort. As in all such special Lithium-Ion chargers there is no capability of hooking it to the AC mains. Instead the manufacturer forces you to charge from a car battery power source (out of the car and out of doors) This is to prevent setting your house, shed, or car on fire.

I could go on and on regarding this topic, but suffice it to say these are the batteries of the future, yet still demand careful and special efforts to keep the consumer and his property safe when they are used. Each new generation of Li-ion chemistry gets safer, though the highest energy density chemistry batts remain dicey and require a bit of TLC. As in any battery type there are trade-offs.

Richard Hull

[Richard Hull]

The one battery chemistry I refuse to use and leave in any portable device is alkaline batteries. I have taken a bold, giant leap backwards to carbon-zinc batteries in all flashlights and radios where individual 1.5 volt cells are demanded.

Alkalines exhude a vapor, no matter how well sealed, and ultimately they drool a chemical that destroys, in rather short order, all manner of contacts in a device. The signature is a light blue powder and corrosion all over and around the sets of contacts. I have new unused packs of both Mallory duracell and Everready alkaline batteries. After about two years, all the packs of alkaline type have one or more batteries oozing and the cardboard boox has a white powder in it. All of my Harbor freight, chi-com, carbon zincs of the same age are good to go.

Of a particular rotten nature are the alkaline 9 volt transitor radio type batteries. Again, one of the 6 cells will leak and ruin the entire battery with the other cells all still in good shape. The very best of these bateries are connected via spot welded ribbon, but of late, many are going to pressure plated contacts on the battery's cardboard end plates and these are the real pits!! They fail easy and fast. More bread for the manufacturers, planned obselescence.

If you are going camping and will use your batteries heavily and often, alkalines are fine, but remove them all once home. They have great power reserves, but terrible in device storage reputation where I am concerned.

Nickel metal hydride and lithium ion are really nice, but demand special charging proceedures. Nickel metal hydride suffers from too low a voltage to replace common 1.5 volt batteries and Lithium ion are far to high in voltage for direct drop ins. Both are special app types for portable devices.

Richard Hull