higher geiger voltage on arduino geiger counter

can't find any information about the zener diode array on the arduino geiger board...my tube (d-22) takes about 800-900v and i cannot find any information on how to jack up the voltage from the original 500v setup. supposedly 1000v is obtainable but i cannot find anywhere information on how this is done- thanks/ radleb

The best way to do this is to change the transformer to one with a higher turns ratio. The other way is to feed the transformer primary with twice the input voltage. Make sure the HT capacitors can take the extra voltage.

radleb: can't find any information about the zener diode array on the arduino geiger board...my tube (d-22) takes about 800-900v and i cannot find any information on how to jack up the voltage from the original 500v setup. supposedly 1000v is obtainable but i cannot find anywhere information on how this is done- thanks/ radleb

Usually an "inverter" is used for this purpose. It's a transformer type power supply in reverse. That is, a low voltage DC circuit oscillates and sends low voltage AC to a small transformer which is wound to produce a higher voltage output, which is then rectified and filtered (if you need high voltage DC) or used as-is (if you need high voltage AC). The AC voltage may also be applied to a voltage multiplier (consisting of a string of diodes and capacitors wired to sum all the capacitor voltages together into a higher DC output voltage).

With that said, let me give you two warnings:

(1) Voltages (AC or DC) in the range of 500 to 1000 volts are dangerous and can be lethal. GREAT CARE, EXPERIENCE and SAFETY are of the utmost importance. A person may not get a second chance to be zapped by 1000 volts....... Even if the shock doesn't kill you outright, the reaction to a shock (violent body movement) can cause injury due to contact with surroundings (i.e. smashing your arm against a wall as you involuntarily jerk away from the shock) or even broken bones due to full power, high speed muscle contraction far beyond what you can voluntarily produce.

(2) G/M tubes are very sensitive to damage by overvoltage or overcurrent. You need to know the voltage the tube runs at, what kind of quenching and dead time it requires and what voltage and current it expects to see when ionized.

You don't simply connect a G/M tube to "high voltage" and wait for the "clicks".......

Typically, the tube is run at a voltage close to, but below the voltage that it will start it's own arc (ionize). Then, an incoming high energy particle will ionize a few atoms of gas, the reaction will cascade and the tube will go into conduction. The rapid drop in tube voltage signifies detection of a particle.

What then? Unless the applied voltage is momentarily removed or decreased (dead time) to stop the arc, the tube will stay in conduction.

Most G/M tubes are self quenching, but this only works when the applied voltage is CORRECT, when the current during conduction is limited to the tube's specs and if the tube is operating within it's specified temperature range.

So, in summary, you need to know what you are doing in regards to SAFELY handling high voltages, and you need to provide the G/M tube with the correct voltage, current and (possibly) the correct quenching scheme (momentarily removing or lowering the tube's voltage below the ionization point).

Please be careful!

Grumpy_Mike: The best way to do this is to change the transformer to one with a higher turns ratio. The other way is to feed the transformer primary with twice the input voltage. Make sure the HT capacitors can take the extra voltage.

I can't believe you said that.

Krupski:

Grumpy_Mike: The best way to do this is to change the transformer to one with a higher turns ratio. The other way is to feed the transformer primary with twice the input voltage. Make sure the HT capacitors can take the extra voltage.

I can't believe you said that.

Why is that? A given transformer's absolute voltage limits are primarily determined by the insulation rating of wire used in the transformer windings. So doubling the input/output voltage of a transformer maybe quite practical if still within the insulation rating of the wire.

Usual method of doubling the output of a high voltage oscillator circuit is to employ a voltage doubler which comprises capacitors and diodes.
You mention a zener array, but without sight of the actual circuit you’re working with it’s impossible to advise further.

A voltage doubler has the advantage of not subjecting the secondary to higher voltages.

Can you give links for the geiger tube and for the geiger counter ? I would like to see the schematic for myself and read the specifications of the tube.

retrolefty:

Krupski:

Grumpy_Mike: The best way to do this is to change the transformer to one with a higher turns ratio. The other way is to feed the transformer primary with twice the input voltage. Make sure the HT capacitors can take the extra voltage.

I can't believe you said that.

Why is that? A given transformer's absolute voltage limits are primarily determined by the insulation rating of wire used in the transformer windings. So doubling the input/output voltage of a transformer maybe quite practical if still within the insulation rating of the wire.

Sorry but you are wrong. A transformer is designed and built to run close to magnetic saturation of the core (for highest efficiency). Any given core material will only support "X" number of volts per turn at a given frequency. Trying to go beyond that point (i.e. increasing the input to the primary) will only drive the core into saturation. The current will go way up, the heat will go up and the transformer will go up (in smoke).

The only way to use a higher voltage on a given transformer is to raise the FREQUENCY of the AC input (usually not practical with 50/60 Hz power lines).

Check with that guy named Faraday... he'll tell you all about it.

Check with that guy named Faraday... he'll tell you all about it.

I tried, they said he checked out sometime ago. ;)

The HV sections of many geiger counters are capable of voltages substantially higher than 500 V, but are regulated for a particular tube by a Zener diode string. It may be that all you need to do is add a couple of 200 V Zeners to that string. The HV filter capacitors are usually rated for 1kV or more, so it is likely that you can reach the needed 900V.

Here is a lousy schematic of one such geiger tube power supply: http://www.cooking-hacks.com/skin/frontend/default/cooking/images/catalog/documentation/geiger_counter_arduino_radiation_sensor_board/radiation_board_v5.pdf

It would be helpful if you could post the details of your board.

Edit: If you decide to make such a modification, DO NOT try to measure the high voltage with a standard multimeter. The 10 megohm input impedance of the meter will load down the HV circuit and give a seriously misleading reading. You can buy an HV probe or make one by adding a string of 9 x 10megohm resistors in series with the voltmeter input, which will divide down the voltage by a factor of 10 and not load the HV circuit so much.

As I recall most geiger tubes utilize an external series resistor between the HV output and the tube's anode. This is generally all that is required for the self quenching action, HV decreases automatically with increasing anode current. But of course the tube's datasheet is required to confirm proper HV and anode resistor values to use.

LEfty

hey guys... this is the problem i am having- i had this idea about hooking up a 7 inch d-22 (http://www.youtube.com/watch?v=TXnT14eg3f8) to the libelium Geiger board. I’ve already made the wand like an umbrella so to check food and anything else covertly (especially seafood) without attracting too much attention. (when detecting radiation in food it has to be a very sensitive tube) I’ve already built it, and got the software on the aruduino up and running; but i need to get the Geiger voltage right. The libelium says it works with tubes from the 400v to 1000v range but i am unable to find anyone, or any technical info on how to make the adjustment on the libelium board. for such a necessary adjustment i find it strange that there is nothing i can find on how to do this. basically i am hooking up a d-22 to a libelium...the only way it clicks is if i hook it up to the tube backwards/ oh yea it screams when i hook it up basackwards ...

I explained how to modify your board in reply #10 above (the schematic I posted is of the Libelium board). However, you may have already ruined the Geiger tube.

probably so...thank for your help/ i am just a chemist...when there was no documentation on planet earth on on just how to get the 500+ volts out of this board i think i just gave up - i've got too much on my plate now to learn this stuff right now/ i thought this board was set up for 500+ volts...it's just not. i guess my regular geiger will have to do... i had fun trying- -thanks /dave

I still have no idea what to think of it, because I don't know your hardware.

Making a circuit that produces 100V is easy, but a circuit for 1000V requires knowledge of high voltage design. Sometimes a circuit can hardly get to 300V, but sometimes 1000V can be reached with a simple design. It depends a lot of the quality of the coil or transformer. Also replacing the diodes with high frequency switching diodes with lower capacitance can have a lot of influence.

As written before, you can not use a multimeter to measure the high voltage. If you would read for example 600V, and remove the multimeter, the voltage could go up to 900V without you ever knowing it.

I'm still not sure if your Geiger tube requires such a high voltage. And if you are not an advanced electronics maker, you should not try to make 1000V yourself. Perhaps a circuit can be bought for those higher voltages ?

Krupski: Sorry but you are wrong. A transformer is designed and built to run close to magnetic saturation of the core (for highest efficiency). Any given core material will only support "X" number of volts per turn at a given frequency. Trying to go beyond that point (i.e. increasing the input to the primary) will only drive the core into saturation. The current will go way up, the heat will go up and the transformer will go up (in smoke).

Well apart from the basic physics you have almost everything else wrong.

A transformer is designed and built to run close to magnetic saturation of the core (for highest efficiency).

No it is not. It could be but if you are telling me that the core of a transformer is tailor made for every rating of transformer then you are very much mistaken.

Any given core material will only support "X" number of volts per turn at a given frequency.

No it is the core saturation we are talking about so current matters as that plus the number of turns determines the magnetic filed that causes the saturation that you are worried about.

Trying to go beyond that point (i.e. increasing the input to the primary) will only drive the core into saturation

That is simply nonsense, because as stated above real transformers you buy are not designed at these limits. Let's suspend sense and say they were designed on the limit. You argument assumes that transformer is being used to transfer the same sort of power as the transformer were designed to. Remember what we have here, it is a GM tube, it is a very high HT load, less than 1mA so even if it was designed on the limit of saturation the very light load on the secondary would ensure that very little current flows in the primary making it not even approach saturation.

The current will go way up, the heat will go up and the transformer will go up (in smoke).

Now this statement is also wrong, yes if the core saturates then the heat will increase but the likelihood of going up in smoke is vanishingly small, because to do this it would have to have been a very badly designed circuit having the ability to drive into the primary much more current that necessary. So again suspend sense and say it could, then when a transformer over heats what happens is that the wire melts and goes open circuit, it will never go up in smoke. A high turns ratio transformer blowing is not a spectacular sight.

I also speak from experience. I have worked with GM tubes and have made HT supplies with miniature mains transformers. A 240V to 6V transformer was driven backwards with 12V, That is I had a 12V signal fed into the 6V winding, this then produces 240 * 2 = 480V on the output. When rectified and smoothed this produced about 670V peak DC which I then fed into the GM tube through a 1M resistor for the quenching. This arrangement worked perfectly well with absolutely no heating of the transformer as you would expect if you take the theory of what is happening far enough.

Dave:

It is always a good idea to contact the seller with questions like yours. If they don't respond, there are lots of forums that are eager and willing to help. In particular I've found the "geiger counter enthusiasts" forum on Yahoo to be very helpful. There is still hope for your project -- the tube may not be destroyed, but it needs to be checked out carefully. There are procedures for determining the proper voltage levels to use, but they require a variable HV supply and some care.

I'm reasonably confident that my suggested modification to increase the voltage by adding additional Zener diodes will work, but you should certainly check with the board designer.

Jim

(when detecting radiation in food it has to be a very sensitive tube)

Well no. Have you ever put Brazil nuts under a Geiger counter? Lots of clicks.

What is important is the type of radiation and you do not get that from a Geiger counter as there is no energy measurement involved. Measuring the radiation from milk for example involves lots of lead shielding and very long counts. This is something you could not pick up with several people helping. So getting meaningful readings from sticking GM tube into food is not going to happen.

Real transformers are complex, but you need to remember that the currents in the secondary and primary are strongly coupled (thats the whole point) so that the sum of the amp-turns from the two windings is a lot less than the amp-turn of each separately, and saturation usually depends on that sum.

So when transformers are wound on the same bobbin the core never sees the separate amp-turns at all, whereas some high-voltage transformers with separate bobbins are different and the core sees the full amp-turns of each winding in different parts.

Anyway you used to be able to get pottery with uranium glaze on eBay (perhaps you still can, I think its a particular shade of orange) which very definitely radioactive since the glaze is partly uranium oxide.