Geiger-Müller tube supply voltage generator

[PeterFW]

Hello!
This is bugging me for the past few days, i got other things to do but this keeps popping up in the back of my mind.

I would like a adjustable boost converter that can take 1.8v to 5v and step it up.
The output voltage should be from about 300 to 600V, up to 1kV would be nice but it has not to be.
Idle current... way under 5 mA would be nice, output current around 50 to 100µA.

Allthough analog stuff is not my expertise i have two rough ideas myself how to do this.
Involving transformers, analog switches and voltage multipliers.
Annyone done something like this?
I know there are a few design out there that do this, but they are closed source.

Greetings,
Peter

[ManateeMafia]

Sparkfun has this product with schematics https://www.sparkfun.com/products/11345

The schematic shows it as open hardware.

[SaabFAN]

You could also look at the Flyback-Converter. In my Philips Scope they use a flyback-converter to create the high voltage for the CRT.
Another method would be to turn DC into AC, transform that up with a small transformer and rectify it again. Diodes with well over 1kV are readily available.
If I remember correctly, the geiger tube has a very high impedance but becomes conductive if ionizing radiation enters the chamber with enough energy to trigger a chain reaction. The sudden increase in current causes the supply-voltage to drop to zero, stopping the flow of current and resetting the tube.
So from memory, I'd say a 555, a tiny transformer with a lot of windings and a high-voltage diode should suffice.
Don't know about the regulation of voltage applied to the tube, but I guess you could use a 1k Pot on the low side of a high voltage-resistor if you can provide sufficient isolation.
It is however important to ensure the high voltage cannot reach your low voltage circuit under any circumstances to avoid the thing going up in smoke like it happened to me last weekend. Sudden change in current caused a voltage-spike and suddenly I was sitting in a cloud of badly stinking smoke as a Bipolar DC-DC Converter turned 3Amps into heat^^

[WZOLL]

Don't forget the anode resisto

[JimRemington]

See this post on another forum: http://forum.pololu.com/viewtopic.php?f=6&t=1453&p=39331 In addition to the 555 circuit shown, as described, you can buy cold cathode fluorescent lamp supply modules for very little on the surplus market. They tend to run on any input voltage between about 2 and 12 V, with the output being in the range 200-1000 VAC (high frequency). All you need to do is rectify and filter the output.

[kwass]

There are some good circuits presented here: http://www.techlib.com/science/geiger.html#HV%20Generators

I've built the 2'nd one down (for 9 volts) and modified it to work more efficiently over a wide input voltage range.  It easily powers a smallish Geiger tube drawing around 100ua from 6 volt supply.  However, I can't come close to the size and efficiency of this supply I found on ebay:

http://www.ebay.com/itm/Geiger-counter-power-supply-module-dosimeter-NEW-1-HV-400V-high-voltage-/161038892259?pt=LH_DefaultDomain_0&hash=item257eaa7ce3

I've bought several of these and am extremely pleased with them and the seller's responsiveness.  (Shipping to the US does take some time, however.)

Currently, I see another seller selling the same HV supply for much less:

http://www.ebay.com/itm/SALE-400-Volts-power-supply-for-Geiger-tube-counter-radiometer-Unique-Lot-1-/221728803419?pt=LH_DefaultDomain_0&hash=item33a0110a5b

I'm nearly certain that the lower priced ones are being sold by the person that manufactures them.  He's also selling them in bulk at different voltages and used to (perhaps still does) customize them to your voltage needs.