555 Geiger Counter

221

04:44:50

Basic concept is talking 9vd and pulsing that with a 555 timer then pushing to a transformer using a mosfet before reaching the geiger tube. Bulb substituted for tube. 

Added step down to 5v for sensor use.

Will gladly accept feedback

This circuit is adapted from https://www.instructables.com/id/Simplest-Geiger-Counter/

published 7 years ago

2ctiby

7 years ago

I think that your zeners and bulb are connected wrongly to the regulator?

MrRedBeard

7 years ago

You're right the bulb was backwards but the zeners are right. Still getting used to this.

MrRedBeard

7 years ago

Wish there was a way to place notes on the schematic.

2ctiby

7 years ago

I was thinking more about your wire from the zeners connecting to the wrong position on the regulator...shouldn't that wire join between a capacitor and a diode rather than as shown here?

MrRedBeard

7 years ago

Hmm I'll check it. Thanks!

MrRedBeard

7 years ago

Wiring corrected and a change of the lamp settings corrected the voltage making it more consistent.

MrRedBeard

7 years ago

Added step down to 5v for sensor use.

2ctiby

7 years ago

Looking good. Now in the mosfet settings..... turn the KP fully clockwise to 100mA/V²....that will make your transconductance more realistic and show better here too. (and notice also then how the 400V is reached more instantly). Don't worry about altering other values here such as the threshold, since it is insignificant in this setup. Could the transformer be altered to reduce the high current through the mosfet?..maybe something like this... http://everycircuit.com/circuit/5853560564875264

MrRedBeard

7 years ago

Thanks 2ctiby. Looking into it. Some of this is going to depend on what I have on hand for the build but will definitely consider it for when I order parts for future builds.

MrRedBeard

7 years ago

2ctiby to lower the Amps drawn - rather than changing the transformer I added a 50 ohm resistor which essentially does the same thing.... I think.

2ctiby

7 years ago

Right on....I was going to suggest a resistor, but then I considered the power that it might use... (V=IR)...then at 9V with 50 Ohms....find the current I.......then multiply I x V to give the power in Watts. How does the Watts power answer stand considering availability, price and bulk size of such a resistor in your circuit?

2ctiby

7 years ago

Or...P=V²/R ..... either way ...power is 1.62 Watts here, so that may work if you are happy with obtaining that resistor....The decision gets a bit harder if say the resistor was 10 ohm here, with heat etc...all good fun.

MrRedBeard

7 years ago

Ah good points. Might be ok for first prototype because I have the parts but after that I need to get the different transformer.

MrRedBeard

7 years ago

Wish the tolerance for resistors or well everything were configurable.

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