BPW34 photodiode radiation detector

[barry wilkins]

I have trying again to make a radiation detector using a semiconductor diode.
I tried last year but gave up on it.
Downloaded a number of ideas from the internet ,but again not much luck getting the thing to work.
One circuit used a fet but this amplifier this seemed to be biased wrong so it will not work.
I used a circuit using an opamp this would not work either with the BPW 34 ,it worked with a decapitated BFY 55 transistor covered with a little piece of Al foil over it.
The first circuit I used came from Elektor ,again this does not work properly ,when you shield the circuit to keep out the visible light it breaks in to oscillation.
Im sure this is caused by the capacity changing in darkness .

Has anybody tried these detector circuits?

Barry Wilkins

[stj]

Re: BPW34 photodiode radiation detector

it may help if you posted the chems.

but is it really usefull other than knowing your fucked - i mean it's such a small surface area on your sensor that it cant be acurate.

[ben7]

Re: BPW34 photodiode radiation detector

I have trying again to make a radiation detector using a semiconductor diode.
I tried last year but gave up on it.
Downloaded a number of ideas from the internet ,but again not much luck getting the thing to work.
One circuit used a fet but this amplifier this seemed to be biased wrong so it will not work.
I used a circuit using an opamp this would not work either with the BPW 34 ,it worked with a decapitated BFY 55 transistor covered with a little piece of Al foil over it.
The first circuit I used came from Elektor ,again this does not work properly ,when you shield the circuit to keep out the visible light it breaks in to oscillation.
Im sure this is caused by the capacity changing in darkness .

Has anybody tried these detector circuits?

Barry Wilkins

Not surprised, most circuits on the web are either only marginal, or have significant issues. Or, it worked fine for whoever designed it, but you have it built a little differently, and so it doesn't work right.

[barry wilkins]

Re: BPW34 photodiode radiation detector


Hi tried to attach a picture showing the circuit by B Kainka in Elektor.
If you look at the layout the circuit is different ,some of the resistors are of a different value and it seems that the cathode of the diode is ac coupled to the amplifier.
Thinking about it ,my BFY55 transistor is two diodes one forward biased and one reverse biased ( base to emitter) so perhaps that is making a difference.
Also circuits I have seen do have a coupling capacitor to the amplifier .

Barry Wilkins

[budm]

Re: BPW34 photodiode radiation detector

You are right that the circuit board does not have parts installed per diagram. I do not see the PIN Diode BPW34 on the board.

https://cdn.badcaps-static.com/pdfs/...8098d5cb9f.pdf
http://www.emant.com/324003.page
Using it for Geiger counter is another story.
See example circuit (SHARP) how it is used.

[barry wilkins]

Re: BPW34 photodiode radiation detector

Hi, you cant see the PIN diode it is on the other side of the stripboard.
Ac coupling the diode has stopped the circuit breaking into oscillation,all I need now is decent source of gamma radiation.
Barry

[goontron]

Re: BPW34 photodiode radiation detector

Hi, you cant see the PIN diode it is on the other side of the stripboard.
Ac coupling the diode has stopped the circuit breaking into oscillation,all I need now is decent source of gamma radiation.
Barry

crack into a smoke detector.

[eccerr0r]

Re: BPW34 photodiode radiation detector

Radioactive smoke detectors mostly use Americium which is an alpha emitter. Might be best to detect gamma rays by waiting for a thunderstorm or looking for a CRT and overdriving it...

On second thought CRTs generate X-rays... but it should be ionizing enough to work.

[goontron]

Re: BPW34 photodiode radiation detector

Radioactive smoke detectors mostly use Americium which is an alpha emitter. Might be best to detect gamma rays by waiting for a thunderstorm or looking for a CRT and overdriving it...

On second thought CRTs generate X-rays... but it should be ionizing enough to work.

he could just come up here to rocky flats :/

[stj]

Re: BPW34 photodiode radiation detector

open the window and point it towards Windscale / Sellafield nuclear dump!!!!!!!!!!!!!!!!!!
https://duckduckgo.com/?q=windscale&...t-wt&kv=1&kh=1

or order something from japan and then test the contents of the envelope!!!

[desert-rat]

Re: BPW34 photodiode radiation detector

On the gama rad. you could see if a doc. would fire up an x ray mch. I have found a few circuits for a e.m.f. meter , I am not sure if they really work , but all I would need to test one would be a ghost .

[stj]

Re: BPW34 photodiode radiation detector

you can buy emf meters for $10 on ebay.

it's only going to pickup every coil and transformer in the house though!

[barry wilkins]

Re: BPW34 photodiode radiation detector

Thanks for your comments ,to get a crt to develop X rays you need something like 25Kv ,the cone is shielded with steel and the face plate is lead glass. I dont have a colour tv with a tube any more.
I did see an idea were you ionised a length of wire to attract dirt and dust witch might have enough particles to detect.
I think I may of found out why my Fet circuit failed to work ,the diagram showed a JFET ,a similar circuit I saw used a 2N7000 which is a mosfet.
On holiday for a while so will carry on in a week or so.

Barry

[desert-rat]

Re: BPW34 photodiode radiation detector

I would think you could buy some alpha and beta rad. test samples . You can use a muler giger . tube , as all the old giger counters use . I have an old giger counter , it has some small vacuum tubes . It takes a bunch of batteries , like 1.5 for the fil. and 135 vdc , ect.

[barry wilkins]

Re: BPW34 photodiode radiation detector

Attached a couple of pictures
The correct circuit and the results of Am241 using a naked BFY 55 transistor
The BPW34 diode I bought just dont work ?

Barry