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Topic: PMT tube with Arduino (Read 642 times) previous topic - next topic

volbog

Hello. I make the system of reading the decay of the photoluminescence of the sample with PMT R928 in photon counting mode.

At this moment I did the power of the PMT, buy amplifier.
 
But I stuck at the following problem:

Pulses after amplifier is 10-20ns, which is much smaller than the arduino 16 MHz, so I lose a lot of pulses and my measurements are going incorrectly.

How can I expand pulse to 50-100ns from 10-20ns?

wildbill

How can I expand pulse to 50-100ns from 10-20ns?
No idea, but even if you could, the Arduino will still be too slow - a single machine instruction takes 62nS. I rather think you will need much faster hardware. Take a look at the Teensy range, although even then you may need some very tight code to keep up with the PMT device.

volbog

I planned use CD54HC221F3A multivibrator to expand pulses.
Anybody us multivibrator to this purpose?

For me the max signal will be 10000 counts per second so Arduino or raspberry will be good solution.

jremington

Quote
How can I expand pulse to 50-100ns from 10-20ns?
Google "pulse stretcher circuit".

For more help, you will need to post the details of your existing circuit and equipment.

volbog

I did the electrical circuit for my scheme.



The LM257N-5V will be used for 5V power of the SN74LS221N monovibrator.

Will be this scheme work?

jremington

#5
Sep 16, 2020, 07:46 pm Last Edit: Sep 16, 2020, 08:12 pm by jremington
Probably not. Check the input requirements for the 74LS221.

There is a great deal of useful information at http://physicsopenlab.org/2016/01/26/diy-gamma-spectrometry/.

I use the PMT power supply and pulse stretcher circuit designed by Theremino (described above), and it works very well. You might still be able to buy the kit.

hammy

Use a hardware counter/divider chip so you only see multiples of pulses ?

ephitran

Toggle flip flops can  be used to double then quadruples . . . so on,  as of the clock dividers inside  the CPUs.

However it does not  work well with variable periods.  You can try  to solve the problem by software?

Good Luck!


Billhigdon

The Theremino does XRF analysis with a PIC & can use a PMT coupled to scintillating crystals
.
Check out https://www.theremino.com/en/technical/schematics
and https://www.gammaspectacular.com/blue/theremino-mca

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