PICKINI V4 - an easy to build, self adjusting PI detector

[Guzzi]

Thanks for the compliment, but the honor goes to Nick Holas, who helped me get started with his design.

Regards

Leendert

[Goaty]

It was +35'c here today and hotter elsewhere.

+40 tomorrow.

We had 42deg C yesterday - looks like it is on the way over to you. Been quite a few serious bushfires around the state so I hope you don't get any. I spoke to my son in northern NSW yesterday and he can't believe that the rainforest has be burning up there.
I thing we're back to a max of around 20deg C today!

Thanks Marty & Guzzi for posting the files. I haven't had a chance to look at them yet today but it's on the agenda.

[MartyJ1963]

@Goaty,,I know, it's probably been the worst bush fire episode I've known in my life time,,hope your son stays safe up there in N.S.W (My home state), it's heartbreaking to see all that beautiful countryside reduced to nothing,,hope they get it under control soon mate,,
I may build this little SMD board myself soon,,I've got some more PIC's on order,,,,keep us posted on your build,,Regards,,Marty

[Goaty]

@Goaty,,I know, it's probably been the worst bush fire episode I've known in my life time,,hope your son stays safe up there in N.S.W (My home state), it's heartbreaking to see all that beautiful countryside reduced to nothing,,hope they get it under control soon mate,,
I may build this little SMD board myself soon,,I've got some more PIC's on order,,,,keep us posted on your build,,Regards,,Marty

Thanks for your kind thoughts Marty. Seems like my son has had his fair share of excitement up there - he had a brown snake slither between his feet while push starting a workmate's car just last week - that got his pulse-rate up!

I'm just about to look at Guzzi's board layout and hope I don't get diverted again - Have 2 smd boards started already. I may get to finish one soon!

[Goaty]

Hello All
Just finished my Pickini SMD and it works.Not tested outside, but promising.
Used Pickini HEX 4.4. I used the bottom layer as ground.[ATTACH]48338[/ATTACH][ATTACH]48337[/ATTACH][ATTACH]48339[/ATTACH]

What size resistors and caps did you use? I'm just about to order some and can't decide between 1206 or 0805.

[Guzzi]

Hi all

1206 is my favorite and the caps are Tantalum and two Elco's. There is no bigger value than 220 uF in that size.
If you use 805 do not sneeze.

[6666]

What size resistors and caps did you use? I'm just about to order some and can't decide between 1206 or 0805.

You can find 1206 in the carpet.

[Goaty]

Hi all

1206 is my favorite and the caps are Tantalum and two Elco's. There is no bigger value than 220 uF in that size.
If you use 805 do not sneeze.

Thanks Guzzi
I sort of worked out from your board photos that you may have used 1206s but if you think 0805 will fit I will probably go with them. I have successfully used as small as 0603 but I think it would be a bit of a stretch to get them between the pads on this board. Have to be particularly careful with the smaller sizes when there is a track to be bridged between the pads and I often put a narrow strip of Kapton tape under the component just to be sure of no short circuits.I have read somewhere that the larger sizes are more prone to stress damage when soldered in place. It all seems to be a juggling act with smd R & C as there is no 'give' in their bodies and the solder pads can be pulled free - it gets worse with increasing size. Working against this is the lower wattage of the smaller components.

Worse than losing components through sneezing is having them fly out of the tweezers - I usually just get a new one as it's not worth the effort and time spent looking for them.

@666
I think I could lose a whole PC board in my carpet - the military would probably be able to use it as camouflage! It's amazing how many small items just disappear when dropped on it and the multitude of component pigtails embedded it it make it a painful exercise to search by running your hand over it.

[MartyJ1963]

Any progress yet anyone? It's gone very quiet on here lately!,,LOL,,,Regards, Marty

[6666]

Hello F117
I have been experimenting with some analogue comparator circuits and how I can use them to detect a signal in a PI detector,
so I am just wondering how you configure the comparator inputs in your PIC.

Do you use the comparator inputs as inverting mode or non inverting mode, or do you do something different as I am not sure how a PIC comparator works compared to an analogue circuit
thanks.

[F117]

The PIC 16F1824 has 2 analog comparators onboard. They work exactly as any other comparator but have an input range of 0 - 5V.
And of course a lot of settings in SW: hysteresis, output inversion, output internal/external, clock sync, ...
1 of them is used to measure the pulse width of the flyback pulse.
The attenuated ( /2 - to match the 0 - 5V input range of the comparator) pulse is connected to the negative input of the comparator = pin 9
The positive input = pin 10 is connected to a DC slicing level coming from the PWM output pin 2 + RC filter.
The DC level of the flyback pulse is measured with an ADC in steady state, and the slicing level is set 0.5V lower.
This results in a positive output pulse = flyback pulse width at slicing level.
This pulse width is measured by gating a timer running at 32 MHz with it ( resolution = 32 ns).

You can hack the schematic by connecting an external voltage to the positive input pin = pin 10 with a potmeter, eg.
To do this, you need to disconnect R19 = series resistor between PWM output and comparator input.

This manual adjustment of the slicing level can be an advantage in very noisy environments.
This is also what v4.2 of the software does: adjusting the sensitivity setting will increase/decrease the comparator slicing level - this is done internally by modifying the PWM output.
http://users.telenet.be/willaert/MD/.../software.html

[6666]

Thanks F117, much appreciated, you are very clever .

[MartyJ1963]

@Goaty,,,Any progress on the Pickini4 SMD yet? Regards,,,Marty

[Goaty]

@Goaty,,,Any progress on the Pickini4 SMD yet? Regards,,,Marty

Hi Marty
I’m afraid “ I have some good news and some bad news” as the saying goes.


The good news is that it works and the bad news is that I have a problem with mine.


The story is that my impatience got the better of me when it came to waiting for parts to arrive from overseas so I cobbled up some shortcuts to get it going. These involved stacking smd resistors to get the required values in a couple of places and tacking in place a th BC548 instead of the sm version.


When I applied power I was relieved to get the startup tones and the auto-tune ticking as this meant that the programming of the soic pic using my home-brew socket had been successful. But there the joy ended as I was greeted by the fault tone.


I eventually found that I could get past this by tweeking the sensitivity pot and it came to life and responded to metal waved near the coil but if I powered it down then up again it would not work until I again played with the sensitivity pot.


So, at this stage I plan to go over the board with the multi-meter and CRO and collect some info and also wait for the parts to come.


In the meantime I have been reading through all of the posts in this topic to glean as much info as possible on how the whole thing works. I have an idea that it may be to do with the comparator slicing level mentioned by Bernard in posts #739 and #552 so I will work on this for a start.


I will post more info when I get it

[F117]

If you programmed the 4.2 hex file, the comparator slicing level is influenced by the sensitivity setting. It is normal that you can adjust it out of the range of the analog flyback pulse, resulting in the error tone. Make sure the potmeter voltage goes from 0 to 5v and not the other way round. Turn it up until the normal tone turns into the error tone and then down again until you get detection tones again. This would be the best sensitivity setting.
So, everything appears to be normal.