Polish Pi

[Andi68]

C12 ?

[dbanner]

The pulse rate can be increased to 500Hz by changing C2 to 33nF. This change allows the integration capacitor C12 to be reduced from 0.47uF to 47nF. The circuit is now 10 times as fast as it was and will detect a coin being thrown through the coil.

Sandbanks schematic from original article.

[MartyJ1963]

DB,,,Can you post the pcb you used with the mods pointed out if possible please? I've made quite a few Polones but have never had any single one of them work yet. Andy (Silverdog) even sent me a proper polones pcb about 2 years ago and I couldn't even get that one working. On all the unts I made the Mosfet was get getting extremely hot, too hot to even touch for a second, and tht was with the coil attached and without. No matter what I did, changed etc, none would work. None had excess flux on the pcb, no solder bridges etc, I never could work it out. Thanks, Marty.

[dbanner]

I used this version. A bit dated, but it works.

Many people have built variations of what is essentially the "Sandbanks" using many different layouts, and I suppose they all should work.
One thing I noted in the original article is that the 4011 must be an unbuffered "A" type. The buffered "B" type will not work in this circuit. At least that's what the article says.

[MartyJ1963]

Thanks DB,,,,Did you use an ordinary 4011 or the unbuffered 'A' type?,,Thanks, Marty

[MartyJ1963]

DB,,,I've translated the file you posted earlier in case anyone needs it, regards, Marty

[Hammerhead]

Dear Hammerhead
The resistance of 1M that is just above the zener if I am not mistaken is 220R
The 18k resistors above the 1000uf capacitors do not correspond either
There is indeed an error in the diodes
Can you post the board you are using?
regards

https://youtu.be/8oYblCz8Yhk

[Hammerhead]

Hammerhead, please check out the four diodes in the charge pump circuit. Make sure they are correct orientation.

I point to the diode which I think needs to be reversed.

I do not know where the wrong This is another version Please help
https://youtu.be/8oYblCz8Yhk

[dbanner]

Thanks DB,,,,Did you use an ordinary 4011 or the unbuffered 'A' type?,,Thanks, Marty

To be honest, I just stuck a chip in the socket, a 4011. I just opened up the box to have a look and it's a Toshiba TC4011BP. According to the data sheet, all the outputs of the gates are provided with the inverters as bufferes, so I guess this is a buffered CMOS chip. It works, so I'm not sure why the original sandbanks article spoke to using only the unbuffered version.
I think the unbuffered would have a suffix "UB"

If you have a look at the logic diagram of a buffered NAND gate, you will see inverters at the outputs of the NAND gates (I refer to a CMOS quad nand gate chip).

Maybe someone else can say what chip they used for the 4011. I put the datasheet of the one I used so you can see clearly that it is a buffered type.

I will look to see if I have a "UB" type just to try to see if it makes any difference.

[Andi68]

@dbanner

I have a different circuit diagram, but the mods from the Sandbanks
also work with the Polish PI, I tried it myself

[dbanner]

Andi68, can you tell us which 4011 chip you used, I mean does it end in a suffix "B" or "UB"

[Andi68]

I am using a CD4011BE

[Andi68]

Texas Instruments

[dbanner]

Well that settles the matter, contrary to the sandbanks article, the buffered version works. I think CMOS technology in the late 1970s was not as good as it is today. The input/output characteristics of the gates in those days were probably not as good.
I post this document I found online from Texas instruments for those of you who are interested in this subject.

[MartyJ1963]

As I've said, I've built a few (too many) of these Polones and none of them worked,,,The closest I got to the exact same workings/sound/detection ranges and layout was when I built the PI Italiano,,and that worked straight away from first switch on,,,even the pots on the Italiano were wired exactly the same as the Polones. Regards, Marty