PICKINI - an easy to build PI detector

[F117]

The input voltage to the PIC should be between 0 and 5 v and is clamped internally by 2 diodes.

[gavabeach]

Hello Bernard,yesterday i make a test in the beach and i want to coment what when the sens pot is in the center always sound and seems
inestable,only stay ok at the begining of the potentiometer.
I question if it is something wrong ( adjust of 8 v. or something else ...) because the Vbat = 18 v.
Best regards.

Jesus.

[F117]

Make sure that the multiturn potmeter is adjusted at 8V.
The instability is also influences by external noise sources.
Inside the house eg I can only turn up the sensitivity very little . Also make sure that the coil is properly shielded and shield connected to gnd.

[gavabeach]

Ok , thanks Bernard.

[6666]

Thanks F117
I have ordered a16F1824

[Dixix]

Pickini with crystal

Hello Bernard and all other
I am so in love with the project that I built the other version with crystal (with 16F616 and 20MHz Xtal). I am puzzled: The Pickini with crystal works excellently with the basket coil and the flat coil. For the small basket coil amazing distances ( 1 Euro about 25cm). I have tried without shielding in the house. My version without crystal (with 16F1824 and internal 32MHz oscillator) does not work with flat coil and with coil basket bad. Good but with some normal coils. A curious difference.
Dirk

[F117]

Hi Dirk,

nice coils you've made !

I am not a coil specialist and haven't tried with a "basket" coil yet. In theory - as far as software is concerned - there should be no difference between the 2 microcontrollers, except that the 16F1824 with internal 32 MHz oscillater has 1.6 times more resolution than the 16F616 with 20 MHz crystal oscillator.

I guess the only way to verify the differences is to measure the output signal of the front end amplifier that goes into the microcontroller with an oscilloscope...
If you haven't got an oscilloscope you can also try 'blindly' to slightly modify the 8V offset for the opamp with the multiturn potmeter.

Best regards,
- Bernard

[F117]

My version without crystal (with 16F1824 and internal 32MHz oscillator) does not work with flat coil and with coil basket bad. Good but with some normal coils

Dirk,

When you say: "does not work", does it mean that you get a continuous detection tone (due to instability) or no tone at all when metal is near the coil ?

[Dixix]

Yes, I mean that I have a continous detection tone. Switch on - audio welcome - 2x tics (Pot is in minimum position) and than continous tone.
Dirk

[Dixix]

Hello Bernard,
When I measure output signal with Oscope on the LM318 can I use TP2? Or directly on pin 6 from the Opamp?
Dirk

[F117]

Dirk,

please measure TP2 or pin 8/9 of the microcontroller. This is the attenuated version of the opamp output.
See if you can spot any differences when different coils are attached.

The only difference I noticed in the software is that with the 16F1824, the incoming signal slicing level for the comparator is a few hundred millivolts higher than with the 16F616....

[6666]

After a very slow boat from china my 16F1824 has arrived, so i programmed it with a pickit 3.

At first I was getting a error message #0045 which seems to mean that the pickit could not find the pic
so i altered the pickit to supply the 5volts to the pic and it worked.
To do this in MPLAB IDE 8.76
click on programmer
then settings
then POWER
then click "Power target from pickit3"
click apply and ok
then it should program ok.

Now just have to test the PIC.

[6666]

F117
does the 16f1824 stop sending out a TX pulse when it detects low volts ?

[F117]

F117
does the 16f1824 stop sending out a TX pulse when it detects low volts ?

No, operation continues as usual. It just sounds the low battery alarm tone every 25 seconds.

[6666]

No, operation continues as usual. It just sounds the low battery alarm tone every 25 seconds.

Thanks F117