Epe pic magnetometer

[amitech1982]

thanks, I use two 3.7V 3000MAH lithium batteries. and I did not have an oscilloscope, if I had one, I will have tested the sensor output. I'm afraid my sensors are the cause of defect, I recently bought them at an expensive price from Slovenia

[amitech1982]

I forgot to say that I use the microcontroller 16F877-20P, not the 16F877-20I or IP. Could this be the cause of the problem.

[SimonS]

Sensors are made by me, and they are 100% tested before send. And like it seen that you have problem with both, so I think problem is somewhere else. Try to use 9V battery or 3x Li-ion at first. It can be also problem too low voltage on voltage regulator. Because it is strange, that 5V reg give you 5.43V on output....
I don't know where are you from. But if you send to my address I will check and fix it.
No, PIC is not problem

[amitech1982]

thank you very much mr Simons, I changed another circuit CD4013BE and it's the same thing. I also used a 9V battery but same problem. I will change the 78L05 and I will give you the result immediately. About me I am from Tunisia.

[amitech1982]

I changed the 78L05 and same problem

[amitech1982]

I realized an astable multivibrator with the NE555 which generates a frequency signal about 71khz and then I connected the signal output instead of the sensor. and even as the sensor, the display shows 71705 then 71682 then 71420 and so on, ie an unstable reading! what did you think? can be a problem pic or programming?

[SimonS]

Hmmm seen strange here.
lm78l05 in 5% tolerance this mean 5.25 max output.
Why you have drift on PIC input is hard to say. But for sure is something wrong with power supply. Can you share your schematic? You can also send me to PM

best regrds
Simon

[amitech1982]

Excuse me, the multimeter battery is worn, that's why the voltage measurement is wrong, I changed this battery and I measured the voltage at the sensor terminal and I found 5.01V. I use a battery lipo 2S 3000mah, and she has 8.21V, I also tried a 3S lipo 13V and same problem.
For the schema, it's the same for John Becker's EPE Magnetometery logger project, but I redesigned the pcb with sprint layout.
I will upload the pcb right away.

[waltr]

I realized an astable multivibrator with the NE555 which generates a frequency signal about 71khz and then I connected the signal output instead of the sensor. and even as the sensor, the display shows 71705 then 71682 then 71420 and so on, ie an unstable reading! what did you think? can be a problem pic or programming?

Took a quick look at the schematic from page one of this thread.
Seems it is the PIC that generates the output frequency. Is this true?

I forgot to say that I use the microcontroller 16F877-20P, not the 16F877-20I or IP. Could this be the cause of the problem.

This will not cause the problem. The 'I' only means Industrial temperature range.

What are you using for the PIC's XTAL????
If a XTAL is it the correct one as specified in the PIC's Configuration values?
Also, if a XTAL the correct caps must be installed.

It is the XTAL connected to the PIC that determines the frequency and the frequency stability, NOTHING else.

Only other possibility is your frequency measurement is not working.

[amitech1982]

PCB EPE MAGNETO.pdf

EPE MAGNETO .pdf

[amitech1982]

Took a quick look at the schematic from page one of this thread.
Seems it is the PIC that generates the output frequency. Is this true?


This will not cause the problem. The 'I' only means Industrial temperature range.

What are you using for the PIC's XTAL????
If a XTAL is it the correct one as specified in the PIC's Configuration values?
Also, if a XTAL the correct caps must be installed.

It is the XTAL connected to the PIC that determines the frequency and the frequency stability, NOTHING else.

Only other possibility is your frequency measurement is not working.

Thank you for your reply. No, the PIC does not generate a frequency, it only reads the outputs of the sensors.
For the configuration of PIC I do not know ! I just program the PIC with the file MAGGY710.hex using JDM on serial port, and I use a quartz 20Mhz as mentioned in the schematic.
I will change the quartz and I will give the result.

[waltr]

Thank you for your reply. No, the PIC does not generate a frequency, it only reads the outputs of the sensors.
For the configuration of PIC I do not know ! I just program the PIC with the file MAGGY710.hex using JDM on serial port, and I use a quartz 20Mhz as mentioned in the schematic.
I will change the quartz and I will give the result.

Ok, The epe circuit oscillates and then the PIC measures the frequency.
Inverse of my above post but still dependent on the PIC's oscillator running correctly.

I did see on the parts list the XTAL type was not specified.
DO READ the PIC's Oscillator section (14.2) in the data sheet for ideas as to what XTAL should be used.
Without Source code you will be guessing as to what config bit setting is used for the PIC's oscillator setup.

[amitech1982]

Ok, The epe circuit oscillates and then the PIC measures the frequency.
Inverse of my above post but still dependent on the PIC's oscillator running correctly.

I did see on the parts list the XTAL type was not specified.
DO READ the PIC's Oscillator section (14.2) in the data sheet for ideas as to what XTAL should be used.
Without Source code you will be guessing as to what config bit setting is used for the PIC's oscillator setup.

I changed the quartz 20MHZ with another and two capacitors 33pF, and even problem. It remains to check the programming of PIC. Before that I will remove the circuit LM35DZ, may be that causes the problem of instability.
Here is the source article of the project (EPE magazine) and also the PIC Hex file and the source code.

[waltr]

According to the parts list and PIC data sheet the cap on the 20MHz XTAL should be 10pF not 33pF.

Is the serial data working correctly? All data passing without errors?
If so then the PIC's oscillator is probably running correctly.

Read some of the build article.
Another possible reason for unstable freq is movement of sensors and/or electrical or magnetic interference.
The section on Sensor Alignment & Wellyquipped states to ensure device is Away from magnetic and Metal interference sources.
Is the displayed freq stable if you take the epe away from house and other electrical?

[amitech1982]

According to the parts list and PIC data sheet the cap on the 20MHz XTAL should be 10pF not 33pF.

Is the serial data working correctly? All data passing without errors?
If so then the PIC's oscillator is probably running correctly.

Read some of the build article.
Another possible reason for unstable freq is movement of sensors and/or electrical or magnetic interference.
The section on Sensor Alignment & Wellyquipped states to ensure device is Away from magnetic and Metal interference sources.
Is the displayed freq stable if you take the epe away from house and other electrical?

According to the PIC16F87X datasheet page 122 table 12-2, the two capacitors must be between 15p and 33pf (see attached capture).
-Yes the transfer of data to the PC works without any problem with 10pF or 33pF (I tried both valeus of capacitors).
In the first experiments, the problem of instability persists even outside the house. Then I changed the 4013, the 78l05 and the quartz and I did not try the device outside the house.
Ivonic made a gradiometer using the same fg-3 + sensors, and its video shows great stability in its housing ... so if there is a problem, or the two fg-3 + sensors are not compatible with the PIC firmware (because the project uses two fgm3 sensors).