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Problems with mark Stuart's PI detector

A

Anonymous

Guest
Hi again !
I'm still having the problem which is: At power up the pulses are too long (2ms on, 10ms off,etc...). If I press RA4 at power up the pulses will be about 50us but why does it always start with 2ms pulses? Another problem: I cannot save the settings to EEPROM by pressing RA4 when power is on. When I power up again the pulses are 2ms again. Why?
 
Hi Sami
I wrote the code published on Carl's side and as I wrote in the documentation it was only a test code for pourly testing. I will not recommend this as a ready to go code but more as a base for start for building this detector.
As I also wrote, I do not wand to answer a lot of questions on this design as it was something that I just made with left hand a late night and only reason for publising it was to help all those there wand to get started.
Well, here is something to check out:
Are you using 16C84 (I no its dead) or the newer 16F84?. If 16F84 checkout what the difference is there is a web page for it... again I do not have time for it!.
What I used for programming was a Startkit PICSTART16B from Microchip, and on this equipment you can choose to enable or disable the build in watchdog, it most be disabled, there is some way to add this to the code... try to figure it out, or use original programmer. If you do not the processor will reset itself constantly... no good.
I got some mail from people that succeded, if I can find them I will send you a personel mail.
Sorry that I can not do better at the moment, just too many projects ahead of that old one.
Hope this helped a little.
Mark
 
Hi Mark,
thank you for answering. I've tried both 16C84 and 16F84 and the result is the same. The pulses are too long at startup and saving is not possible. If there is anyone who has got it work correctly, please tell me if you have done any changes to the code. The only way now to get it work is to start the thing without the search coil and pressing RA4 so the pulses will change to 50us and then I can connect the coil (With 2ms pulses the current draw is too much for the circuit)
Cheers !
-Sami R
 
Hi Sami
I remember one guy that made this circuit with a very low impedance coil that had a problem that sound like yours. I think what he did was change the R22 of 10K to a 1K and mount another 10K from the IC5 output pin to the 5 volt. What will happend then is that when the PIC starts the output are three stated and the 10K will send bias current to the npn transistor which will keep the gate of the mosfet low until the PIC startup is done and it will take over.
What if you do not connect the coil at all, can you then change the puls settings and save it ?
Mark
 
Hi Mark,
thanks for answering, if I power up without the coil and change the pulse width to i.e 50us and then connect the coil it works, but I still cannot save anything. Every time I power up, the pulses are 2ms again. I'll try the modifications you described and we'll see what happens.
Thanks again !
-Sami R
 
Hi again,
now I can start the circuit with the coil connected but I have to press RA4 and RA1 during power-up to make the pulses about 50us, otherwise the pulses will be 2ms and the circuit draws a huge current. The saving still doesn't work. What could be the reason?
 
I made this myself and had to re-write the code completely.Sorry,that was a long time ago and I dont have it now.
 
I have just built up the unit from scratch using the pcb & Hex code burnt into a PIC16F84. Did anyone have to mod the cct. other than the suggestions already made i.e. is the pcb correct and/or the circuit that is on the net? Are there any differences between the available cct & the one supplied with the purchased kit? Sami did you have any joy with your problems?
Any help greatly appreciated.
 
Hello
I start this project 1 mounth ago i build a pic programmer to program the pic16f84 with the code.
I use the ascii file (from pauls)and i assemble it myself (on pic16f84a-04). after a small stugle with the program i decide to modifie the program to make it work proprely. (as writen by the first programmer)
several detail was not correct in the program but the core is very good.
after having the chip working i decide to improve the program to add a 4 save bank with a save button and a recal button.(7 button total) I had also the possibility to adjust the W.B.N (so every thing is ajustable.
I did not tried the chip in the circuit becose i still having problem with the circuit.
I don't understant the use of the diode D4 it cut almost all the signal from the slope of the hight peek of the coil.
for the ascii file of both corrects programmes please send me a e-mail (mthibault@polymtl.ca) i will sent you the file as attachement. i hope somebody will place it in a web site, i will not.
Hope this help someone
 
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