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frequency counter not displaying anything

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frequency counter not displaying anything

Postby shailesh=p » Sun Nov 29, 2009 11:51 am

hi i am shailesh i have build the mag fre counter with all the modification such as connect all pull up resistor to +ve rail , wired the cir. on veroboard, double check the connection error , ground the un used pin 7,8,9,10 of display 16*1 lcd namedJHD161a only available,use 16f628a with the hex file of mr. niras vu3cns. I have succesfully progrramed the chip ,and verified by the win pic 800 v3-64 . but still didnot get any thing on display. so, i changed the display but no result.Now please give some guidence on the issue, and help me out. I want mention that i have not connected any rf source to the input before , when i connected one no result once again. also use normal opration by directly ground the conection insted of using switch. and not connecting any of the two switch ,because i just want to see the result. What should be expected on frist switch on , on the display? When i measered the voltages on various pin on pin 2,3, voltmeter pin flutuate a little ,no rf source connected. Please help. thank for the help in advance. shailesh.
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Postby cutedrummerboy » Sun Nov 29, 2009 10:58 pm

have you grounded the body of the crystal?? if, then do not do that. actually the crystal available in india especialy the KDS made, often get short with there body. then if you grounded the crystal, it can not resonate. so please check this first. you can chenge the crystal also.
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about the not displaying lcd of mag counter

Postby shailesh=p » Mon Nov 30, 2009 11:01 am

no i havent grounded it. well should i connect mclr pin to +ve through 10k resistor? During googeling i found some counter had connect this pin to vdd through 10k resitor. Is it possible that i can conform the working of lcd or that of circuit is working or not. Please help me as this is my frist micro project. and thank for replay
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Postby vu3cns » Mon Nov 30, 2009 3:47 pm

Hi,
You need to connect MCLR to positive directly or through a resistor, unless it won't work.
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Re: about the not displaying lcd of mag counter

Postby mvs sarma » Tue Dec 01, 2009 1:56 am

shailesh=p wrote:no i havent grounded it. well should i connect mclr pin to +ve through 10k resistor? During googeling i found some counter had connect this pin to vdd through 10k resitor. Is it possible that i can conform the working of lcd or that of circuit is working or not. Please help me as this is my frist micro project. and thank for replay

It is possible that you need to maintain approx0.7V on pin3 of the display(contrast pin) for proper display. For this purpose you need to tweak R5 properly while supply is 5V DC.
the MCLR pin is show connected directly to Vdd, and all of us this connection is working. I have at least 2 such meters with 16F628A working.
Regards
Sarma
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Postby shailesh=p » Tue Dec 01, 2009 11:06 am

Thank you for my question to both of you , sharmaji and niras. Now when I disconnect my 10R resistor from pin 3 of lcd it worked. it showed 4.914999mhz<1R what does it mean? Ihave not connecting any thing to the input .How can I make it possible to read it 0.0000000mhz when I apply power to the circuit, as i want to display direct fre. Also tell me ,that if I do not connect the 10R to pin 3 will it make any diffrenc to it , as now the counter shows atleast something on it. Please excuse my all this questions as I am very happy that it finally worked. I go through the article but I can not understand it properly. Please explain how can I read direct fre. Once again thanking you for showing interest to my questions. waiting for your replay.
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Postby mvs sarma » Tue Dec 01, 2009 1:09 pm

shailesh=p wrote:Thank you for my question to both of you , sharmaji and niras. Now when I disconnect my 10R resistor from pin 3 of lcd it worked. it showed 4.914999mhz<1R what does it mean? Ihave not connecting any thing to the input .How can I make it possible to read it 0.0000000mhz when I apply power to the circuit, as i want to display direct fre. Also tell me ,that if I do not connect the 10R to pin 3 will it make any diffrenc to it , as now the counter shows atleast something on it. Please excuse my all this questions as I am very happy that it finally worked. I go through the article but I can not understand it properly. Please explain how can I read direct fre. Once again thanking you for showing interest to my questions. waiting for your replay.

R5 connected from Vcc to PIN3 of the display is 10K but not 10R as you mentioned.
manage to operate the "IF seclect" switch few times, till you get "MHz<D",
now it would show the frequency directly without any OFF set.
if you intend using it on a rig, you may know the IF offset. VU3CNS has provided for many offsets. you can select one.

Then you may have to select whther your LO is above the if, below if and if any negative value is expected, there is provision of reversal ( VFO-IF & IF-VFO)
For more details, you may read the "reda me from the zip file you got. It is almost self explanatory.
Regards
Sarma
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Postby shailesh=p » Wed Dec 02, 2009 10:35 am

Sharmaji, thank you to pointed out the mistake. It was such a small mistake , but if you carefully look at the circuit diagram the resistor just look like 10R . But now when you pointed it out the 'k' is not easily figure out. Any way , now I have connected it to pin 3 and find the direct reading on meter. Now it displays 0.0000001mhz . I have build a test vfo circuit [ using 8mhz crystal insted inductor] which is from this site, but with only one buffer and out put is taken from buffer amplifier's emmiter resister through .1mfd and connect to the in put ,but display doesnot change.Then I tune around 8mhz on sw radio I find the signal on it so the test circuit isnot the culprit. Well can you give some advice on it? Well I should mention that I have used bc547 insted of 2N2222 does this make it any diffrence due to sensitivity changed? The article sugest the sensitivity is around 150-200millivolt whereas output of the test circuit is around 1v p-p . Can you suggest me a good way to test the counter and calibrate it also, as I want to build a ladder crystal filer for my ssb receiver, it requier direct reading with veru good acurecy . Thanking you for showing interest ,and sugetion on my post. shailesh.
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Postby mvs sarma » Wed Dec 02, 2009 11:32 am

shailesh=p wrote:Sharmaji, thank you to pointed out the mistake. It was such a small mistake , but if you carefully look at the circuit diagram the resistor just look like 10R . But now when you pointed it out the 'k' is not easily figure out. Any way , now I have connected it to pin 3 and find the direct reading on meter. Now it displays 0.0000001mhz . I have build a test vfo circuit [ using 8mhz crystal insted inductor] which is from this site, but with only one buffer and out put is taken from buffer amplifier's emmiter resister through .1mfd and connect to the in put ,but display doesnot change.Then I tune around 8mhz on sw radio I find the signal on it so the test circuit isnot the culprit. Well can you give some advice on it? Well I should mention that I have used bc547 insted of 2N2222 does this make it any diffrence due to sensitivity changed? The article sugest the sensitivity is around 150-200millivolt whereas output of the test circuit is around 1v p-p . Can you suggest me a good way to test the counter and calibrate it also, as I want to build a ladder crystal filer for my ssb receiver, it requier direct reading with veru good acurecy . Thanking you for showing interest ,and sugetion on my post. shailesh.

If Doctors commit the same small mistake , only one patient would die,
Our educational system is to be blamed that gives marks for the steps, even if the answer goes wrong.
I feel we, the engineers have to be cautious not to make mistakes.

If you see the schematic carefully--- yes, i saw it it can't be 10R it is clear as 10K, though the component value could have been shifted outside the symbol for clarity.
regarding test, the coupling cap shown as input to final stage is much less. So try to use low value like 100pF.
Mainly you need a screened wire with ground connected to the emitter resistor bottom and the signal taken from emitter point with a 100pF cap. the screened wire should also be connected properly at the counter.

If the front end amp is working, even if you touch the 100 ohm resistor input point, it would display the power induction frequency at near 50Hz.

To ensure that the front end amplification at the counter is working, there is a way. remove the F628, switch on and with no signal input, measure the DC voltage at collector of the Q1 of the Frequency Counter and it should be near half voltage i.e., 2.5V. If not you need check the components used there.
For very good accuracy, you have to trim the trimmer cap C6 while applying a known accurate frequency. generally what we do, is make a 20 turns of 23swg copper wire at 6"dia, connect this coil to frequency counter. with a channel like Doordarshan tuned, take this coil close to your TV is at the back side, near the LOT , the counter would read 15.625KHz
this is a standard frequency and is dependable. While measuring, you may trim C6 to get the correct value.
I don't expect the oscillator you made need to give 8MHz so accurately.
it all depends on many parameters, the crystal itself, like temperature, crystal loading etc. you may read the theory of accuracy and stability.

All the best.
Regards
Sarma
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Postby shailesh=p » Thu Dec 03, 2009 10:42 am

Well, Sharmaji I totally agree with your point of view, but I want to tell you that of many circuit I have built in the past ,I never make such mistake and all my project worked for me. Any way thanks for your valuable advise I will take more attention on the part list in making any project in future. Now I have removed the chip from the circuit and measur the voltage at the collector , it shows 5v solid that means the front end is not working properly as you mentioned.so I am going to change the transitor the origenal 2n2222 . I will let you post the result afterward. For about 8 mhz ocilator it is just for testing and not for calibrating the counter. I just want to see the result on my counter before i put it in to right enclosure. By the way can you predict the fault of front end transistor showing 5v insted of 2.5v ? Well I also want to draw your atention that I an not an engineer just an electronics enthusiast. So may be my knowledge is limited in this filde that is the reasone that I am asking such a premitive question but you are a great help for the people like me and I am very thankful for it. Thanks from Shailesh.
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Postby mvs sarma » Thu Dec 03, 2009 10:01 pm

shailesh=p wrote:Well, Sharmaji I totally agree with your point of view, but I want to tell you that of many circuit I have built in the past ,I never make such mistake and all my project worked for me. Any way thanks for your valuable advise I will take more attention on the part list in making any project in future. Now I have removed the chip from the circuit and measur the voltage at the collector , it shows 5v solid that means the front end is not working properly as you mentioned.so I am going to change the transitor the origenal 2n2222 . I will let you post the result afterward. For about 8 mhz ocilator it is just for testing and not for calibrating the counter. I just want to see the result on my counter before i put it in to right enclosure. By the way can you predict the fault of front end transistor showing 5v insted of 2.5v ? Well I also want to draw your atention that I an not an engineer just an electronics enthusiast. So may be my knowledge is limited in this filde that is the reasone that I am asking such a premitive question but you are a great help for the people like me and I am very thankful for it. Thanks from Shailesh.

keeping BC547, check whether you have connected the C B and E correctly?
BC547 follows left to right CBE order of pins as you see the transistor facing you and leads kept downwards
Check that the transistor is placed properly in the breadboard. w.r.t., the biasing arrangement
if you read 5V on the collector itself, means that the bias is missing and transistor not conducting or is faulty
BTW, measure the voltage across base and emitter, it should be 0.7V DC approximately. if this is not there, you may check the resistor 47K removing it from the circuit. by DMM in Ohms range and replace it if needed. now restore the PIC.
By just touching the active point ( input pin ) you should read in direct measurement mode, with 1 sec time base, a value of 50Hz approx, indicating power induction
I had already told you about calibration.
enthusiasm is enough. but with a scientific and methodical approach. all the best.
Regards
Sarma
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Postby mvs sarma » Thu Dec 03, 2009 11:20 pm


Shailesh,
I have tried the Bc547. it is showing 2.5 V DC on collector with a 100K in place of the 47K resistor mentioned.
So, you may replace it with a 100K resistor. Check the balance and post results. All the best.
Regards
Sarma
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Postby shailesh=p » Fri Dec 04, 2009 11:22 am

Hello sharmaji, sir I have made the nessesery modification to my circuit ,like change the 47k to 156k [ only because I find it on my bench] ,read the voltage it showed around 2.5 [ on analog meter] ,and BE junction .5 or somthing . Then I put the chip back , touch the input and it shows 50hz or a multiple of it ,not steady but workrd, sometimes it displays some other frequency around 3 to 4 khz . Then i connect my 8mhz test circuit ,after a second or so it displays 7.999234mhz. o.k. now It is working. I want to tell you that when I measuring voltage ,with chip on , the input of the pin i.e. 2,3,fluctuate at 1hz rate and display the same result on lcd.[ I mesured the voltage at pin 2,3, with multimeter] Well that is not a problem , but as I am curious by nature, if you have any explanation , plese share it with me.Any way I want to thank you and all contributer to show interest and guide me to complete the project.I also want to thank the hamradio india team for providing me the file ,as you also did the same, I wish that many more interestin project i will see in future. Sharmaji thank you very much, I will waiting for your comments . thankinkig once again all of you ,shailesh. 73's.
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Postby mvs sarma » Fri Dec 04, 2009 12:10 pm

shailesh=p wrote:Hello sharmaji, sir I have made the nessesery modification to my circuit ,like change the 47k to 156k [ only because I find it on my bench] ,read the voltage it showed around 2.5 [ on analog meter] ,and BE junction .5 or somthing . Then I put the chip back , touch the input and it shows 50hz or a multiple of it ,not steady but workrd, sometimes it displays some other frequency around 3 to 4 khz . Then i connect my 8mhz test circuit ,after a second or so it displays 7.999234mhz. o.k. now It is working. I want to tell you that when I measuring voltage ,with chip on , the input of the pin i.e. 2,3,fluctuate at 1hz rate and display the same result on lcd.[ I mesured the voltage at pin 2,3, with multimeter] Well that is not a problem , but as I am curious by nature, if you have any explanation , plese share it with me.Any way I want to thank you and all contributer to show interest and guide me to complete the project.I also want to thank the hamradio india team for providing me the file ,as you also did the same, I wish that many more interestin project i will see in future. Sharmaji thank you very much, I will waiting for your comments . thankinkig once again all of you ,shailesh. 73's.

Nice to see it working, all the best
the active input is active and any extra connection on pin2 and 3 of the PIC would work like a probe and would interfere working, that is why you get fluctuation
if last digit is not important you can use 0.1sec time base by selection but 50Hz would then be 4, 5 or 6.
Regards
Sarma
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Postby shailesh=p » Sun Dec 06, 2009 10:13 am

Hello Sharmaji, I read your comments on my post, and understand the same.The counter is versetile in its nature so it could find many application ,In future I will use it as LC meter too by calculating the frequency.That is why I build it a stand alone unit, so it could be use as counter plus other application. Many thanks for the devloper of the counter and ,specially you and mr. niras were very helpful during building the counter.







thanks for the help ,Shailesh.
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