Programming PIC 16F628A

I purchased three of these frequency counters on eBay and  they seem to be  accurate enough for my product.  they run for about 10 seconds and they turn off and then they blink for half a second every five or eight seconds. 

What can I do to have them stay on permanently? 

Brian

Hi Brian,

I found that there needed to be some termination on the crystal input when not in use. For this purpose I plug a 1 nF cap into the crystal socket. If you aren't going to use the crystal tester you could also just decouple it from the circuit by removing the capacitor that ties the crystal oscillator to the input of the PIC.

Let me know if this doesn't correct your problem. If you have three units all doing the same thing there must be a systematic problem.

John

Hi John, 

Thanks for your response.   I went from 1 nf to 15 pf and the counter went bonkers. 

68 pf was the only value made it steady.   Even the first time I tried 68 didn't work.  

Now it seems steady as a rock and the frequency is right on.   But from what I've seen how do I trust it if I get this in the field.  I always thought that there was a timer that I could turn off in the circuit .    The second counter the frequency was off by 30 or 40 Hz and nothing helped.   I guess I can start changing values of those small capacitors. The tuner is such a small range that doesn't mean a thing.  Is there a schematic of this counter?

Brian

Sent from my iPad

Hi Brian,

Here is a block diagram that I made for the counter, assuming that yours is the same as mine.

Referring to the original circuit diagram the 1 nF cap ties the Crystal Oscillator to the input of the PIC. If you do not need the Crystal Oscillator in your application I would just remove the 1 nF cap from the circuit.

This circuit was originally designed by a German Ham Radio Operator Wolfgang Buscher and subsequently hijacked by the Chinese for the little kits we are all enjoying. I had contact with Wolfgang when I was working through the bugs and functional problems that I was having. He is a great guy and didn't hold any malice towards the Chinese. If you google him or check out this address you can get more information on the original design.

http://www.qsl.net/dl4yhf/freq_counter/freq_counter.html

John

The 1 nf is where the test xtal goes, right.  68pf made it stable on.   But the other board is bonkers.   I'll try Wolfgang also.  Thanks,  Brian

Sent from my iPad

I couldn't find a way to contact Wolfgang.  Also The link below you gave me doesn't work.

Brian

Sent from my iPad

Hi Brian,

The first link I put up didn't work so I edited the post and put up a working link. Make sure you are using the one that is currently displayed on the forum not the one that may have come with your first notification.

John

Hi Brian,

The first link I put up didn't work so I edited the post and put up a working link. Make sure you are using the one that is currently displayed on the forum not the one that may have come with your first notification.

John