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DELETED (Inactive)
27 Posts |
 Posted - Jun 09 2003 : 10:38:36 AM
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appreciated my friend. i will do so and get back to you later. many thanks
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DELETED (Inactive)
27 Posts |
Posted - Jun 09 2003 : 1:28:27 PM
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I have removed R1 R2 and R3 and replaced them with only one resistor 3.2M.
When I connect and disconnect the phone line I can see the LED “glowing” or “emitting” changes but it is very hard to be noticed. So there is some progress.
When the phone line connected .5V on G and .579 on S of the MOSFET
When it is disconnected 7V on G and 0V on S
I also have connected Q2 base to Q2 emitter
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 09 2003 : 2:30:34 PM
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connected Q1B to Q1E with resistor, right?
and, if you use just one resistor instead of R1-R3, where did you connect a capacitor C1 Parallel to diode? that should be fine, just do it.
You may have some oscillation which you can see with the oscilloscope only. That explains most weird behaviors in analog circuits.
Or, maybe, Q3 is damaged. I would guess that at 0.5V it should be closed.
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DELETED (Inactive)
27 Posts |
Posted - Jun 09 2003 : 4:04:42 PM
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]You know what YS , I almost give up from this circuit, I might look for another solution. Like I was thinking of having LED either ON or off whenever the line is busy. Then I can take this output to some gates like counter and display it on seven segments.
This will tell the number of call happen on this line and if the counter does not move that’s mean something wrong with the line. This might do the job as the number of call we get on these lines on a daily basis is a lot. So the challenge now is how to have the LED indication ON or OFF when the line is busy or a call has come. What do you think?
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 10 2003 : 09:25:36 AM
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Khalifa,
If the scope is a problem - well, in electronics it is hard to go without it.
The busy line indicator is also a simple project: all you need is to detect presence of current of 20-30mA. You need actually to cut the phone line and insert a small detector. Simplest thing would be a bridge rectifier loaded with LED part of optoisolator (like 4N35). The output part of optoisolator (with extra pull-up resistor) may be connected to counters, lamps and so on.
But - why to give up? You just started.. just experiment with Q3 first, as was discussed. Then, as you get it working, add other parts. It is quite usual in electronics to spend more time than was originally planned, so do not blame yourself. So far everything with your project goes quite normal :)
Good luck, YS
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DELETED (Inactive)
27 Posts |
Posted - Jun 10 2003 : 6:24:02 PM
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Thanks YS for encouraging me. I found another circuit that I built today and it worked. Please check it out and give me your feedback. It is under http://geocities.com/SiliconValley/Haven/1079/phonbusy.htm
The only thing that I did not like is the LED’s are not bright enough. I might play with the resistors to drive more current to the LED’s. I will try it for one more day, then I will think of having a counter. As you have suggested, this circuit is close to your solution, it is using a bridge rectifier. Thank you Body. I will Update you with the progress and if you have a simple circuit for a counter please let me know.
One more favor, and if it is not against your forum policy , appreciate if you can remove the part in the where I mentioned why I need the circuit for, it is a bit embarrassing.
Many thanks
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 10 2003 : 7:04:58 PM
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Khalifa,
this circuit is very similar to what Aaron has on this website, if bit the same one. LEDs can not be very bright for a reason - the circuit is powered from the phone line and a significant current can not be drawn - especially in on-hook mode. If you draw about 10mA for LED, than line may go in off-hook condition.
But, if you change these two LEDs for opto isolators (4n35 or equivalent), you can use the signal on the other side as you wish. Just use high-value load resistor like 100K on the other side and the current through LED should be enough to drive phototransistor.
Then you need event counter. Use http://www.aaroncake.net/circuits/counter.htm or something like that. Or just a ont-transistor amplifier and bright LED..
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Jun 11 2003 : 09:28:13 AM
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Hmm, that appears to be exactly the circuit and text (copied word for word) from my site. I see that there aren't any credits to my site either...Nice. 
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DELETED (Inactive)
27 Posts |
Posted - Jun 11 2003 : 4:20:20 PM
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I am sorry guys blame it on the NET.
Anyway I have built the counter so far nothing comes on the display. Maybe because I am doing something wrong as usual. My question is , if I use +5 volts as an input to pin 14 . like touching the pin and removing the voltage, shouldn’t I get one count ?
Do all the displays require 5V to work. As the one I have has 10 pins and I think they go like this
1= ground 2= f 3= g 4= e 5= d 6= decimal point 7= c 8= b 9= a 10 = I don’t know what is it for.
The way I came to know these pins, I have connected the ground to pin 1 and moved 5 volts on each pin till I identified them all except for number 10.
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 11 2003 : 11:54:10 PM
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Aaron: sorry, but this website has copies of all your schematics..
Khalifa: what means "nothing on display"? is it totally dark or does it always show zero? Bu the way, when you touch the input, you actually induce a series of pulses there and counter should count them all - and nobody knows how many of them. That is called "bouncing", I beleive. if you use manual switch at the counter input, always use debouncing circuit - and the simplest is just a capacitor. That's for information only. Display should change somehow, I think.
As for displays: 7 pins for segments, one for decimal point, one - common electrode and one is empty, that's all right. But: common electrode can be either cathode (connect it to ground) or anode (connect it to +5). Voltage does not matter, LEDs are controlled by current, so just change resistors. But you mentioned common pin going to ground, and this schematic requires common anode. That should match decoding IC. Maybe this is a reason yours does not work. Please check - and good luck. :)
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DELETED (Inactive)
27 Posts |
Posted - Jun 12 2003 : 12:50:24 AM
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]Thanks YS, I will try this.
Now The idea of having the counter so I can link it with cut phone line detector circuit . I have bought the 4n35 but have not test yet. Appreciate if you just tell me more about how should i connect it, and from which point should I take an input to my counter circuit. The idea of the counter to counts how many times the line got cut. Tahnks
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 12 2003 : 7:11:46 PM
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1. connect diode part of 4N35 instead of LED
2. Connect collector of phototransistor to +5V
3. Connect emitter to ground via 100KOHM resistor
4. Connect emitter and resistor to counter input
Now, when LED is dark, emitter votlage is 0. When LED is lit, emitter voltage is close to 5V
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DELETED (Inactive)
27 Posts |
Posted - Jun 12 2003 : 8:03:39 PM
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Hi YS
I am a bit confused here between points 3 and 4…can you please clarify them more for me. Also, if I connect the 4n35 instead of the LED, can please tell me where should I connect the LED.
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YS
Nobel Prize Winner
USA
1132 Posts |
Posted - Jun 12 2003 : 11:37:17 PM
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connect optoisolator's diode (pin1 = (+), pin2 = (-)) in series with LED or instead of LED.
leave pin3 and pin 6 open. Pin 4 is emitter, pin 5 is collector.
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DELETED (Inactive)
27 Posts |
Posted - Jun 13 2003 : 6:29:06 PM
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Hi YS
I am doing fine so far, the only problem I have, when a call comes. The 2 LED flashes and that is normal but my display keep dancing and I loose counts on the counter. I tried to isolate the 2 circuits grounding “ my LED indicator circuit and my counter” , but when I did that my counter stopped counting.
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cut phone line detector
