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AVRFreakMan
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Hi am having trouble getting the parallel port to work and i dont understand why. The radio is working purfect with the potenteomoter but i cant tune the radio with the parallel port. If anybody knws why i would really be happy
Explain more!
Did you use a program? What program?
What OS? My program runs only in plain old DOS environment. That means DOS, Win95, Win98(SE) but not any NT based Windows.
Have you measured the voltage in B point with a multimeter? Does it change in regular steps?(0 to 5V, @ 5V/255 steps)
If you think everything else is correct, check parallel port's settings in BIOS. Alter SPP/ECP/EPP settings and you'll see.
Report your findings and if anyone has any photos, it whould be nice to see them.
Kyriakos -
Found another scan image of the PCB.
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I haven't done any changes in this circuit.
This is my reply in MP's email notification that I got yesterday:Hello Mike.
The circuit is correct. I had to sit back and think of the theory behide the
varicaps for a while and check the real PCB. The result is that the circuit
is correct. Every varicap, like zeners, has to be biased in reverse order,
otherwise it acts as ordinary diodes. If you see, the cathode is DC
connected to the +5V line, via the coil, and the anode is allways connected
to a lower voltage, via the potensiometer.
The PCB is verifying this. The black line in diode's body goes to +5V. I
made it severals years ago and was hard to find it in the pile, but still
works! Here is a foto that I took yesterday with my mobile phone camera,
while I was listening some random radio station.
I used the BB329 varicap in this prototype and works very well.
However, I should say a few more words that may not be obvious.
1) The operation range of the varicap in this circuit is 0..5V. The BB329 works up to 32V but here is used up to 5V. This results in about 40 to 15pF.(The datasheet is wrong when it says VR=3V -> ~3pF. It should say VR=30V -> ~3pF. Check the "Capacitance versus reverse Voltage daigram".) Use a similar varicap.
2) If you decide to use the LPT option, cut the line in point "A", delete the potensiometer and connect the "B" point, to wiper's line. If you leave the pot in, you may use it for manual micro-tuning but it will introduce some unwanted voltage drop of the R2-R LADDER circuit.
3) In my prototype I used the LPT option, without any potensiometer.
Furthermore, I added an op amp connected as a buffer x1 from "B" to "A", just to be sure that the R2-R LADDER circuit will work with my LPT port. However if the pot is deleted, the buffer is not necessary.
P.S.
Dont's ask me for the PCB layout. I tranfered the circuit by hand directly into the PCB. One time job.
Kyriakos
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The idea is doable but I'm not convinced that you have the skills to do it.
You could use a microcontroller with a touch LCD but you can't do that with C++ and Win32 API.
For that convenient programming enviromment you have to use a Pentium board, like those PC104 style.
It is also expandable, by bulding more consoles. One for maybe each room in the house, or in strategic places and for other cars. All these consoles should have passwords and the communication should be bidirectional with feedback/acknowledge.
What kind of RF communication are you up to?
You could do it with free license 433MHz or with your cell phone, via SMS/MMS but this is not free. The cell phone could also be your console and Java builders exist for smart phones.
But first of all, you should start modifying the electrical system in your house, to be remotely controlable.
The whole thing is not going to be cheap! -
Hi BOHDA,
nice to hear that it works.
I followed the schematic in analog section. In my experience, it looked ok. It wasn't ok, that's why it doesn't show stable/correct values?
The PCB is unclear too and I was too lazy to try to extract the schematic from it!
In the breadbording circuit that I made, I tried LC values around those you mention(I found them in comments in the source code) but I had no luck. Maybe it was breadborad's fault. Loosy contacts and stuff..
I'm amazed by the fact that it shows you all the characters in LCD(even separated in two lines). I couldn't reproduce that. In my circuit it shows only the first 8 chars no matter what!
The advice regarding not using the RS485 was in order to keep the circuit free of RS485's spikes/noise or battery's life?
That was the only section it worked for me! :)
Actually I didn't use the RS485 converter, just took the Tx output from the AVR and used an RS232 converter to my PC but I could finally see what the LCD should show!
I don't know if I ever try(again) to make it work.
I'm actuallly looking now for a more sophisticated circuit that whould be able to measure inductance, capacitance and resistance in every component(LCR).
There was such a device(construction article) in ELEKTOR's magazine some years ago('97 ?) and it had a DSP to do the job.
Kyriakos -
Some microphones have three leads, othes have two leads.
One of those leads is surely the ground(or -V or 0V or GND or Common).
Both of these two categories might need supply that take from the third lead, if they have three, or from the second(which additionally serves as MIC_OUT), if they have only two.
For those with 3 leads, the one that is not the VCC nor the GND, it is the MIC_OUT. -
This circuit is a CB transmitter, not "reciever"(the correct spelling is "receiver").
CB means Citizen's Band.
There are microphones that need a small supply voltage(and limited current which is done by the help of the resistor R5) to be able to work(because they have embedded preamplifier). This is why the circuit has this option.
For microphones that do not need this, you can just leave it unconnected.
Kyriakos -
pdmr,
How about this site:
http://www.xs4all.nl/~barendh/Indexeng.htm
It hasn't the BAT29 diode but it has many other RF schottky diodes which might suit your needs.
Look under RF diodes ;-)
Kyriakos -
L2 is the tuning coil.
Just make it: take a thin wire(0,6mm) and make 5 turns of 4mm internal diameter.
If it doesn't work try to stretch/squeeze it and if it doesn't work add/remove turns and repeat.(adding turns reduces frequency).
If no success, check the PCB and components for errors, or use a capacitor trimmer instead of the varicap, or search the internet and the datasheets of TDA7000 for other similar circuits.
Kyriakos -
I gave up!
It doesn't work in any way. Even though I would bypass the LCD because it has a workable connection for a PC COM port, I cannot bypass the fact that it doesn't measure any coil or capacitor. The readings seem random. :-(
Kyriakos -
If it cannot tune to any station, experiment with the coil. Stretch it, add more rounds...
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Thanx MP!
Useful info.
So the 16x1 LCD that I tried is actually from those 16x1A.
I'll test the whole circuit with this LCD in the weekend and see if it's worth the trouble so far.
Kyriakos -
Groovy,
you haven't seen this?
http://www.myplace.nu/avr/minidds/index.htm
Kyriakos -
Well,
the circuit in general is unclear as for the values of many components(L,C) but it is easy to test the digital section without building the analog.
A majore error was in LCD data pins. They must be swaped. Where B0 must be B3(B0->B3,B1->B2,B2->B1,B3->B0). The rest data pins should be pushed gently down to ground.
About the LCD that displays only the first 8 chars, I just used a 16x1 LCD in a circuit that needed a 20x2 LCD. It displayed the first 8 chars from the 1st line and the first 8 chars from the 2nd line in the single line that the 16x1 LCD has.
So I assume that there is some confusion in initialization when you init the LCD for 1 or 2 lines.
I think that if I'll try a 16x1 LCD, it is going to display the data correctly.
Kyriakos
P.S.
>>MP
What do you mean by "16x1A displays"?
The letter "A" defines some special characteristics? -
I've seen this one but its too general. I'll have to combine all these info and experiment a little.
Thanx,
Kyriakos -
Thanks, hotwaterwizard
especially that last txt file seems very helpfull.
Kyriakos -
I don't know where to buy those, I couldn't locate a datasheet either but it seems to be 5V/30mA schottky diode.
What about the BAT85? Its characteristics are much better and you can find them in local stores.
Kyriakos -
Thanks hotwaterwizard,
I had not found the last pdf you found. It's one more clue!
It seems that the Toshiba LCD controller T6963 can control those ICs. I'll have to emulate this controller's signals to see if it can control my LCD in any way. -
I'm looking for the datsheets of these LCD drivers: T7900 and T7778 , both from TOSHIBA.
The T7778A has 100 pins and the T7900 has 92 pins.
They are on a 640x400 monochrom graphic LCD:
HLR1010-10-1101 ASSY HLD1010-03-0010
which comes from an old Macintosh and I'm trying to find how to use it.
Thanks.
Kyriakos -
Anyone tried to build the "LC Metre" from site's New Links?
http://xavier.fenard.free.fr/LCMeter.htm
I breadboarded the logic circuit and tried with LCV100803.HEX(flash), LCEEV100803.HEX(EEPROM) files for the AT90S2313 u-C but the LCD works funny. It displays only the first 8 characters from the messages while they had up to 16 characters. :(
I know it should be an one line LCD and mine was 2x16 but this should not cause any problem. LCD internal character addressing is the same for the first line, nomatter how many more lines the LCD has. I tried 4 different LCDs, 2x16 and 2x20 but all displayed the same.
I'm pretty sure that my connections are ok(the schematic has a few errors but I corrected them). The problem must be on the firmware.
Anyway, I just want to check if it really works as an LC meter and its accuracy is ok. If yes I could spend some time to hack a bit the code and build a PCB for it.
The results so far have dissapointed me. :-\
Kyriakos -
Sorry for that folks.
The original text was in Greek and it did made sence back then. The text in the above web-link was translated to English using a PC translation utility which doesn't understand electronics terms such as Ohm and Farad. :P
As a result the reading and understanding of the text is rather difficult.
Anyway, mF = uF and MW = MOhm.
As for L2, take a 1MOhm/0.25W resistor, and wrap a few turns of 0.5mm (or so) wire on it.
Play with the values if you are not satisfied with the results.
After all these projects are there for you, to experiment and learn.
Kyriakos -
I don't have the specifications for the varicaps. You should find them and check if they have similar capacitance vs reverse voltage curve.
The next step is to play with the coil. There is no need to keep it in form, you can stretch it, pull it, push it, put a nail in it, make it an ugly thing until it works :-).
Ok, don't overact a lot!!!
If it still doesn't tune in FM, try another coil and play with the turns, add or remove one or more turns.
You should find the golden edge somewhere there.
Kyriakos -
24V AC is a standard Voltage Output of common transformers, that's why this circuit was designed for this voltage. A few volts up or down(maybe +-5V) aren't going to produce any fault but it is recommended that you use a 24V AC transformer.
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:) re your capacitance meter project:
1. can this meter measure the "effective series resistance"?
Project Link: http://www.electronics-lab.com/projects/test/006/index.html
No, this circuit cannot measure ESR.
You can find circuits for this purpose if you search the internet. Some of them are offered as kits.
Some months ago(maybe 1 year or so) Elektor magazine published an article including all the schematic, PCB etc of an instrument that could measure ESR onle, not capacitance, but it had easy to find and no programmable components, so it was easy to build. I made one and I am very happy with it.
My advice is to build one. It is very helpfull in finding faulty electrolytic capacitors.
Kyriakos
FM Radio
in Projects Q/A
Posted
You should NEVER attempt to measure resistance in a powered circuit.
Anyway, remove R4 and it should work. You didn't see the scissors?