| T O P I C R E V I E W |
| kivdenn |
Posted - Dec 16 2009 : 10:25:12 AM
Hi all, i got this triangle wave oscilator from http://pcbheaven.com/circuitpages/Triangle_Wave_Generator/ , the author says he built it using a 5v supply but can run on any voltage as long as it doesnt exceed the rated voltage of the OPAMP ICs. I also built it using a 13v supply at 50hz but it gave a funy wave which looks like a triangle wave but has got flat end both on top and the bottom. When I changed it to operate on 5V it gave a good triangle wave at 227.27hz but when I reduced the frequency to 50hz by changing the value of R to 100k the wave developed straight ups and curved downs. I want to use this oscilator on the MSW inverter with stable output but I fear the curved triangle waves might negatively affect the overall invewrter output. For that reason please help try to make this wave a clean triangle wave at 50hz when the circuit is hooked on a 13v power supply. Thanks Dennis
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| 15 L A T E S T R E P L I E S (Newest First) |
| pebe |
Posted - Dec 31 2009 : 04:51:47 AM
Looking at your 'Output at pins 2 and 7 of CD4017.jpg' picture in your earlier posting, the 4017 was not operating correctly then. There should be alternate pulses on pins 2 and 7.
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| kivdenn |
Posted - Dec 31 2009 : 04:25:59 AM
When I changed these caps to 2.2nf, there was no output at all at the output pins of Cd4017. What could be the cause? Thanks |
| audioguru |
Posted - Dec 30 2009 : 10:20:39 AM
Kivdenn,
You said that Chemelec's triangle wave generator works perfectly and showed its output. It is the same circuit as all your other triangle wave generator circuits.
At the CD4017 you used capacitors that are 10nF (103) instead of 2.2nF (222)so no wonder your circuit does not work properly. |
| kivdenn |
Posted - Dec 30 2009 : 09:15:09 AM
Here is the triangle wave generating circuit by Chemelec which I used in place of LMC555. It is not a single op amp its a dual op amp, have a look at its datasheet http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXuxuyv.pdf
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| pebe |
Posted - Dec 30 2009 : 04:42:27 AM
You cannot use a TL082 in place of a LM555. If you are using a single op-amp to generate your waveform then you must be using some other circuit to those shown.
Why don't you give the complete circuit instead of vaguely describing it? |
| kivdenn |
Posted - Dec 30 2009 : 04:28:06 AM
I used TL082 to make the triangle wave generator circuit instead of the LM555 and the TL081 in place of CA3140 which is responsible for varying the out put wave form so as to stablise the output voltage.
Now Guru why do you think made my wave behave like that, because you assured me that Chemelc's circuit can play the trick of generating a good triangle wave? Thanks |
| pebe |
Posted - Dec 29 2009 : 06:18:54 AM
......TL081.....TL082......?
What circuit are you talking about? I see neither of these ICs in any of your circuits. |
| audioguru |
Posted - Dec 28 2009 : 1:21:15 PM
Your "scope" is awful:
1) The triangle wave is supposed to have perfectly straight sides instead of curved.
2) The square-wave is supposed to be perfectly square instead of rectangular. |
| kivdenn |
Posted - Dec 28 2009 : 05:16:31 AM
I have finaly manged to upload the images. Its funny mozila firefox cant upload the images but internet explorer does. Any way here are the PC osciloscope images of the triangle wave output at pin 7 of TL082 and the square wave output at pin 6 of Tl081 and the funny square wave output at the decoded outputs 1&3 of CD4017 which is 25HZ (half the frequency of the triangle wave output of 50HZ at pin7 of TL082) The caps I was talking about are the two caps at the clock and Clock Enable pins of CD4017 IC. Why do you think was the cause of this deviation in the results? Remember am using a PC scope. Thanks Dennis
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Download Attachment: Output at pin6 of TL081.jpg
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Download Attachment: Output at pins 2 and 7 of CD4017.jpg
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Download Attachment: Correct MSW Stable voltage.gif
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| audioguru |
Posted - Dec 27 2009 : 11:15:05 AM
Chemelec's circuit uses only one timing capacitor like most of the other triangle-wave circuits, not two. Ceramic capacitors usually have a very wide tolerance of their value. If you don't know its value then you should throw it away. You should use a 5% film capacitor.
I cannot remember the MSW circuit but maybe the TL081 opamp is being used as a comparator to produce pulse-width-modulation. The TL081 opamp has a problem of "Phase-Inversion" when its input voltage is too close to the ground voltage (within about 3V or 4V). Then its output frequency is doubled. |
| kivdenn |
Posted - Dec 27 2009 : 07:55:00 AM
Hi all, I have discovered what has been failing my circuit I have been using a PC scope and because its maximum voltage is 5V and my circuits have been 13V, there has always been an excess of 7V and that's why my waves have been clipped both at the bottom and top.
However I have used chemelec's triangle wave generator circuit and applied it to our MSW inverter with stable voltage circuit but the results are not what I expected. As you can see bellow the triangle wave generator has worked well and produces good triangle waves at a frequency of 50HZ, this wave is fed into the TL81 OP AMP which converts it into a square wave which is also OK but when this wave is fed into the CD4017 IC the output is a square wave at half the frequency of the triangle wave. I expected to generate a modified sine wave at a 50HZ frequency. What could be the cause of this. NB. for the two 2n2f capacitors i used ceramic caps with these writings 2A103H. The radio shark told me that they are 2n2f but I doubted him, could they be the cause of this failure? Thanks Dennis
OOOPS the images are once again failing to upload MR. Modorator what could be the problem? |
| pebe |
Posted - Dec 24 2009 : 05:12:02 AM
If you are using a PC scope that uses the sound card, don't forget that it can only handle signals up to 5V peak. Any signals greater than that will be clipped by its internal diodes. |
| kivdenn |
Posted - Dec 24 2009 : 04:25:20 AM
As I told you before, that I am going to use this circuit in the MSW inverter with stable out project, the out put of the second OPAMP is going to be fed to a TL81 which will then converter it into a square wave that will in turn be fed to the CD4017 to be changed to a modified sine wave. I think the load resistance component here is the TL081 IC but I dont know its resistance. As for the 100k and the 47k resistors I checked and there was not swapping. Do you think the problem could be with my PC Oscilloscope? What will happen if I use a clipped wave ? Thanks
Dennis |
| audioguru |
Posted - Dec 23 2009 : 2:13:15 PM
The circuit from Chemelec is exactly the same circuit. Its output triangle wave goes from about 4.4V to about 8.6V and since the peaks are nowhere near 0V or 13V then the output is not clipped unless the output is overloaded with a load resistance that is too low, or if the 47k and 100k resistors are swapped.
I asked "what is the output load?" but you did not say.
A TLC555 or an ICM7555 are exactly the same as an LMC555. They are made by many manufacturers.
Here is the same circuit that fades LEDs:
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| kivdenn |
Posted - Dec 23 2009 : 09:58:00 AM
I also got this one from http://www3.telus.net/chemelec/Projects/Oscillator/Oscillator-a.png but it is also producing a clipped triangle wave form at the bottom and top. Do you think the problem with my assembly or oscillator? Thanks and Mery Xmass
Dennis |
