Generating pulse wave

With that circuit pin 6 will get a lot more than 0.5Vpp.

Wow, you must really live in the boonies :-)

Anyhow, it's just six inverters in there. You could also use a 74HC04, or a 74HCT00 or 74HC00 wired up a bit differently. If you can't get those I suggest to move closer to civilization :-)

Exactly!!

I know where to get a 74HC04. Could you please tell me how to wire it, in such a way that specifications (0.4 to 0.5 Vp-p) are not exceeded? A little drawing would be wonderful!

Thank you!

On a sunny day (Mon, 27 Sep 2010 20:45:32 GMT) it happened snipped-for-privacy@dico.no (Slater) wrote in :

Yes!

Page 2 says "0.4 to 0.5" but note 3 on page 12 says "0.4 to 5.0 Vpp" and talks about it going outside the GND/Vcc supply rails if the duty cycle is not 50% (due to the internal 1/2 Vcc biasing and ac coupling) which confirms the 5.0 Vpp. Also, the 74HCT04 output is 5.0 Vpp. So that 0.5 on page 2 is a typo.

Must be east of Tromso then :-)

You just plop it in, has the same pin configuration. Looking at the datasheet it appears that the first part on page 2 may not be accurate. Note 3 on page 12 says, quote "The SC input (Pin 6) can be either a sine wave or a pulse in the range from 0.4 to 5.0Vp-p". 5Vpp is what will come out of your 74HC04, or ion reality a few hundred millivolts less but that's fine. The 74HC04 generates pulses, not sinewaves.

So you shold be fine without attenuation. If you ever need to attenuate it would be easy: 4.7k resistor from U3 pin 4 to U1 pin 6, then 560ohms from U1 pin 6 to ground. But I don't think you need to do that here.

You are welcome :-)

How much attenuation will those values give?

On a sunny day (Mon, 27 Sep 2010 21:29:43 GMT) it happened snipped-for-privacy@dico.no (Slater) wrote in :

I am not sure what you want to do, but that will NOT convert your PC monitor's RGB out to S-video. At least not if it not 30 years old. This is because the H frequency for PAL is 15625 Hz, and PCs normally output double that at least. You *COULD* perhaps configure your graphics card for 15625 Hz horizontal and 50 Hz vertical, but it could kill a modern monitor, or the monitor would simply refuse to work.

So hopefully it was for something else :-)

Yes, it's for converting the RGB signal from a videotape to S-Video :-)

Neeerp! For a crystal oscillator you want 74HCU04... note the "U"! ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

I can see November from my house :-)

It's a simple voltage divider, resulting in roughly a factor of 9.4, so a 5V signal would become 530mV. Realistically less because logic chips never do a full swing into any load. But according to page 12 of the datasheet I don't think you need to do this.

Thank you all! :-)

Sure, but tough luck finding one of those in the woods of Norway ;-)

It's not nice and harder on the crystal but a 74HC04 usually works ok for crystals in the low meggeehoitz range.

Huh? What kind of VTR gives out RGB? Is this the SCART connector? Interesting.

It seems the OP lives in Norway. In Europe many VCRs had (have?) RGB, via the SCART-Connector. We still have our old European VCR, to be able to watch some of the classic movie from there. Until a while ago we could occasionally find a foreign movie at the video rental place but that went belly-up.

Harder on the crystal? Use either a smaller cap, or a bigger resistor. ;-)

Cheers! Rich

Then, eventually it oscillateth no more :-)

On Sep 27, 2:57=A0pm, snipped-for-privacy@dico.no (Slater) wrote: > Jan Panteltje wrote: > >I am not sure what you want to do, > >but that will NOT convert your PC monitor's RGB out to S-video. > >So hopefully it was for something else =A0:-) >

Where in blazes did you get an RGB video tape? I've worked in broadcast for 34 years and I've never seen an RGB recorder. Component and composite both in digital and analog but never RGB.

G=B2

On a sunny day (Wed, 29 Sep 2010 21:13:09 -0700 (PDT)) it happened Glenn Gundlach wrote in :

LOL I did a RGB recorder in the early seventies, recorded R G, B line sequential, and played it back using 2 delay lines to get R, G, B back at the same time. The system was called TriPal. Designed it just out of curiosity to see what it looked like (on my home

When we talk VHS, the color recording is done by mixing down the 4.43 MHz (PAL) chroma to about 560 kHz, and superimposing that on the FM modulated BW carrier to the recording heads, using the FM carrier as sort of a RF bias (as in audio recording). On playback the 560 kHz is mixed again back to 4.43 Mhz (I am talking PAL of course). Designed one like that too :-) That means in essence you already have separate chroma, so it is easy to make a chroma output, the whole chroma processing is separate. So to make RGB for SCART the output has to be decoded first in the VHS machine. So one would think that decoding it to RGB, and then encoding it back to PAL with that circuit the OP is talking about, would introduce 2 extra signal processing steps, and reduce quality. But I did not reply in that way, because it is perhaps possible (SCART also has composite out), that the obtained quality would be slightly better with that circuit, because IF you were to grab the chroma from the composite output, and feed that into the SVHS chroma pin, you would also have to lowpass the luminance to get rid of any chroma in that, attenuating many higher frequencies, so it all depends. It would be nice to hear the OPs motivation of why he does it this way. Better would be to find a point in the signal processing of the VHS where to grab the chroma *before* it is mixed with Y. But this may be difficult as in the later generation VHS recorders most if not all was integrated into just a few chips.