Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:Yes, they look generic copies of the DAC-08 and the other flavours of it, so they should work fine.
Well done finding the datasheets, even in Russian you usually can 'decode' them, it's not a novel.
I'll PM my address...
Steve A.
Steve Anderson wrote:The problem with the 4060 is that it doesn't have eight adjacent flip-flop outputs available because Q10 is missing. Also the oscillator needs to run at much higher frequency due to Q0, Q1 and Q2 also being missing. The 'HC4040 is a much better bet having all 12 outputs available. It of course needs a separate oscillator but that's easy with a good old 555.
A note on the DAC-08 (or whatever), although you may run it off +/-12V supplies, the inputs are 5/3.3V compatible. Pin 1 determines what voltage the internal logic switches at. With pin 1 grounded it switches at 1.4V (two diode drops), so it interfaces perfectly with 5/3.3V logic. If you were using 12V logic you would apply about 4.6V to pin 1 making the switching voltage 6V. A very useful feature. Here you just ground pin 1 (as I have done).
I need to sketch up the changes for this timebase use so don't go building anything yet.
Steve A.
Forget the 555 idea...I may have a simpler and more flexible solution. Be aware that here I'm still thinking in terms of powers of 2, i.e. 32/64/128/256 lines. Anything else adds complexity.
Steve Anderson wrote:With the combinations of line quantity and frame rate you'll be needing the slowest, i.e. 32-lines at 12.5Hz, 400Hz line-rate, up to 256-lines at 50Hz, 12.8kHz...and all those e in between. Not a huge amount and quite do-able. 12.8kHz, 6.4kHz, 3.2kHz, 1.6kHz, 800Hz and 400Hz. You've generated them all already! Plus the three frame rates of 12.5. 25 and 50Hz.
What we're doing here is taking on a suitable and consistent ramp generator whose amplitude remains the same whatever the combinations are. So no twiddling of knobs or flicking switches to fill the screen. Being potentially a mechanical source of video I've shied away from the crystal idea as you will need the the ability to match the slight 'off'' rates sometimes encountered.
Now 256-bits at 12.8kHz requires a clock rate of 3.3MHz approximately, a 555 isn't really up to that. So I'm considering the VCO section of a 4046 for this, such you can adjust the clock say +/-10%, maybe +/-20%. The rest of the 4046 would be unused.
[/quote]This obviously is not locked to the incoming video, that's where the MR line(s) come in.
More as I think on this....
Steve A.
Harry Dalek wrote:MR lines Sorry Steve ?
Steve Anderson wrote:Harry Dalek wrote:MR lines Sorry Steve ?
MR - Master Reset input to the 4040(s), pin 11. At first just to test the whole thing out these will be at 0V, later they'll be driven by sync pulses resetting the counters to start of line/frame.
Steve A.
Steve Anderson wrote:You might be needing more than one additional 4040, I suggest you order 4, they're always useful to have around. I think this will require a total of three 4040s.
Steve A.
Steve Anderson wrote:Because of the speeds involved this all has to be HC, CD/HEF is way too slow even when used at 12V, at 5V it's positively sloth-like. I really don't understand why people still use it.
Steve A.
Steve Anderson wrote:I have found the same in terms of speed variations between manufacturers, including HC logic. I have two bunches of 74HC4046s here, one batch from Philips/NXP, the other Fairchild. The Philips/NXP versions with work quite happily up to 25 or so MHz, the Fairchild versions, you're lucky to get 10MHz.
The interesting thing is this agrees with their respective datasheets, the implication is that not all chips of a certain species are created equal.
Steve A.
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