Moderators: Dave Moll, Steve Anderson
gary wrote:Harry I haven't the foggiest clue - it's interesting though. if you played music through it you would get a nice echo effect Maybe it's the ghost of Elvis?
All I can say is I hate laptops.
Harry Dalek wrote:OK Gary i think i have got it .
i swapped over to my other lap top with a line input jack and funny enough its got controls to adjust a range of settings on audio and it was set on generic and i got that ghosting as before on my other computer ..once i set it to none all was fine so was not the cable i was thinking ...
BTW whats the prometheus line rate setting been having a look at the controls you have put in ?
gary wrote:]
Aha that's better.
You can see the spec for Prometheous in the Video2NBTV format window - it it isn't there move this file (after unzipping) into the vide2nbtv program folder:
The format is actually generated on a raspberry pi.
More info here: viewtopic.php?f=10&t=1760&p=15895&hilit=prometheus#p15895
and here:
https://www.youtube.com/user/monroelkjr/videos
Harry Dalek wrote:
Now i have worked out your NBTV player recorder it will be used i will try it on the camera soon its a lot easier than the audio recording software .
gary wrote:
Well if it proves to be useful I am pleased.
Klaas Robers wrote:Today I received the new Newsletter and in it Karen Orton writes that her optical proximity detector gives a sine wawe rather than a square wave. So this looks to be normal. Then it is useless to extract a sync pulse from, too uncertain. However to use it for speed control might use as the mechanical system is too slow to follow the jitter in the optical output pulses.
So Harry, nothing unusual with the optical read out. If you want to know more, ask Karen. The MUTR NBTV monitor also uses this optical sensor and PLL servo for speed control and it works.
Klaas Robers wrote:Today I received the new Newsletter and in it Karen Orton writes that her optical proximity detector gives a sine wawe rather than a square wave. So this looks to be normal. Then it is useless to extract a sync pulse from, too uncertain. However to use it for speed control might use as the mechanical system is too slow to follow the jitter in the optical output pulses.
So Harry, nothing unusual with the optical read out. If you want to know more, ask Karen. The MUTR NBTV monitor also uses this optical sensor and PLL servo for speed control and it works.
Klaas Robers wrote:You are right Gary, but what if the comparator shows some form of oscillation on the moments that it should switch from low to high, or reverse? What if some intereference is on the slow sinewave input signal, or some other noise? Then the comparator might give not just one transient at the time, but one (or more) pulses at the transient time. These are very difficult to capture, but the 4046 might react on it. The phase comparator is a strange counting circuit, I don't know what it does under these circumstances. See a double pulse?
I see in the circuit diagram of the MUTR-kit that they use a Schmidt trigger in stead of a comparator, a high ohmic resistor from the output to the + input. I cannot find the isolated circuit diagram back in my computer, but I still have the chapter 11 in the NBTV Handbook, where it is published.
Steve Anderson wrote:Chasps, It's often preferable to have some form of positive feedback around a comparator to stop this errant behavior. As Gary says this turns it into a Schmitt-trigger. The advantage with something like an LM311 is that you have complete control over what levels you wish the output to change state, from hi-to-lo or the reverse.
I can certainly make a suggestion, but I will need a circuit of how it is currently configured showing the input source(s) and load, as well as the signal level(s) being fed into this stage. Max pos, Min neg.
Often you don't need to use a 'proper' comparator, depending on what it's feeding and the speed required, even a 741 can be used. There's not a great deal of difference between them, except that a comparator usually has a logic-compatible output (311) and is never used with negative feedback like an op-amp as it's unlikely to be stable. (There are always exceptions though).
Indeed, Gary's link to the MURT device shows a LM324(d) used as a comparator, note the resistor from the output to the non-inverting input (+). This is positive feedback which is required to get the fastest and cleanest switching required.
Harry, post the circuit and I'll have a look.
Steve A.
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