Narrow-Bandwidth Television Association

gary wrote:Sorry Harry, yes it was 48k. The 48k is more for your benefit than mine whereas the stereo thing is a pain as I have to keep removing the right channel each time I do an analysis - hence my selfishness

Thats good i am starting to get the hang of the program ,i just have to make sure that 48k sample record is set as that if i bring another screen up .

The help on the mono helps too

I did one last test tonight before i put it away , i Tested a LDR and did the head amp sensor test again ,i need to test that at different resistance blocks to the sensor as i mentioned it changes gain ,i just have a trimmer on at the moment .

response graphs:

gary wrote:response graphs:

Thank you Gary just looking at the results ,the head amp one looks pretty steady before a quick drop off at the high end of the sweep.

The LDR has a slight steady fall to the high end ,interesting to see .

I would like to see what the resistance for the photo diode should really be set at.

To day i have been a little distracted looking at a op amp as a head amp the CA3140 just to see ,looking into Steve's advice .

I came across this IR transmit extender circuit ,it says its a CA3040 on the schematic but says its a Ca3140 explaining the circuit.

I just used the first op amp part of the circuit .

http://english.cxem.net/infrared/ir8.php

I had my light sensor with a shielded cable at the start to this circuit but results were a lot of noise pick up ,it was much better with my photo diode soldered right to it .

I did do a sweep test see below ,i am not sure yet what to make of it as its a bit weaker to my other tests,but i also did a NBTV transmit test from my led transmitter to this little circuit then again displaying on the lap top,results were distance wise it was not as sensitive to my other circuit but that could be i am just using a clear Led as a photo diode but i could see it had a better or great range of shades of gray to images when at times i manged to get the distance and levels right .

i also tried different op amp in this circuit but was not as good ,that was the Ne 5534 next best but images not as good very dark .

I found my Mel 12 photo transistor head amp circuit and did a sweep test with it amplified via the head amp and by its self just with the 2.2k resistor and 5 volt power supply .

I again did a NBTV transmit test ,again distance is good but results not as good as that last test with the Led as a photo diode and CA3140 circuit .

I sort think it might be a good idea to hook the sensor one at a time up to the Ca3140 circuit since that gave the best results as a receiver on a NBTV transmit and see if it is the circuit or sensor .

I also looked into a mounting problem i didn't think of .... was how the hell do you adjust the thing in the case ,i had to cut a section out of the case which i will replace ,i also did a bit of rethink of the placement of the circuit board.
I also had the problem of the head amp as i know the sensor leads need to be shorter so this makes it easier for me ,i couldn't do it before as the main circuit board was in the way....also frees up more adjustment movement where the head amp sensors seeing the polygon reflection.

Need to stay on track again got a little diverted again today .

Just to point out Harry that you are getting a lot of clipping with those 2 tests - you need to reduce your level somewhere in the chain - otherwise the response looks good.

gary wrote:Just to point out Harry that you are getting a lot of clipping with those 2 tests - you need to reduce your level somewhere in the chain - otherwise the response looks good.

Hi Gary

Was it both ,i was holding the head amp circuit and it might also have been the samsung volume level to the light transmitter .

I am going to try the Ca3140 with the different sensors and see .
i was just playing around with a large solar cell transmitting NBTV to via that led transmitter no great distance but with no circuit just right to the line input of the laptop it did a good job gives a good picture .

Going off track a little but that was interesting.

Yep both heavily clipped - can post waveform if required.

gary wrote:Yep both heavily clipped - can post waveform if required.

Thats ok i just reviewed them yes i think i had the samsung up to high .

Any case its good to know the photo transistor did ok .
Reason i have also been doing the nbtv transmitting tests i hope is a way to see if i was using the mirrors and every thing was working and such with the optics what the out put of the head amp was like feeding it to the laptop .
I can see results are different with the 2 types of circuits so far ,i sort of think if i get results that way it might work with the mirrors .

I have just been experimenting with The CA3140 circuit i posted a while back and have been testing it with different LEDS and such as photo diodes.

I had been testing different LEDS first with my multi meter then in the circuit the ones i would think were giving good voltage results were dreadful in the circuit and visa versa ...the ones that were half as good or worse were giving great results .

Having a look at the resistance change instead of the voltage might be a better way to test these things ,not all clear LEDs are the same .

I also tested the Me12 photo transistor results were not good but i didn't change the circuit for it so doesn't really count .

I tried the dome sensor Gary had given me a few years back and it was fantastic in this circuit ,so must be good for solar cells sure did work well.

I made 2 of these circuits using the 2 best photo diodes .

I'll do a transmit sweep test and NBTV transmit test on these see how it gos .

I did my tests on the 2 circuits the newer one did better ,but it did have the best light sensor the original photo diode which gave me very good transmit results on the first version of the ca3140 circuit ,so looks like thats that photo diode is the best.

Here are the sweep tests a.wav is the original circuit with a newer photo diode clear LED ? i found ,b.wav is the new circuit with the original clear photo diode .

Sorry Gary i think there is a little over volume at the start of the B wav sweep ,i was holding the circuits the photo diodes are fussy ,both wavs were the best that came out .

All the small pictures were screen grabs via garys big picture ,LED transmitting nbtv to photo diode the original Ca3140 circuit newer photo diode..look ok but it was very hard to get every thing right .

The new circuit in the other photos with first photo diode was easy pessy .

I am moving onto the optics side of things now ,i have changed a few things once again /
Looking at simplifying the optics an idea for more light and looking into that past plan posted below of as few optics as needed .
So unbolted the zoom lens and gave it a go.
I found the little lens for the photo diode still gives focus just move the camera far or closer for image size.
The green line near the photo diode lens is the focused area more than likely need to make the photo diode adjustable to that area .
Time to put it away for a few more days contemplating .

I had been using a slides for testing focus for a while but only in a hand held way ,so made this 5 volt slide projector from an old slide holder case so i have a bit of test gear for the camera .

I figure if you have some thing to focus and a good light level you are half way there , a little easier to than big lamp pointing at a test card .

Adjusting the light level to the side might be a good way to set up the camera as well .

I want to make one or 2 NBTV test card slides for this .

Anyway i will do some testing with it tomorrow.

Happy with the progress today ,i have tested the optics with my little side projector .

I made a little test card to start off simple ,i have posted some pictures up and a Gif to show how the movement of the scanning would go sweeping across the photo diode ,seems workable now .

I have some thing there to scan with a nice amount of light but who knows it might just bite me on the bottom again that i have over looked some thing .

Close to a test once i mount the head amp again.

I am posting a few sync tests i did a test run today and i am thinking i still need more amplification on the head amp .