MUTR-kit circuit diagram

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Postby Ralph » Fri Feb 06, 2009 8:03 am

Can anyone give me the ratings or a link to the data sheet for the BC348 transistor? For whatever reason, I cannot seem to pull it up on the Internet.

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Postby Steve Anderson » Fri Feb 06, 2009 12:55 pm

Ralph wrote:Can anyone give me the ratings or a link to the data sheet for the BC348 transistor? For whatever reason, I cannot seem to pull it up on the Internet. Ralph


No, neither can I find any data. I'm wondering if it's a 'typo' and should really be a BC548, a very common transistor in Europe. If this has been 'reversed engineered' it might be the markings on the device are smudged or in some other way not easy to read.

The BC548 is ideal in this application, but so are thousands of others.

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Postby AncientBrit » Fri Feb 06, 2009 6:44 pm

Found a link for BC348 pinout here:


http://hamradio.lakki.iki.fi/new/Datasheets/transistor_pinouts/


Cheers,



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Postby AncientBrit » Fri Feb 06, 2009 6:51 pm

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Postby gary » Fri Feb 06, 2009 6:53 pm

I can confirm that it is indeed a BC548 (at least on mine)
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Postby Klaas Robers » Fri Feb 06, 2009 7:32 pm

Yes sorry, it was a type error. I have corrected it. Thanks.

However I know that this transistorchip has been mounted in different housings and had different numbers. The BC548 is identical to the BC108 in small metal can, the BC148 in triangular plastic encapsulation ("lock fit") and the BC848 (?) SMD transistor. And I have seen more housings. So the first number became more or less a "don't care" for me.
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Postby Ralph » Fri Feb 06, 2009 11:36 pm

Thanks to all!

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Postby AncientBrit » Sat Feb 07, 2009 12:20 am

> Klaas,

"So the first number became more or less a "don't care" for me. "

That's what I like to hear. In the true spirit of NBTV experimenting!!


Kind regards,


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Postby Ralph » Sun Feb 08, 2009 5:02 am

Just for the record, my MUTR kit arrived early this last week and I finally took the time to assemble it. Perhaps "kit" and "assemble" are excessive terms, given the fact that the whole project went together in about an hour with no soldering or other complex ( :D ) operations. It worked "right out of the box". I will replace the diffuser, but otherwise will keep it "stock" for demonstations. Overall, very well thought out and a nice project at a fair price.

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Postby Steve Anderson » Sun Feb 08, 2009 1:04 pm

Ralph wrote:.....I will replace the diffuser...Ralph


Interesting to note that almost everyone says that about this 'kit'. Perhaps some feedback to the MUTR might help them.

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Postby Klaas Robers » Mon Feb 09, 2009 2:53 am

Ralph, I can recommend you to replace the red LED by a orange-amber LED. This is better for the brighness. And a second diffuser might help. I wonder how it would be with a diffuser at both sides of the PCB. I think it will help, but haven't tried it.

I don't like the lens. It gives reflections and hardly any enlargement. I use it without a lens.

I experienced the sync to be with a picture standing too low. Rotating the speed pot changes little and when the setting seems ok the disc might loose sync. I experienced with a resistor in parallel to the motor, but should also do this with a resistor in series with the motor.

But I also got a pdf from MUTR of the sync pattern that is stuck to the back side of the disc. Then I could over glue this with some rotation in order to frame the picture correctly.
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Postby Ralph » Wed Feb 11, 2009 6:09 am

Klaas,

I have already installed a better diffuser and will make some other modifications in the next few weeks. I am off that task for the moment and am busy converting the MUTR circuit to a universal televisor pc board. Given how easily the MUTR system fired up, it seemed to be a reliable way to jump start all sorts of televisor projects.

The board is 4 x 4 inches (102 x 102mm) so that nothing is crowded and experimental modifications will be easy. The board uses the IRL530 (or any similar FETs) since, with a suitable heat-sink, that device will run most DC motors. The video portion of the board will accommodate both TO-92 and TO-220 driver transistors, permitting a light sources ranging from a single LED to a large LED array, not to mention an actual neon tube if someone were so inclined. The board is designed so that the LED and sensor for the optical chopper are off the main board, permitting maximum flexibility with respect the the mechanics being used. It will take a week or so to get the board made and I will test it initially using the DE Televisor mechanics. If it works well, and I see no reason why it should not, I will post all the project documentation on my web site.

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Postby AncientBrit » Wed Feb 11, 2009 6:27 pm

Ralph, that's very interesting.

I've just ordered up an MUTR kit so anything you produce will be of use.

One thing I've noted on the motor control is that the drive is single ended from the FET.

Apart from protecting the FET does the shunt diode provide any form of regenerative braking or does the motor "flywheel" when drive is removed?

If there is little regen. braking I wonder whether a bridge drive to the motor would give a more controlled mechanical response and a tighter servo.

Regards,

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Postby Klaas Robers » Thu Feb 12, 2009 1:48 am

Yes Graham, you are right. The drive of the motor is single ended and the diode is just there to protect the FET fore inductive actions of the motor.

I connected a resistor of 12 ohms accross the motor which gives regenerartive braking and I got the impression that the servo works better. However still the disc might catch in one frame shifted, but sometimes also correct. This can be seen with an oscilloscope across the motor.

Then you also see that the reflective sensor has problems with a wobbling disc. Then the distance disc-sensor is changing, giving a varable phase shift of the picked up pulses. And indeed,the disc is not really flat.

I should also do some experiments with a resistor in series with the motor. Pete Smith says that this helps in certain occasions.
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Postby Panrock » Thu Feb 12, 2009 2:28 am

Klaas Robers wrote:I should also do some experiments with a resistor in series with the motor. Pete Smith says that this helps in certain occasions.

Yes Pete recommended this to me too, when I was having problems with hunting. I have inserted a 2 ohm resistor in series with my motor (12v @ around 4A) and this has greatly improved things.

Because my motor takes so much current, it has its own power supply. Originally this was only roughly smoothed. Smoothing it properly, with a power regulator, further reduced hunting. It is now basically eliminated.

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