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  1. #1
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    Which knob for the CTS288 encoder?

    I'm going to use this encoder for the OBS, ADF, and XPNDR. Is this a good choice? What knob is recommended?
    John

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    Re: Which knob for the CTS288 encoder?

    The 288 shaft on the ones I bought from Digikey have a .25 inch chaft with a flat side towards the end. Any 1/4" knob will work, I prefer to use only knobs that have set screws. Depending on how authentic your sim is, you can use almost any knob. I am still trying to get authentic knobs for my A320 sim, but it is proving to be very difficult. I found waht appear to be very similar knobs at ECH, but holy cow HOLY COW are they expensive! over $50 EACH! No way I am paying that much. I will buy my own injection molding machine and hire a mold made before I do that. If only I had a rep-rap rapid prototyping machine...... yeah....

    Seriously though I would be fine with any good looking knob if I never find the actual knobs I need. It will be up to you what knob you use. Thesurplus outfits have tons of knobs, as a matter of fact, there are cheap encoder sets on ebay that come with great looking knobs, 2 different styles that I have seen, one that I have bought. They are very usable. If you are diligent in your search I am sure you can find what you need. Digikey and Mouser have all sorts of knobs, as well as all of the knobs that are on ebay. Here is a good looking knob from ebay that domes with encoders to boot:

    http://cgi.ebay.com/12mm-Rotary-Enco...item27b1214ef6

    Note that these are generally NOT grey code encoders unless otherwise stated, and IMHO they are not of the same quality of the CTS 288. I have this batch:

    http://cgi.ebay.com/10pcs-12mm-Rotar...item5191fc7245

    And the encoder works well on Leo's board... The knob is very nice, but a little large for my FCU panel.

    If you are in/near central Florida then Skycraft on I-4 and Fairbanks has a giant selection of very nice knobs for .50 each.

    Buddy

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    Re: Which knob for the CTS288 encoder?

    Thank you Buddy for your very informative reply. The 12mm knob will work well for me. I do have a couple of questions if I may. What is a "gray" encoder? How many detents per rotation do the encoders you're using have?
    Thanks,
    John

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    Re: Which knob for the CTS288 encoder?

    The "grey" refers to the 2 or 4-bit code that is output on the encoder pins when the shaft is rotated. The are many different codes, some simply represent the direction of movement, others can sense speed as well. Still others are capable of very very precise detection, while others are made for more general interface use and don't need to be ultra-precise, but must have the ability to operate in all conditions, such as hot, cold, dirty, humid..... these are all characteristics that must be as robust as possible on consumer products. For industrial, military and aviation products the encoder must have all of these qualities and then be ultra-reliable, with thousands of man-hours between failures. To the extreme, if you were to examine one of the single-pole, single-throw toggle switches used on the space shuttle's primary and secondary power distribution and control systems, you find a toggle switch that looks very much like what you buy from Mouser, but inside it has well over 100 different parts! This is due to not to the need of the switch to be ultra-precise, but it simply must not fail. That's the reason aerospace stuff is so expensive, that and the fact that it is also tested to the extreme. The CTS 288 family is what I refer to as a consumer-grade component, though I feel it is made very well. It has 16 detents and has an estimated life cycle of 50,000 cycles. It;s important to note that 50,000 cycles is not that much, but that due to measurement standards the life cycle must be represented in this way, even though the "post life-cycle" characteristics of interest on a typical mechanical rotary encoder are bushing wear and contact resistance. Since our applications are considered near-zero for mechanical loading on the shaft, bushing wear should be minimal. As for contact resistance, the "in-life-cycle" contact resistance is 100 millohms max, and the "post life-cycle" contact resistance is 200 milliohms, which is negligible in our application.

    Sorry for the long-winded response, with so much fluff around the answer to your real questions, but I love this stuff and it's an area of our hobby I feel I can contribute to more than in other areas... Westozy (gwyn) is the resident mechanical guru, nico is the SIOC guy, maybe one day I can be the electronics guy. (although I think Leo has the crown there!)

    Buddy

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    Re: Which knob for the CTS288 encoder?

    You can never go wrong with an in depth explanation. Thanks for taking the time to enlighten me.
    John

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