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Thread: Why we designed stuff the way we did

  1. #1
    DIGWDF Engineer member dirknerkle's Avatar
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    Why we designed stuff the way we did

    The DIGWDF Store has been closed for nearly a half-year now and we're still picking up the pieces. But lately, in the process of designing a new display element using a commercial, plastic snowflake from Menard's, we decided to look into our "personal collection" of products we assembled for ourselves because we need five of these new display "PixelFlake" pieces, and we were curious what electronics we already had in the box with the hope to eliminate having to produce any new PCBs or home-etch some. We found some, and this gives us the opportunity to explain a bit about why we designed things the way we did. In particular, this concerns two DIGWDF products, the MiWiFi controller and the RS-485/DMX adapter, both of which use the ESP-01 module and Shelby Merrick's most excellent ESPixelStick firmware.

    Since the PixelFlakes will be standalone wireless units (like all props at Dirknerkle's Lights) we're using a 120vac to 12vdc at 700ma power buck for powering both the electronics and the 12v pixels that will be designed-into each display piece. Our power calculations indicate about 600ma of current is required, so we should actually have a little headroom to play with with the 700ma power buck.

    First, here's a video, because watching video is always more fun than reading a post, right?



    In a pixel mode, the DIGWDF MiWiFi Controller was designed to provide on-the-prop control of a relatively small group of pixels, usually less than 50. It was designed to be a lesser-expensive substitute for the ESPixelStick when only a few pixels are needed or wanted. In the case of these PixelFlakes, there are only 6 WS2811 chips in use which is essentially 6 pixels, although each chip controls three RGB LEDs for a total of 18 LEDs. This is a perfect use for the MiWiFi because it has minimal components and at about one square inch in size, is tiny enough to be unobtrusively built into a display piece. Add a small 120vac power buck of perhaps two square inches in size and in a very small space, you have a display item that's completely portable and mountable almost anywhere in the display where 120vac power is available. This is the ultimate in inexpensive flexibility yet yielding none of the issues of control because for roughly $10, one can easily add pinpoint wireless control to such a display piece. This is what MiWiFi was designed to do and why DIGWDF specialized in these crazy little products.

    The DIGWDF RS-485/DMX adapter solves the issue of making virtually any common DMX controller wireless. Using simple short DuPont connection wires it makes interfacing to a controller a snap -- a convenience that has also always been on the minds of the DIGWDF engineers. (Well, what little minds they had, of course...) And because the adapter has both 5v and 3.3v power regulation, it can be used with many power sources by simply tapping off the controller's DC power input. And with the on-board 75176 differential transceiver chip, the data output is a nice, strong 5vdc data signal of whatever firmware the user flashes into the ESP-01 module as the 76176 works as a voltage level shifter in addition to providing the differential signal (D+/D-). In a pixel mode, only the D+ output is used as the data source for the pixel stream and as the adapter's power can be anywhere from 5-30vdc, power can also be sent to the pixel string by simply attaching the pixel power lines (+/-) to the adapter's power inputs along with the main power supply. For 12v pixels, simply use a 12v power supply and bingo, you're in business. So the RS-485/DMX adapter can be used in some very creative ways -- and still be a lesser-expensive substitute to the ESPixelStick.

    This is why the DIGWDF engineers designed things the way they did: lower cost, smaller size and more flexibility.
    Even though the DIGWDF Store has closed, it's still awesome! Thanks to all who have supported us through nearly 7 years of excitement!
    Parts of the store will remain open for downloading documentation, firmware and other files: http://digwdf.com/store


  2. #2
    Junior Elf member
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    That's just cruel... talking about things you can do with parts you can no longer buy. Sadly, I discovered your store in its final weeks. Or, maybe that's a good thing for the wallet I suppose. I bought a few random things to mess around with and try to learn from. What you said got me thinking of something I could do with the RS-485/DMX adapter. Unfortunately I don't remember if I bought one or not and can't check for a few days... but I did download the assembly manual, so I'm thinking that a good sign. Thanks for making parts that are flexible for a wide range of uses.

  3. #3
    Santa's Helpers Falcon's Avatar
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    asualum2001,

    Keep in mind that you can purchase the gerber files (PCB files) from Dave's website for $2.50 (I think) send them to a board house like jlcpcb.com and get 5 boards for 2 bucks. Dave has also made a huge zip files of all of his documentation.

  4. #4
    DIGWDF Engineer member dirknerkle's Avatar
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    Thanks, Dean. Yes, even though the store is closed, the boards live on through the Gerber and DipTrace design files which are readily available!

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    Here is another thing that we've tried to pioneer over the years, but not many other board producers have followed the concept. We don't really know why others are averse to adding something like this to their boards when it's so easy to add a hole or solder pad here and there along with a label to tell the DIYer what it is. After all, a pad or hole or two certainly doesn't cost any more and it sure doesn't take up much room. We put them all in a row making them easy to find. We've always felt that anything we could do to make it easy for the DIYer was a good thing.

    Click image for larger version. 

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    This is a row of headers on all of the DIGWDF MiniRen controllers, the Renzilla and in many cases, most of our adapters, too. This header provides easy access to some of the most critical circuits on the controller and making these available to the DIYer makes it easier to interconnect things -- or ADD things.

    RX: The RX pin is data INPUT. This connects directly to the PIC's data input pin. Why is that good? Because you can connect the output from most any other controller to this pin (and the ground) and bingo, you've got the two boards talking.

    CK: This is the CLOCK pin. On MiniRen controllers that use the 18.432mhz crystal, this gives you the option to sync one board that doesn't have a crystal to one that does, saving about $3 in cost. It can also be used as a test point to aid in diagnosing a misbehaving AC controller.

    DO: This is data OUT. How would you use this? Well, like the input pin, this also connects to the PIC, except this is the OUTPUT, which makes it easy to link one MiniRen controller to almost any other type. For example, take the DO and ground from the MiniRen and plug it into the D+ input and ground of an RP-8 or SS8 controller and they're sync'ed together.

    ZC: This is the ZC signal that MiniRen A/C controllers have. With this pin, you can connect 3 or 4 other controllers together and share the zero-cross signal across controllers, saving money and build-time. Also, you can use the pin as a test point to ensure the H11AA1 chip is working right.

    G: This is the board ground pin. Whenever connecting two dissimilar boards together, you will always have to make the grounds common.

    +5: This is a 5vdc tap pin off the MiniRen's power section. Having this pin makes it easy to provide power to other 5v devices, such as RS485 adapters and the like or, provide DC power TO the MiniRen from an outside source.


    Want a practical example of how this concept can be used? Well, let's say you needed a 16-channel controller and had a handful of MiiniRen-8 boards sitting on the bench. Easy peasy.

    You'd build the first MiniRen, complete with the transformer, ZC circuitry and crystal and, of course, the JP2 header. Then on MiniRen#2, you'd save about $12 in parts by not installing the transformer, ZC circuitry, rectifier and voltage regulator: you'd simply connect the CK, ZC, G and +5 pins together on both boards and then connect the DO from MiniRen#1 to the RX of MiniRen#2. Bingo. Done!

    Could you do it with three MiniRen controllers and make a 24-channel controller? Certainly. Four MiniRens? Sure, that works too.

    We wish that other board designers would share this kind of thinking when it's really so incredibly easy to do. It helps make things modular and flexible while lowering cost -- all things that are important to the DIYer.
    Even though the DIGWDF Store has closed, it's still awesome! Thanks to all who have supported us through nearly 7 years of excitement!
    Parts of the store will remain open for downloading documentation, firmware and other files: http://digwdf.com/store


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