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  • claudiosousa commented on claudiosousa's instructable Globe Persistence of Vision1 year ago
    Globe Persistence of Vision

    Absolutely, that is what I tried to explain in the previous post. Then only the relevant data needs to be sent to the controller, and not the whole image.If I was to redo the project,I think I would have the ESP8266 microcontroller. I've been playing with it recently with very good results. Native wifi , 80/160MHz clock and much more flash memory available.

    I live in Switzerland, where I'm not aware of such restrictions.The only restriction I was aware of was that they would not ship it through airplane.Bought my in France, as a private person, from a Mercotac reseller, Cavotec RMS S.A.SZ.I. Les Béthunes16 Avenue du Fief95310 Saint Ouen l'AumôneFRANCENot exactly easy, and had to make it deliver at friends house that lives in France.They have other reseller in other countries too.

    You are right, an Instructables with all the information would have been much better, but more time consuming as well... I thought an incomplete one with images would be better than nothing at all. But I will gladly answer what questions you may have.I'm very interested about your idea of rotary transformer to transmit power and data! We had thought about such a solution, but we had some concerns: - we need to draw 15W at the center, - we were concerned that differences in power drawn at the center (depending on image show, communication,etc) would cause immediate angular speed variationsIn your experience, do you feel that we could have drawn that much power, and expect no variations in angular speed?About the Arduino C overhead, I don't agree with you that it has to be a bad thing. I...

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    You are right, an Instructables with all the information would have been much better, but more time consuming as well... I thought an incomplete one with images would be better than nothing at all. But I will gladly answer what questions you may have.I'm very interested about your idea of rotary transformer to transmit power and data! We had thought about such a solution, but we had some concerns: - we need to draw 15W at the center, - we were concerned that differences in power drawn at the center (depending on image show, communication,etc) would cause immediate angular speed variationsIn your experience, do you feel that we could have drawn that much power, and expect no variations in angular speed?About the Arduino C overhead, I don't agree with you that it has to be a bad thing. It is certainly a big plus that so many people can easy program a micro-controller. Having a slightly more high-level language, hardware independent, and so many available libraries makes microcontrollers accessible to many.That said, I agree with you that when you want speed, you don't want arduino to get in the way. And you can do just that! I've never used assembly, but you can code in low level C using the microcontroller registers directly. In this project, we used a microcontroller having 2 full 8bits GPIO ports available. The shift registers used were divided in 16 parallel lines (2 port of 8 bits each), and I've made the low level bit bang code to serialize the data to the SR. Basically, I just write 1 byte to the low level port at the cpu clock.With a micro-controller running at 20MHz clock, we achieved a 8bits GPIO port refresh rate of 2MHz, that makes 2MB/s. That was enough to handle the display of 648'000 LED/s (30 frames x 120 horizontal steps x 180 leds) and we still had enough CPU available to handle real-time wireless communication. See the SR bit bang code in github (https://github.com/claudiosousa/PersistenceOfVisio...) and the refresh rate oscilloscope image atatched.About the slipring, yes it was from a Mercotac reseller, and here are the price details:1x Slipring coaxial type MERCOTAC 205HS – Code LM02-0205H-S0 – P.U. : 65,80 €. H.T. – TTC = 78,96 €.205-HS 2x4 A, 3600 rpm, 200 MHz, 2 conductors, high speed, stainless steel bearing1x Connectors two contact – code LMX2-00592-00 – P.U. : 14,15 €. H.T. – TTC = 16,98 €.Receptacle -2 wires, 6"1x Connectors two contact – code LMX2-00595-00 – P.U. : 8,80 €. H.T. – TTC = 10,56 €.Cap -2 solder lugsFrais d’expédition / Freight : 35,25 €. H.T. - – TTC = 42,30 €.TOTAL TTC 20% = 148,80 €. (euro)

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  • claudiosousa followed 3D Printing, Survival, Websites, Electronics and 6 others channel 1 year ago
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  • claudiosousa commented on claudiosousa's instructable Globe Persistence of Vision1 year ago
    Globe Persistence of Vision

    That picture shows the case up-side-down (useful to upload new firmware during development phase).So that white box you see on top of the case, is actually the base of it and was later painted in black to reduce reflection.You can see it on the other pics, like this one:

    Thank for your praise. Very encouraging

    Very good question, that was one of the tough problems to solve.The signals was easy, we used the nRF24L01 to communicate between the stationary arduino in the base and the microcontroller in the rotating area.To transmit power, we thought about several options: induction, a generator creating energy from the rotation, etc. Finally, we found an easier approach, we used a rotary connector that uses mercury (liquid metal) to pass the current. In the rotating are we are only using 5v, but because the connector current is limited to 3A, we transform the voltage to 24v before sending it through the rotary connector, and then we use a couple of step-down voltage regulators to get the 5v.Bellow you can see the nRF24L01 in the rotating PCB, and some images of the mercury connector

    Any image with the right resolution and can be used, but it is limited to the 8 colors used (2³).The device is actually controlled by an android app. We can control the device (start, stop, change the rotation speed) and the image itself : (the rotation direction and speed of the image and upload a new image)You can see in the videos a demo where we upload different images and play with the different possibilities.In its current state, an image takes 1-3 seconds to be uploaded and displayed. While this delay can certainly be improved, the low frame rate is not fit for video data stream.A project we have in mind that relates to what your were suggesting is to show on the globe some states (weather, unread emails, stocks values, etc) but those states are obtained in text by the glo...

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    Any image with the right resolution and can be used, but it is limited to the 8 colors used (2³).The device is actually controlled by an android app. We can control the device (start, stop, change the rotation speed) and the image itself : (the rotation direction and speed of the image and upload a new image)You can see in the videos a demo where we upload different images and play with the different possibilities.In its current state, an image takes 1-3 seconds to be uploaded and displayed. While this delay can certainly be improved, the low frame rate is not fit for video data stream.A project we have in mind that relates to what your were suggesting is to show on the globe some states (weather, unread emails, stocks values, etc) but those states are obtained in text by the globe and it is the actual microcontroller that updates the image that it is showing depending on those text feeds.For instance, it would display the sun/rain image depending on the text information about the weather forecasts.

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  • claudiosousa commented on claudiosousa's instructable Globe Persistence of Vision1 year ago
    Globe Persistence of Vision

    http://www.pcbway.com/Good and cheap

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  • claudiosousa commented on claudiosousa's instructable Globe Persistence of Vision1 year ago
    Globe Persistence of Vision

    I've added a step 3 to this Instructable to describe those PCB's more in detail.In summary, we designed adapter PCBs to host the constant current shift registers that drive the leds. The SMD shift registers were soldered into those PCBs along with their components (cap + resistor). They were tested independently and plugged into the vertical bands PCBs.We also had designed a version of the vertical PCB bands where the DIL version of the shift registers are soldered directly, but those bands were larger and we would have had to solder in both side of the PCBs (LEDs on one side, and the components on the other side).

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  • claudiosousa commented on jessyratfink's forum topic Call for contest judges1 year ago

    I would be happy to judge the Tech, Outdoor and Play categories.

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  • claudiosousa followed 271828- and lagsilva1 year ago
  • claudiosousa commented on claudiosousa's instructable Globe Persistence of Vision1 year ago
    Globe Persistence of Vision

    These led strips are amazing to use in projects, easy to use, and handle much more subtle colors (24 bits colors definition).In this project however, it would have been impossible to use the WS2812 (the chip in those LED strips) because of the speed at which we need to refresh each individual led.In fact, each second, we are refreshing 648'000 LED (30 frames x 120 horizontal steps x 180 leds). In other words, we are showing 3600 frames/second (30 frames x 120 horizontal steps).The documentation for the WS2812 gives some details the refresh rate: "When the refresh rate is 30fps, low speed model cascade number are not less than 512 points, high speed mode not less than1024 points". These numbers are too low for our requirements.A bit more information on how we could handle such...

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    These led strips are amazing to use in projects, easy to use, and handle much more subtle colors (24 bits colors definition).In this project however, it would have been impossible to use the WS2812 (the chip in those LED strips) because of the speed at which we need to refresh each individual led.In fact, each second, we are refreshing 648'000 LED (30 frames x 120 horizontal steps x 180 leds). In other words, we are showing 3600 frames/second (30 frames x 120 horizontal steps).The documentation for the WS2812 gives some details the refresh rate: "When the refresh rate is 30fps, low speed model cascade number are not less than 512 points, high speed mode not less than1024 points". These numbers are too low for our requirements.A bit more information on how we could handle such a refresh rate: the main reason we choose to use the atmega1284p was actually the number of available 8 bits GPIO ports. We are actually using two 8-bits ports to serialize the data to the bands, each bit is connected to 3 chained Shift-Registers. So, to do a refresh in both bands, we simply write 24 bytes in each port. (+ the clock handling + the latch bit).

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