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Driver Chips and DMX bus termination When searching the internet you can see several chips being used to drive a DMX communication. They all are made to convert logic-level signals (LOW & HIGH) to the EIA-485 differential signal levels on the twisted pair cable. Very common are the chips from MAXIM that I also use for my implementation. The one I ...


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Basically RS485 is a description of a bidirectional communications hardware interface in which devices speak a known, but adjustable baudrate and byte/character encoding is very similar to RS232. How you could send data-packets is described in versions or adaptations of the standard, but it's not very strictly adhered to. RS485 is commonly 2 wire for ...


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I'm doing that very thing in a project I'm working on right now. I can't take credit for this, but it sure has worked well. Both the MAX485 and MAX481 should work well. I modified this design a bit. This design currently has a 133ohm terminating resistor between pins 2 & 3 of the DMX connector. This is used to terminate the end of the dmx bus. I added a ...


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Nothing jumps at me right away from the complete schematics. The bus is properly terminated and failsafed. No path for 12V to make it to the bus or stuff like that. To answer your questions: I think the culprit is the unfortunate combination of chosen power scheme, those GND resistors and suppressors. Multiple rectifiers and long power lines created common ...


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Nah, don't listen to the naysayers. Actually, I can figure out a lot from the information you've provided. And the high-res images were very helpful. My attempt to answer your questions: 1) Can the power needs of the board be determined by visual inspection? Answer: Mostly. Googling for "stepper motor ic 24 pin" led me to find that U2 is probably an Allegro ...


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Wiki says: - DMX512 employs EIA-485 differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. It is unidirectional. So you need to use RS485 interface chips. The fact you have got it working without a 485 interface chip is pure luck but, if you try and transmit any distance without ...


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In the left bottom PCB there is a QuickBlow fuse, but in the original link it is a SlowBlow. I don't have these; will this be a problem? That depends on the inrush current of the AC/DC adapters and the nature of any line faults your device might experience. Generally, as long as the inrush current isn't sufficient to pop the fuse every time you turn the ...


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From your description of what you do, it sounds like you interact with the paying public, so are subject to the full force of public safety, liability, elf'n'safety etc. From a safety point of view ... A LED bar that is specified to operate off 12v to 30v DC is probably not rated to operate at other potentials. If you connect several in series, then some ...


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DMX512 is the standard defining both Physical and Logical layers of the protocol. The Physical layer is pretty much RS-485 as is, with some minor additional allowances. The Logical layer is defined on top of it and has nothing to do with RS-485 specification.


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RS485 clearly specifies a network topology without stubs, well except ones few milimeters from connector to the transceiver IC. So it is up to you to decide. I would like to suggest you to use additional 2x6m = 12m of cable and eliminate the stubs, afterall 250 kbps isn't a slow speed.


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Classically, if you can HIDE the reflections within the rise and fall times, then you have a robust system, IF you have some hysteresis. With 4 microseconds SYMBOL (NRZ, at that) time, will you set up the link for 3 microseconds Rise and Fall times? and hysteresis at 25% and at 75% of the full scale swing?


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You need: 512 channels of high-current PWM driver; Some means of configuring any/all of the channels on the fly; Some means of communicating with the configuration device. If you can find a multi-channel high-current PWM driver with a serial control interface then that would be a good start (because you could eliminate the FPGA's). Failing that, to me, ...


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So turns out that that family of PICs has an ADC module that automatically takes priority over any other components and prevents pins from causing interrupts until it is disabled. Added some disable code to the main hardware initialization function to disable the ADC on all pins and it works a treat now.


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The opto-isolators are after the MAX485. Between MAX485 and the μC. The diagram is from the app note Using Isolated RS-485 in DMX512 Lighting Applications. The architecture with opto is described. At the same time, Analog Devices is trying to push their ADM2487E magnetic coupler.


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Here is the design process I would follow: First, get an idea of the max total supply required: here 30W * 16 COB LEDS. This makes about 500W. We can easily find such supplies off-shelf, however is very difficult to design such an AC-DC power supply at a DIY level. So, we make it simple: use a single power supply for the whole project, that we buy from ...


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Generally electrical shielding only works if it is connected to ground (the ground of the stuff its supposed to shield) and the shields of the connectors are connected to the screens/shields in the cables, if they are not connected to signal ground then they do not work to shield the signals properly, but they do not have to be dc-connected you can connect ...


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Not possible. Your audio card has DACs that run at a maximum sample rate of 48 ksps, possibly up to 192 ksps if you have a really expensive professional card. At 48 ksps, the maximum frequency you can synthesize is 24 kHz. I suggest looking at this libary: https://pypi.python.org/pypi/dmx/1.0 . It is a python interface to a standard USB to DMX bridge ...


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Your callback blocks the system for too long during the time it runs, and the interrupt is not made re-entrant. Normally these callbacks are used to quickly set a flag, prepare for next transmission or something similar so the interrupt is done before the next byte arrives.


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A typical certification / commissioning test sequence for consumer electronics usually includes the following: Usage tests Functional test (test each function / mode) Performance test (test how the device performs under maximum load) Power supply tests Power supply variations (test with minimum / maximum voltage) Power supply failure (test where the ...


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Plastic enclosures generally are not good for devices with high-speed network signals (they do not provide shielding) and for devices with sufficient heat radiation (they block heat dissipation). As it happens, your splitter is both. At the very least make many thin (2-4 mm) vertical slots in the sides of the enclosure and cover them from the inside with ...


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Most uarts handle this just fine, but even if you have some shonky crap that doesn't, just tie the data line from the RS485 RX to a counter/timer trigger input and set the timeout to 90us or so, break detected, then spin in a tight loop until you see the 0->1 transition and reenable the uart during MAB. Seriously, DMX is EASY, for all that writing a ...


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I've been trying to modify them too(older model). I have been trying to use a ESP8266 to change the leds so I can make an app for it, however, it didn't work out. This is what I've researched until now: the two IC's is a LED driver and a receiver. The number on the driver doesn't seem to "exist" when you try to search it up. The receiver, however, is a ...


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DMX needs a cable with 110 Ohms impedance, and it should be twisted. I was not able to see the impedance of your proposed cable in the datasheet, but I doubt that it is 110 Ohms. Another thing is that this cable has only 2 conductors, that means the shield/screen has to be used as the GND connector. This is not good in terms of electromagnetic ...


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The major concern with DMX specifically is the potential for a screwup somewhere in the rig to dump mains onto the DMX line, it shouldn't happen, but moving equipment, lots of temporary cable, hot lights... It does. Now contrary to others here, a correctly made DMX cable will generally not connect the connector shell to the screen, inferior from a RFI ...


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Using high power LED light bars to "blind" the crowd in a concert is not a harmless joke, it may be dangerous to the eyes. Carefully read the datasheets and application notes of high power LEDs. I developed an array of intense LEDs some years ago. When I looked into a LED for a short moment, I got a partially blind spot in my eye, no permanent damage, but ...


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Traditional DMX (not RDM) uses one master multiple slaves bus topology and is single direction. The Ethernet versions, 10base-2 and 10base-5, that use bus topology are obsolete. So Ethernet needs switches. DMX is simple. Practically any microcontroller with an UART interface can easily be made into a DMX receiver. With Ethernet, you probably want to use the ...


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This depends if you want interoperability with the equipment and wiring likely to be installed. Most theatres already have miles of suitable DMX cabling, plenty of ports and the distribution infrastructure to get the signals around. Many will also have a DMX capable lighting desk, even if it's very basic. DMX is so popular because it's basic and relies on ...


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You can do what you like; you could use the old Rank Strand analogue multiplex if you like (it's a joy to watch on an oscilloscope, for a start). The issue is whether you want your light units, whatever they are, to also be able to interface to DMX. If not, knock yourself out. DMX may be more robust than ethernet in an electrically noisy environment, though ...


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While it SHOULD work, you would be at the mercy of the DMX implementation on the receivers, and there is all sorts of weird out there. In practise you need to be very conservative in what you generate if you want random DMX kit from anything other then first tier vendors to work properly. Personally I would use a couple of the unused pairs in your Cat 5 ...


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You can't in general connect multiple drivers to a single LED, they are likely to damage each other. Why don't you replace it with four white LEDs, each connected to a single driver? That way it should be electrically good and you can adjust the brightness by an extra 6dB.


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