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Question about NSI dimmer pack upgrade

Discussion in 'Lighting and Electrics' started by JohnA, Dec 5, 2008.

  1. JohnA

    JohnA Active Member

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    Greetings to all,

    I am looking to upgrade several NSI DDS 6000 packs from microplex to DMX protocol. I know this has been covered before, but I could not find a direct answer in my forum search. So, if anyone has a link, feel free to provide it.
    I have a call in to NSI tech support & am awaiting a reply--but have tentatively been told "you can't just put an rs485 chip in there". I am finding that a bit hard to believe, since I know the chip is not an EEPROM.

    BTW-I would appreciate a straight forward answer, avoiding (-) comments or opinions on the NSI line.

    Thanks for your time--John A
     
  2. church

    church Active Member

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    All an RS485 chip does - depending on which chip is: is transmit, receive or both transmit and receive RS485 signals. The problem is those signals have to be in the 16 bit dmx format and you have to have an address decoder circuit to recognise which group of commands are for the dimmer unit and then convert the commands to the format required by the dimmer.
     
  3. JD

    JD Well-Known Member

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    Much of the NSI line has dual compatibility, but certainly not all. Microplex is its own format and is different than DMX. You may have to go to Doug’s site and get a translator.
     
  4. JohnA

    JohnA Active Member

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    Thanks for your replies. Per NSI, the DDS line is DMX ready. All I need to do is get an RS 485 chip & plug in & attach the leads to the dedicated bus located behind the DMX socket.
     
  5. dramatech

    dramatech Well-Known Member

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    The chip you need is a 75176. It may have some letters in front of it depending on who manufactured it. It will be an 8 pin DIP, that is four pins on each side. There will be a little dot over pin one or a a little dent in the end where pin one is. Most circuit boards will have a drawing of the chip with the dip printed on the board. Make sure that you line up the dent on the chip with the dent indicated on the Printed circuit board. On the side of the board will likely be three pins that will receive a header socket. The pins will probably be labeled 1,2,3. It is pretty straight forward pin 1 on board goes to pin 1 on an XLR socket and the same with the other two pins. As 5 pin XLRs are the standard for DMX, although many lesser expensive devices use 3 pin, you should use the five pin as the microplex on the dimmer pack will have a 3 pin and you don't want to confuse the two. Five pin XLR connectors are pretty expensive from Switchcraft and Neutrix, but Pomona XLRs are much less expensive and of similar quality. The chip and connector are available from mouser.com. There is no minimum order, but UPS ground will be as much as the components. You may want to order mic connectors, 120 ohm resistors and additional 5 pin DMX to make terminators or whatever in order to justify the shipping charge. And by the way the chassis mount connector for DMX in, on the dimmer pack should be a male connector.
     
  6. jreckart

    jreckart Member

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    So, has anyone just added the chip and header and it worked?
     
  7. mrb

    mrb Active Member

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    ive done it to several consoles, and i think I did a dimmer but it was so long ago im not sure. I seem to remember the chip for the console being a max485, i dont know if the pinout is the same as a 75176 or not.
     
  8. church

    church Active Member

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    the pin out is the same. I use DigChip IC database for quick access to datasheets.
     
  9. BillESC

    BillESC Well-Known Member Premium Member

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    A5512-000 is the part number for the DMX conversion kit. MAP price for it is $ 103.95
     
  10. JohnA

    JohnA Active Member

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    My NSI DDS6000's took the MAX485 chip with no problem. Total cost--a couple of bucks.
     
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  11. liu

    liu Member

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    I know it's been awhile since this post but I have a question. Which 75176 chip is it on Mouser.com? It looks like there are several different ones. I just dont want to order the wrong ones. Thanks.
     
  12. liu

    liu Member

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    What is the diference between the 75176 chip and the max485 chip that others are refering to?
     
  13. dramatech

    dramatech Well-Known Member

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    There are a number of communicaton transceiver chips that are used for the DMX protocal. DMX is basically a command set that uses the RS485 standard. When dealing with the transmission and receiving of DMX signals, the chips or ICs should be RS485 compatible. I have found three different families of ICs that qualify.
    I am not book or school educated on the subject, but while rebuilding Wybron scrollers and power supplies, I discovered that there were more than just the 75176 ICs used in DMX signals. Upon searching suppliers for the 485 ICs that Wybron uses, I discovered that there is a third family of ICs, that falls between the 485s and 75176s in price. I believe, but I am not sure that Digikey carries all three. Mouser only carries the 75176 and 485 lines. When in question, I checked the data sheets on all three lines, and found the pin assignments the same, and most of the electrical specifications to be the same. I have used 75176 ICs to replace all of the other more expensive RS485 ICs with no problem.
    The important thing to observe when purchasing from Mouser, is that the ICs have through hole pins and are not surface mount. Because almost all of the 75176 ICs listed at Mouser are of the same manufacture, but different prices, it can be confusing as which ones to purchase. I usually purchase the ones that are just one down from the most expensive, and if I am purchasing just a few I will purchase the 485 ICs.
    Having now said that I would expect at least 6 people to respond that I should use some sort of more scientific method of choice in the purchase of these ICs. I have yet to have a problem with any that I have used.
    In helping out 5 or 6 theatres in our area, I have gone through quite a few 75176 ICs. They seem to be the item that gets sacrificed during a lightning storm to save the rest of the circuitry. I just got through repairing 12 Wybron Forerunner scrollers, where everyone was just the Communication IC. One of the units had the chip and socket completely burned off the board. They all went out during a show and during a storm. The console also lost two of the three ouputs in that storm and replacing the ICs was all that was required for the repair.
    The theatre that I repaired the console and scrollers repaid me by buying me 75 of these ICs. I am retired and I don't charge them anything for the repairs, but they purchased these ICs as a jesture of thanks. I think that I am ready to handle the community of theatres for a while.
     
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