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Topic: Making 120v Matrix ? (Read 4517 times) previous topic - next topic

blackrockcity

I have about 100 red 12" circular traffic led signs. I think they were used as railroad crossing warning signs. Each sign has about 200 LEDs and runs off of 120v using about 11watts. I would like to use a relay board and control these like a huge led matrix wall essentially using each relay per light as if it was an individual led in a matrix.. is this possible?

CrossRoads

Sure - with a relay you couldn' switch too fast tho.
120V AC?
You could make up your own shift register/relay board to run it.
Use 10 bits of shift register in X/Y configuration, use open collector parts like tpic6B595, both high allow the relay to turn on, either low would keep it off.

Let me think how to do that with diodes so the intersections are isolated (like a diode AND or OR gate) and not require  multiplexing... or just wire up 13 shift registers with SPI to drive them for fast control.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

winner10920

Im not sure of the actual speed of a relay but just an idea is you could probably use triacs to switch the supply to them, that would switch them at the frequency of the mains power, perhaps fast enough to matrix

Or since its leds it can probably be driven by dc at somepoint inside, if your lucky maybe 120dc would work
( time for 10x 12v baterys lol)
im sure the make a high voltage rated transistor or mosfet and since its only about 100ma they should be fine

blackrockcity


Sure - with a relay you couldn' switch too fast tho.
120V AC?
You could make up your own shift register/relay board to run it.



Let me think how to do that with diodes so the intersections are isolated (like a diode AND or OR gate) and not require  multiplexing... or just wire up 13 shift registers with SPI to drive them for fast control.


wow just realized how new i am to this. Not sure what a shift register board, ive found some relay board for arduino and other microcontrollers on ebay and was thinking of using that but curious if it would be fast enough.

"Use 10 bits of shift register in X/Y configuration, use open collector parts like tpic6B595, both high allow the relay to turn on, either low would keep it off." <-- not sure what the shift register or tpic6b595 do but does it allow the response time needed to allow the relay flashing required for matrix?

blackrockcity


Sure - with a relay you couldn' switch too fast tho.
120V AC?
You could make up your own shift register/relay board to run it.
Use 10 bits of shift register in X/Y configuration, use open collector parts like tpic6B595, both high allow the relay to turn on, either low would keep it off.

Let me think how to do that with diodes so the intersections are isolated (like a diode AND or OR gate) and not require  multiplexing... or just wire up 13 shift registers with SPI to drive them for fast control.


ok i think i see what your getting at with the tpic6B595, so use that chip with ShiftOut and connect relays? then the relays should be able to respond faster?

CrossRoads

#5
Sep 29, 2011, 07:58 am Last Edit: Sep 29, 2011, 08:29 am by CrossRoads Reason: 1
Yeah, I don't think that's gonna work now, relays are not gonna be happy for long being multiplexed. Better off with a bank of shift registers, transfer to each one with SPI and individual latch lines so not shifting data thru every part for any 1 light change. Each shift register output will control 8 relays for AC on/off to each light.

Update a group of 8:
digitalWrite(CS0, LOW ) ;
SPI.transfer(row0 ) ;
digitalWrite(CS1, HIGH ) ;

Or put in a for:next statement, update all whenever something changes, basically:

for (x = 0 to 12){
digitalWrite(CS
  • , LOW ) ;
    SPI.transfer(row
  • ) ;
    digitalWrite(CS
  • , HIGH ) ;
    next x ; }

    That will update fast!

    Make sure all parts have 100nF caps across their VCC/Gnd pins.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

dc42

#6
Sep 29, 2011, 01:28 pm Last Edit: Sep 29, 2011, 01:30 pm by dc42 Reason: 1
I think you need to take the sign apart and see how the LEDs are wired. You'll probably find that inside the sign, the 120vAC is converted to DC, and the LEDs may be arranged in strings of several in series. Each string might be driven from the DC through a series resistor, or from an inverter designed to regulate the current without the power loss of a series resistor.

If you want to control each led independently, it's probably best to remove the power supply provided and drive the LEDs from 5v using series resistors. Then you can use transistors to switch them, or drive them directly from suitable shift registers. This will be cheaper than using relays, more reliable, and much quieter.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

blackrockcity


Yeah, I don't think that's gonna work now, relays are not gonna be happy for long being multiplexed. Better off with a bank of shift registers, transfer to each one with SPI and individual latch lines so not shifting data thru every part for any 1 light change. Each shift register output will control 8 relays for AC on/off to each light.

Update a group of 8:
digitalWrite(CS0, LOW ) ;
SPI.transfer(row0 ) ;
digitalWrite(CS1, HIGH ) ;

Or put in a for:next statement, update all whenever something changes, basically:

for (x = 0 to 12){
digitalWrite(CS
  • , LOW ) ;
    SPI.transfer(row
  • ) ;
    digitalWrite(CS
  • , HIGH ) ;
    next x ; }

    That will update fast!

    Make sure all parts have 100nF caps across their VCC/Gnd pins.


I was thinking about using something like this off ebay for the relay http://www.ebay.com/itm/8-Channels-5V-Relay-Module-Arduino-ARM-PIC-AVR-DSP-/290610543299 and then with your suggestion a shift out board.. think thatll do?

blackrockcity


I think you need to take the sign apart and see how the LEDs are wired. You'll probably find that inside the sign, the 120vAC is converted to DC, and the LEDs may be arranged in strings of several in series. Each string might be driven from the DC through a series resistor, or from an inverter designed to regulate the current without the power loss of a series resistor.

If you want to control each led independently, it's probably best to remove the power supply provided and drive the LEDs from 5v using series resistors. Then you can use transistors to switch them, or drive them directly from suitable shift registers. This will be cheaper than using relays, more reliable, and much quieter.


This is a good idea, I havent been able to crack one open (they are waterproof and sealed to not be opened again). I would eventually like to control maybe not each LED (i have over 20k LEDs), but how they are wired in series inside the sign would be really nice to have control over. My plan was to have each 120v sign working as an individual LED.

CrossRoads

I can't open the e-bay link, I was thinking something like these
http://www.mpja.com/5VDC-DPDT-DIP-RELAY/productinfo/18474+RL/
You said 11W, so well under 1A current draw?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

blackrockcity


I can't open the e-bay link, I was thinking something like these
http://www.mpja.com/5VDC-DPDT-DIP-RELAY/productinfo/18474+RL/
You said 11W, so well under 1A current draw?


http://www.google.com/search?q=8-Channels-5V-Relay-Module-Arduino-ARM-PIC-AVR-DSP&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox

1A current what would i need for 100 that were daisy chained with the shiftouts?

winner10920

Its more like 100ma per light
11w / 120v = .91 amps

CrossRoads

Yes, 0.91 for each relay. I was thinking 120/11 was a lot less for some reason.

So you'd a 100A power supply, or several smaller ones. That current only goes thru the light & the relay tho, so you can have ten 10-amp supplies for example.
Since that current is being switched thru relays, they can be totally isolated from the arduino/relay coil power & ground.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

winner10920

Ooops, typo I just noticed I forgot a zero when I typed that
11/120=.091
so 100 lights would be 9.1 amps, big difference lol

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