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Author Topic: 7219 Additional component requirements?  (Read 432 times)
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Hampshire
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So I got working ages ago some 7219s working on my breadboard on a matrix. very simple only required one passive and that was a resistor from 5v to pin 18 (sets the voltage for the leds) I chose 22k (Worked fine).
I want to externalise the matrix so I soldered on wires to the matrix to then a breadboard. I then use the 3 wires straight from the breadboard to the arduino. (And of course power and ground). When I do this I sometimes get a flicker. But nothing stays. I think this tells me that maybe the signals integrity or something is reducing over the wires(bare in mind there not long only 20 cm  project wire). I was wondering if anyone could think of any additional components to add to increase my luck? Its not my soldering as Its hard to get it wrong. (Just wires from matrix directly into the IC)

I hope there is something that can be done and if wire does affect it (hopefully not) I am using 7/0.2 Wire ( very nice wire smiley-grin)

Thank you for reading, ill look forward to see what i can do.
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TrevorB

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Add 2 caps on the Vcc pin - 0.1uF and something in the range of 1 to 10uF.

The resistor sets the current, not the voltage, thru the LEDs.
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Hampshire
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Brilliant! Sounds good smiley Ill will start the board again and see what the results are. Hopefully it'll work!
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TrevorB

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I tend to put a 10uF and 0.1uF across VCC GND close to the MAX7219 chips as per this image.
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Hampshire
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OK, Well I am working today at maplin (part time) so I mill need to pick up a few capacitors. Thank you for your suggestions. Hopefully Ill have it working tonight. smiley Knowing myself Its probably going to leave me with more problems! Thanks guys smiley Ill update you smiley-wink
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TrevorB

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Have got The components in, but has a busy night, will install tomorrow instead. I had a little research and now know what the smaller capacitor does within the circuit(hopefully). Does it help make the chip 'understand' or prevent it from getting the two frequencies etc. I guess from the several inputs? And possibly the PWM for the LEDs. OR is just for the data lanes
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