Max 7219 capacitors
RD
Posts: 8
Hello,
Could someone tell me where to put capacitors in my
max 7219 and LED matrix circuit?
I have been experimenting with the circuit in NV70,
and from the max 7219 datasheet, I could only find
one capacitor, on pin 19 of the max7219.
So I guess this is an experience thing.· And I was hoping for
someone to pass along some theory, and practice.
Thanks.
I'll need to know the values and whether ceramic or electro,
thanks.
·
Could someone tell me where to put capacitors in my
max 7219 and LED matrix circuit?
I have been experimenting with the circuit in NV70,
and from the max 7219 datasheet, I could only find
one capacitor, on pin 19 of the max7219.
So I guess this is an experience thing.· And I was hoping for
someone to pass along some theory, and practice.
Thanks.
I'll need to know the values and whether ceramic or electro,
thanks.
·
Comments
Not a lot of interest.
I have placed two sets of holes for a ceramic and an electrolytic cap on pin 19 to ground.· I guess if I don't need these I can leave them out and no harm.· I'm guessing that these capacitors act like shock absorbers to take in charge and release charge as the current fluctuates.· Whatever charge is anyway.
The real problem with my version 1 pcb was power.· I made a pcb to accept my stamp, and two LED matrixes and two max7219's using one 7805 voltage regulator.· Boy did that thing get hot!!!· Especially when I daisy chained the first board with a second and then a third.(6 matrices and 7219's)
It got so hot that things started blinking and I think I fried some 7219's.· After the fry and blink episode I took it apart and returned to a single board with two matrices and worked on programming instead.
Version 2.0 now has a voltage regulator, 7805 on each board, and the capacitors, and I intend to power each 7805 with power from my source transformer before any of the 7805's.· Hopefully this will put all of the 'demand' only on the transformer.· And I'm 'upgrading' to a 5vdc, 4A transformer, where I was using a 12vdc, 1.5A transformer.· Hope this make the wingless charge angels happy.· I'll let you know.
I think the problem is that it’s not clear what you needed/wanted. The only capacitor typically used in the designs with a MAX7219 would be a .1uF bypass capacitor located across the power pins as close to the IC as possible. No other capacitors are needed. I have several designs which employ these chips and none have had any issues with the power system, displays or the BASIC Stamp interface. Next week I will try to get some examples of using this device. Take care.
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Chris Savage
Parallax Tech Support