Hi! I found a tutorial to connect the PWM driver TLC5940 to Aduino and the following diagram was included:
Which role have the capacitors?
I suppose they are uncoupling capacitors but, Why 0.1 and 4.7 uF and the last one electrolytic?
What capacitors should I use?
Regards and thanks!!
Decoupling capacitors are to prevent switching noise from getting into the electronics, or to prevent oscillation.
You probably don't need the 4.7uf cap, but check the manufacture's datasheet to see if they recommend it. Electrolytic capacitors don't "act like" capacitors at very-high frequencies, so depending on the application it's not unusual to put a smaller ceramic capacitor in parallel with an electrolytic.
P.S.
The TLC5940 datasheet says:
The Vcc power supply voltage should be decoupled by placing a 0.1uF ceramic capacitor close to Vcc pin and GND plane. Depending on panel size, several electrolytic capacitors must be placed on board equally distributed to get a well regulated LED supply voltage (VLED).
Whoever wrote that tutorial failed you. The TLC5940 has to have a decoupling capacitor across VCC & GND as close as possible to the chip.
I have first hand experience that the TLC5940 may not function correctly without it.
DVDdoug:
Decoupling capacitors are to prevent switching noise from getting into the electronics, or to prevent oscillation.You probably don't need the 4.7uf cap, but check the manufacture's datasheet to see if they recommend it. Electrolytic capacitors don't "act like" capacitors at very-high frequencies, so depending on the application it's not unusual to put a smaller ceramic capacitor in parallel with an electrolytic.
P.S.
The TLC5940 datasheet says:
Thanks so much!!
Then, the 4.7uF electrolytic capacitor can be useful for my application, right?
Regards and thanks!!
Then, the capacitors are well connected in the above diagram?
Regards and thanks!!
Do you see a connection between a capacitor and VCC?
Then, the capacitors are well connected in the above diagram?
That will be a no then.
C2 and C1 are connected to 5v, vcc is also connected to 5v. Electrically they are connected in the diagram (assuming its not two separate 5v sources). Physically the decoupling should be as close as possible to vcc pin.
They put the capacitors in a very odd spot in the schematic.
alka:
C2 and C1 are connected to 5v, vcc is also connected to 5v. Electrically they are connected in the diagram (assuming its not two separate 5v sources). Physically the decoupling should be as close as possible to vcc pin.
They put the capacitors in a very odd spot in the schematic.
That's not particularly odd.
I've seen schematics where all the decoupling caps were off in the corner, so you see a big pile of 0.1uf caps in the corner of the schematic. I mean, not that I advocate that practice, but it's not uncommon :-/
alka:
(assuming its not two separate 5v sources)
What's that saying about "assume"?
LOL, ok you are right, it is unlikely they are two separate 5 v sources though.
They would have different names if they were different signals or supply rails.
Yes, it is very common in schematics to have all the bypass capacitors off in a corner of the sheet. Relying on the knowledge of whomever is laying out the board to put them in the correct place.
Not a safe assumption with hobbyists.