Hello,
i have a rp pca9685 hat and need an assistance to determine if needed another capacitor to run in total 400ma? note that i dont need more than 400ma max (only for signals). if so, a 33uF in addition to the existing 10uF is enough? and also to add a 0.1uf next to the 10uf?
Thank you in Advance
add cap to rp hat
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adafruit_support_mike
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Re: add cap to rp hat
If you're using a Servo Hat, you won't be able to get 400mA from the PWM signals.
The signals go through 220-Ohm resistors before they reach the pins at the edge of the PCB. The most current you can get from any pin is about 25mA.
If you're using 25mA on each of 8 channels for a total of 400mA, you may need some additional capacitance to keep the supply voltage stable.
The exact amount of debounce capacitance you need depends on the strength of your power supply, but 1uF per milliamp of expected current tends to be a good starting point. That will limit voltage spikes to a slew rate of 1V/ms, and most voltage regulators can cope from there.
In the end, it comes down to testing the circut and deciding how much voltage ripple is acceptable.
The signals go through 220-Ohm resistors before they reach the pins at the edge of the PCB. The most current you can get from any pin is about 25mA.
If you're using 25mA on each of 8 channels for a total of 400mA, you may need some additional capacitance to keep the supply voltage stable.
The exact amount of debounce capacitance you need depends on the strength of your power supply, but 1uF per milliamp of expected current tends to be a good starting point. That will limit voltage spikes to a slew rate of 1V/ms, and most voltage regulators can cope from there.
In the end, it comes down to testing the circut and deciding how much voltage ripple is acceptable.
Please be positive and constructive with your questions and comments.