Newbie here. Working on a Halloween costume for my daughter and we have the need for some servos.
I have an Arduino Uno rev 3 and I would like to house it in a nice case that has ports for the barrel and the USB b connectors. The case will have two buttons for input to control the brightness of LED and also to move two servos in sync.
I plan to power the servos separately. The micro ones don’t take too much draw - maybe .25A but I might need larger ones. I have a 5V/3A power bank I plan to use. I cut a USB so one end will have leads going into the nice case and I will have two leads go the the arduino and two powering the servos. I know how I will do it and tested it. So I’ve tested this and it works.
Edit: just informed barrel connector must have 7-12V so changing my question to:
Can I intercept incoming power from USB b connector BEFORE it goes into the Uno to power servos independent of Uno.
BUT, if I want to use the case WITHOUT a cable hanging from it (either aesthetics or to avoid someone plugging into the barrel or just for my knowledge, I would like to be able to plug the power bank into the USB B connector without a pigtail usb cable. So for argument sake, let’s say I need to use the USB b connector.
QUESTIONS:
If I use the USB b connector with a power bank, is there a way to capture the full 5V/3A power from a set of pins on the board BEFORE the power regulator circuit regulates voltage or applies polarity protection etc that may limit the amps out. I thought I saw where the Vin is the regulated to 5V but the amperage is limited to 500mA or something like that. Can someone confirm? If Vin restricts amperage below my desired amount (I’m planning for larger servo let’s say I need 1.5A for the Servos). That means if Vin limits today .5 or 1amp it won’t be enough for the servos. Is this true about amperage being limited on Vin?
If it is true, are there any other pins that let me access the power banks full 5V/3A power? Can I instead solder leads to the USB b connectors pins in the underside of the boards?
Thanks
The voltage input to the barrel connector or Vin must be between 7V and 12V, so a 5V power bank will not work.
Your servos should be powered directly from the power bank and not through the Uno
I missed the 7-12V input. That means I would need to usb b connector. Same question though…
I’m not powering the servos from the Uno. Currently, I have a pigtail coming into the case and I have two wires going to Vin for the uno and two wires going to servo and have common ground to the uno but it requires a pigtail hanging out of the box to connect to the power bank . I’m asking if I could intercept the power from the barrel connector or USB b BEFORE it goes into the Uno for the same purpose - powering Servos directly - without adding a pigtail.
It's quite difficult to understand your question. If you have single power supply (powerbank), you can use two cables if it has two ports or you can buy split cable or build it by yourself. Since you have single psu, your GND is common already.
Draw a picture!
Yes. I already did this. I created a splitter cable going into the box.
What I’m asking is instead of creating my own cable, can I use the usb b port already in the board and intercept the incoming 2-3A before the Uno reduces amperage at Vin and 5V pins
Thanks. Now, once it gets to the uno board, it will drop amperage to the Vin and 5V pins below what I need for servos. Is there a way to intercept the power from the USB b pins BEFORE the power is regulated?
Use the 5V power bank for the servos, then a 9V to power the UNO, I almost always use a 9V for small projects like this.
INTERRUPT
Are you trying to split out the powerbank 5V to a USB plug and a 2 wire x plug for the servos? That sounds good until you get noise from the servos causing the UNO to reboot. But try it anyway, just be prepared with plan B, 2 independent PSUs.
Power from the USB port is not regulated, it goes directly to the 5V output pin NOT Vin
However you should NOT use either pin to power servos.
Your best solution is the one you have with the split cable.
Huh? I’m saying that the Vin (I believe) limits the amperage so I cannot use it to power servos. I want to intercept the higher amperage power from the power bank from the usb b connector somehow.
Ah ok. So I could get interference trying to run both. I’m already doing it in a test board. I made a pigtail leads by cutting a usb cable. Run the power to a breadboard at 5V/3A then power the Uno and servos from there. No issue so far but only micro servos.
But this still means that I need to add some extra port into the case for the servo power. It seems I can’t use the existing ports and steal the power huh?
This has to be carried around under a costume so I’m trying to keep it compact. If I wanted to use the pigtails and only one power source, is there a circuit to split and isolate power between Uno and Servos?
There are NO existing ports, USB is inout only, barrel jack is input only and none of the pins can help as they are limited to a few nilli amps but you need waaaaay more power than that.
I don't know of a single case of a motor being powered directly from the logic pins of any MPU or MCU.
What is common is a big power supply for some kind of motor (servos is still a motor) and then with adequate filtering for noise a tap to power the MPU or MCU