Hello, super newbie here, hoping to be posting this in the right section.
I'm learning and hoarding informations to build a personal project, an almost full digital Airsoft rifle. I'm thinking about using an Arduino Nano (because of the dimensions) to manage the control of the rifle. When the trigger is pulled, the Arduino should close a low power circuit that drives a MOSFET close and lets the battery power the motor.
Given that the rifle has to be powered by a battery (8,4 or 9,6 v NiMH or 7,4 or 11.1 v LiPo, the "worst" case being the 11.1v), I would like to use the same battery to supply power to the Arduino too but I'm worried about blowing it up. I read many discordant opinion so I would like some clarity.
How can I safely power the Arduino with this kind of battery?
Is there difference between powering it through the usb or the Vin/Gnd pins?
The best way, in my experience, is to apply the battery power to a DC-DC converter to convert the battery power to 5V that you apply to the 5V pin. Powering through the Vin pin or power jack means that 5V is supplied by the weak onboard regulator.
So there is another pin that can power the Arduino beside the Vin?
Can you please link me or tell me one DC DC converter?
And sorry to ask this question but does the Arduino need only a single pin (a positive one?) to be powered?
EDIT: please keep in mind that the dimensions are important for me. I know that a big regulator will probably work better but I would like it to approximately be as little as the Arduino
Pololu has a selection of step down (buck) converters with 5V outputs. Similar units are available from eBay and other vendors.
You can feed power into to 5V pin (and ground). The voltage must be a well regulated 5V. When you do you bypass the weak onboard 5V regulator.
The regulators that I linked to are pretty small. Less than 1" (25mm) square.
You may be able to get away with powering through the Vin pin if you have little else connected to the 5V regulator. You must take care to not overload the regulator. Keep the power dissipated by the regulator under 1 Watt.
Thank you. I still have some questions though since I'm really ignorant (reading through some documentation and tutorial right now but I can't find answers). If I supply power to the Arduino through the Vin or the +5V, do I have to connect a positive cable to one of them AND a negative cable to the Ground? If yes, the negative cable should go from the Ground to the negative pole of the battery?
Also, if I decide to delete the 11.1v battery and settle for a 9.6v NiMH or a 7.4 LiPo, can I use the Vin pin without blowing up the Arduino?
Here is how the battery would connect using a buck converter voltage regulator or directly to the Vin and ground.
Also, if I decide to delete the 11.1v battery and settle for a 9.6v NiMH or a 7.4 LiPo, can I use the Vin pin without blowing up the Arduino?
You probably will not blow up the Arduino. If you pull more current from the onboard 5V regulator than it can supply without overheating, it will shut down.
If you want to connect the battery (11.1V, 9.6V or 7.4V) to Vin you can. Doing so means that anything connected to the 5V rail will be supplied by the onboard regulator. Be aware that dissipating more than 1 Watt by the onboard 5V regulator can cause the regulator to shut down. So with a 11.1V battery connected to Vin the max current that can be safely supplied by the 5V regulator is about 110mA.
Thank you very much!
groundFungus:
If you want to connect the battery (11.1V, 9.6V or 7.4V) to Vin you can. Doing so means that anything connected to the 5V rail will be supplied by the onboard regulator. Be aware that dissipating more than 1 Watt by the onboard 5V regulator can cause the regulator to shut down.
If I'm not wrong, when I connect a power supply to the Vin, the 5V pin will not behave like a Power Input and instead it will behave like a Power Output, so a power supply for other things connected to it, right?
groundFungus:
Be aware that dissipating more than 1 Watt by the onboard 5V regulator can cause the regulator to shut down. So with a 11.1V battery connected to Vin the max current that can be safely supplied by the 5V regulator is about 110mA.
I just have to digitally connect and disconnect two pins, the two that once connected togheter will close the MOSFET, if I'm not wrong I don't think it to be power hungry, right?
it will behave like a Power Output, so a power supply for other things connected to it, right?
Yes, that is right.
if I'm not wrong I don't think it to be power hungry, right?
I don't know, but probably not be power hungry. I can't be sure without seeing a complete schematic. Verbal circuit descriptions are never as good as a good schematic.
Two pins that are connected together sounds like a really bad idea that will damage the Arduino.
But since you have not show us a schematic or any code you might mean something quite different from what it sounds like.
Steve
slipstick:
But since you have not show us a schematic or any code you might mean something quite different from what it sounds like.
Sorry, as I said I'm really ignorant but I want to learn. I don't have any code yet as I have to still buy everything and start playing with it, and I don't know how to write any schematic so I came up with these, hoping it is readable and easy to understand
EDIT: I found this ESP8266. It seems to be an Arduino like platform. As based on what I have found online about it, it seems like a cheaper, better performing platform and I'm thinking about buying this
EDIT 2: I'm watching some instructional videos, seems like that to read a button (the two microswitches) I have to connect them between a Digital Pin set in Pullup mode and Ground
Update: I learnt that I can set up a button (a switch) by connecting it between a digital pin set to Input Pullup and Ground. This way I can control when the button is pressed so I can use it correctly as a trigger.
I also learnt that I can drive a MOSFET by applying 5v between the Source (grounded) and the Gate pins, but there are some problems:
- The videos talked about some kind of mosfets, while I have a commercial airsoft mosfet (Gate nano ASR) so I don't know how to detect the pins. There are two little pins on this mosfet that when connected togheter they open the mosfet that lets the current flow, but I don't know which of them is which.
- I read with a multimeter that between these two pins flows a current of the same voltage as the power supply (a battery between 7.4 and 11.1v) so I'm afraid that connecting them to the Arduino will fry the pins. Maybe I can ground a pin on the arduino (or the switch regulator that powers it) and connect the other with a digital pin?