I used 6 rechargeable AA batteries (total 7.2V) to power my Arduino (UNO R3) Car's two DC Motors (using L293D IC as motor driver). I used separate 9V battery to power Arduino itself. But I want to share same 6 battery pack to power my Arduino via barrel jack. Please suggest me how can I do this? What precautions should I take? Like decoupling capacitors or any other?
Electrical – Share battery pack with Arduino and DC motors
arduinodcmotor
Related Solutions
I would guess you might have had a failure on one of power supply components. Here's the schematic for your board: http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf
Here are a few thoughts:
- What is the actual voltage on your 5V battery? If it's not fully charged, it may not have enough voltage to keep everything running.
- Check the voltage across fuse F1 as you plug in the battery... Perhaps the battery is allowing for a higher inrush current than the USB bus, causing this fuse to open? This doesn't seem likely as there's not that much capacitance on the board, but is easy to check.
- It's possible it's not a power supply problem at all... can you clarify what you mean by "it doesn't work"? Does the board appear to power? It could be that you're not properly grounding your serial connection to whatever you're communicating with, and having it plugged into your computer via USB is providing an alternate path for the serial ground and causing serial communications to work. Without more knowledge of what you're communicating with and how it's connected, however, this is nothing more than a wild-ass guess.
Your solution will work in principle.
The following will work for any generic uC (microcontroller).
You could automate it by providing a high side switch (MOSFET or bipolar) that was turned on with a momentary action push button, held on by the uC, and turned off by the uC when desired. There is then no prospect of hunting or hysteresis as the battery voltage rises when deloaded as when it's off it stays off until the user turns it on.
Size R2 to suit output current.
MOSFETS can be used for Q1 or Q2 with minor changes.
Switch Go! has to be held low until the uC takes over hold-on control.
Adding a capacitor across SW1 will allow circuit to remain on for a small period until the Arduino takes over.
simulate this circuit – Schematic created using CircuitLab
For extra points have a warning buzzer at a slightly higher voltage so you get a chance to take action before auto shutoff (hat tip to 46464).
The divider resistors should be as high as the ADC spec allows to minimise wasted current (only about 0.5 mA here but it all helps).
0.9V is well down the NimH discharge curve - especially if current is <= C/5, as is usually the case in this sort of application. I'd use closer to 1.0V/cell. Higher cutoff voltages will give substantially better cell cycle life with only a small decrease in available battery capacity.
Best Answer
It is possible to do what you are asking about, but there are some potential problems.
First, motors generate voltage spikes. You will want to prevent those from getting into your Arduino and possibly causing damage. Capacitors are a good start but you should put some additional protection on the power lines like a varistor or TVS to knock the voltage spikes down.
The second issue is the voltage selection. The Arduino runs on 5V. Your battery is 6V. Voltage regulators require something called “head room”. This is the minimum voltage above the regulator output voltage. Depending on the type of regulator, this might be .5V or so, on up to 1.5V. If the input voltage is not high enough, the regulator won’t work. A 6V battery does not give much head room for a 5V regulator.
A 6V motor will probably work pretty well down around 5V in many applications, as the battery becomes discharged. The Arduino will stop working well before the motor is the issue. You are likely to find that you don’t get very good battery life before the project stops working unless your 6V battery is very large and your motor does not draw much current.