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Author Topic: Which is the most efficient battery for Arduino Uno?  (Read 2113 times)
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You can use sleep mode, and have the mcu wake up at regular intervals (so you can turn the servo) and also whenever the user presses a button (so that you can turn on the lcd and respond to user commands). However, if you use your Arduino Uno, then although you can put the atmega328p to sleep, the USB-to-serial converter will still be drawing power. That's why I said you need a standalone system.

You'll either need to power your mcu directly from a 3V to 5V battery (e.g. 3 x AA cells, if 4.5V signal is enough for your servos), or you'll need to use 6V or more battery and a micropower 5V regulator such as the MCP1702.

But won't the servo require continuous power and control pulses to hold any load they might it be trying to maintain? If so I don't think any 'sleep' mode would work well?

Lefty
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You can use sleep mode, and have the mcu wake up at regular intervals (so you can turn the servo) and also whenever the user presses a button (so that you can turn on the lcd and respond to user commands). However, if you use your Arduino Uno, then although you can put the atmega328p to sleep, the USB-to-serial converter will still be drawing power. That's why I said you need a standalone system.

You'll either need to power your mcu directly from a 3V to 5V battery (e.g. 3 x AA cells, if 4.5V signal is enough for your servos), or you'll need to use 6V or more battery and a micropower 5V regulator such as the MCP1702.

Hmmm.. I guess I'll just have to live with the 9V battery for now. Cos I need to present my project in school soon and I wont have time to come up with the standalone system so soon..

So comes another qn: is a 9V battery better or a 3 AA battery connected directly to the 5V pin of arduino better?
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But won't the servo require continuous power and control pulses to hold any load they might it be trying to maintain? If so I don't think any 'sleep' mode would work well?

I thought servos only move when you send them pulses?
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So comes another qn: is a 9V battery better or a 3 AA battery connected directly to the 5V pin of arduino better?

3 x AA will last a lot longer. But check that your LCD works OK on 4.5V.
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But won't the servo require continuous power and control pulses to hold any load they might it be trying to maintain? If so I don't think any 'sleep' mode would work well?

I thought servos only move when you send them pulses?

Lack of servo pulses but with power still applied to a servo is simply a undefined state for any servo, they just are not designed to perform any specific action in that state, it may move un-commanded or not move. They are designed under the assumption that if they are powered up there will be continuous position pulses being sent, even if to just maintain the present position.

  Also without servo power all 'holding torque' is lost and depending on external load on the servo and the friction value of the servo's gear train the servo can lose position as the external load forces movement.

Lefty
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So comes another qn: is a 9V battery better or a 3 AA battery connected directly to the 5V pin of arduino better?

3 x AA will last a lot longer. But check that your LCD works OK on 4.5V.

Sounds good. So for a current drawing abt 50mah  from the arduino and the LCD, how long more would the 3 x AA battery power last as compared to the 9V battery?

How much mAh rating does 1 AA alkaline battery usually have? Tried searching online but the values are ranging from abt 700mAh to as much as 2000mAh..

And would it be better to use rechargeable batteries or normal ones?

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http://data.energizer.com/ will give you typical capacities for alkaline batteries and the lithium versions of standard batteries. If you use rechargables, bear in mind that NiMH cells are about 1.2V not 1.5V, so you probably want to use 4 of them instead of 3.
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http://data.energizer.com/ will give you typical capacities for alkaline batteries and the lithium versions of standard batteries. If you use rechargables, bear in mind that NiMH cells are about 1.2V not 1.5V, so you probably want to use 4 of them instead of 3.

So am I right to say this:

Say I am using 4 x 1.2 V AA NiMH battery (2000mAh each). So total is 8000mAh and hence the battery would last for 8000/50 = 160 hrs which is slightly more than 6 days?
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No, the batteries are in series, so the capacity will be 2000mAh.
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No, the batteries are in series, so the capacity will be 2000mAh.

Oh darn. But normal alkaline AA batteries has abt 2500mah, compared to 9V batteries that has only abt 600mah..

So I'll just go with 3 AA alkaline batteries, as it would at least be able to work for 2 days..

Just another doubt to clarify: the 4.5V supply wire has to go to the 5V pin or the Vin Pin of the arduino?
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Oh no! Just checked the datasheet for my LCD display and it needs 5V supply.

So can I use 4 AA battery and connect it to the power socket in the arduino? WIll it loss too much power due to the 5V regulator heat dissipated?
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