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Power Supply for line follower.

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Newbie level 5
Sep 5, 2006
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Hi all,
I'm making a Line follower robot , in which I've connected the outputs of the 2 IR sensors to 2 separate input channels of an AVR Tiny 13's ADC channels, the controller monitors the input, thereby controlling an L293D which in turn controls 2 motors. For power supply I'm using a 7805 to reduce the 9V input from a battery to 5V ,along with a heat sink).The motors are quite small and when i checked them ,they drew 60-65 mA each.

The problem is that the whole circuit is now drawing 620 mA(dont know where all the current is going),so i cant run it with a 9V battery.The robot is working perfectly fine when i use a constant voltage source using a adaptor.

So can anyone please tell how much current can a 9v battery supply at constant 9V for a considerable period of time and is there any other alternative portable power supply solution for this.

hoping for a quick reponse.


4 x AA NiMH batteries in series give you 4,8-5,2 V (depending on the state of discharge)
You can select between models with up to 3Ah (4,5 hours work of your robot)
The advantage is that you can use the battery block without 7805 regulator so you will not loose power for reduceing 9V to 5 V (40% of battery power goes for 7805 heating).
The size is about the same.
4 x AAA batteries are smaller, but available capacites are limited to 1Ah, may be 1,2 Ah.
If you have other devices in your robot , that needs for example 3,3 V supply
the inductance type switched mode supply is more efficent that linear stabilisators. (like 7805, LM317).
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