newbie: Simple microcontroller circuit gone bad
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Posted by SEB on December 12, 2004, 5:56 am
Please log in for more thread options First post and just beginning in microcontrollers and electronics, so please excuse the dumb questions. I have built a circuit with an Atmel 2051 that simply makes 4 leds flash quickly (about 400 hz), using the standard circuit set up for the 2051. It works fine but when I run it off of two 3volt watch batteries, they are dead after about 1 minute. My understanding is that this circuit should run for many hours with these batteries. I've been over the circuit lots of times looking for short circuits, but can't find any. a) is this normal behaviour or do I need to use some low power circuitry magic? b) where could I find examples if I need a different low-power schematic? Can anybody point me in the right direction? Thank you. -- Sean | |||||||||||||
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Posted by John Popelish on December 12, 2004, 1:47 am
Please log in for more thread options Watch batteries don't have much capacity to drive an LED, let alone 4 of them. How much current are you sending through each LED? First change would be to go to very high efficiency LEDs and drive them with low current ( a milliamp or 2). -- John Popelish | |||||||||||||
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Posted by CFoley1064 on December 12, 2004, 7:29 am
Please log in for more thread options >Subject: newbie: Simple microcontroller circuit gone bad
>From: "SEB" sean_public@burnettconsulting.ca >Date: 12/11/2004 8:56 PM Central Standard Time > >Hi, > >First post and just beginning in microcontrollers and electronics, so please >excuse the dumb questions. I have built a circuit with an Atmel 2051 that >simply makes 4 leds flash quickly (about 400 hz), using the standard circuit >set up for the 2051. It works fine but when I run it off of two 3volt watch >batteries, they are dead after about 1 minute. My understanding is that >this circuit should run for many hours with these batteries. > >I've been over the circuit lots of times looking for short circuits, but >can't find any. > >a) is this normal behaviour or do I need to use some low power circuitry >magic? >b) where could I find examples if I need a different low-power schematic? > >Can anybody point me in the right direction? > >Thank you. > >-- >Sean Hi, Sean. Get 4 "AAA" batteries and a battery holder to give your 6V. Watch batteries aren't made for that kind of current draw. Even if your LEDs are flashing sequentially, you're probably drawing at least 10mA, which is at least 100 times the recommended maximum current for a watch battery. Even getting high intensity LEDs and running them at a couple of mA won't be good enough, and watch batteries are pretty expensive. http://www.radioshack.ca/estore/default.aspx?language=en-CA BATTERY HOLDER FOR 4 AAA CELLS Radio Shack P/N 270-413 $1.99 These should last for a day or two, at least. Good luck Chris | |||||||||||||
> Hi,
>
> First post and just beginning in microcontrollers and electronics, so please
> excuse the dumb questions. I have built a circuit with an Atmel 2051 that
> simply makes 4 leds flash quickly (about 400 hz), using the standard circuit
> set up for the 2051. It works fine but when I run it off of two 3volt watch
> batteries, they are dead after about 1 minute. My understanding is that
> this circuit should run for many hours with these batteries.
>
> I've been over the circuit lots of times looking for short circuits, but
> can't find any.
>
> a) is this normal behaviour or do I need to use some low power circuitry
> magic?
> b) where could I find examples if I need a different low-power schematic?
>
> Can anybody point me in the right direction?
>
> Thank you.
>
> --
> Sean