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newbie: Simple microcontroller circuit gone bad

S

SEB

Jan 1, 1970
0
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.
 
J

John Popelish

Jan 1, 1970
0
SEB said:
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.

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).
 
C

CFoley1064

Jan 1, 1970
0
Subject: newbie: Simple microcontroller circuit gone bad
From: "SEB" [email protected]
Date: 12/11/2004 8:56 PM Central Standard Time
Message-id: <[email protected]>

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.

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
 
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