| Author |
Message |
Jim Dye
Guest
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 Posted:
Wed Nov 16, 2005 9:13 am Post subject:
555 Circuit Problem |
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I am trying out my first electronics project, a LED flasher that looks like
http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm (The one with
the 9V battery shown)
I have found numerous examples of the same circuit around the net...but
this one looks the clearest.
I have C as 100uF, R1 as 1K and R2 as 22K. Using the calculator, that
should have the LED flashing on and off for about 1.5 seconds each state.
The LED is set to draw 10mA on 9V
When I turn on the juice (9v --- and the reason I am writing)...the LED
goes flashes as expected BUT
1. It is very dim
2. The 555 is smoking and melting the breadboard.
I have tried several combinations using various intermediate steps for
wiring the same result.
Maybe someone with more experience could suggest something to look for.
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Bart
Guest
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| Posted:
Wed Nov 16, 2005 9:35 am Post subject:
Re: 555 Circuit Problem |
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"Jim Dye" <dummy@dummy.com> wrote in message
news:Jtxef.2426$Rb.2288@trndny04...
| Quote: | I am trying out my first electronics project, a LED flasher that looks
like
http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm (The one with
the 9V battery shown)
I have found numerous examples of the same circuit around the net...but
this one looks the clearest.
I have C as 100uF, R1 as 1K and R2 as 22K. Using the calculator, that
should have the LED flashing on and off for about 1.5 seconds each state.
The LED is set to draw 10mA on 9V
When I turn on the juice (9v --- and the reason I am writing)...the LED
goes flashes as expected BUT
1. It is very dim
2. The 555 is smoking and melting the breadboard.
I have tried several combinations using various intermediate steps for
wiring the same result.
Maybe someone with more experience could suggest something to look for.
|
I only mention this as you say its your very first electronics project.
On the breadboard, the 555 chip must be placed strategically straddling
the divider section so that there is no conductivity from any pin to any
other pin through the breadboard. Also, lookup the datasheet for your
555 chip to make sure its one that is OK with 9 volts.
HTH
Bart |
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Lord Garth
Guest
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| Posted:
Wed Nov 16, 2005 9:35 am Post subject:
Re: 555 Circuit Problem |
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"Jim Dye" <dummy@dummy.com> wrote in message
news:Jtxef.2426$Rb.2288@trndny04...
| Quote: | I am trying out my first electronics project, a LED flasher that looks
like
http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm (The one with
the 9V battery shown)
I have found numerous examples of the same circuit around the net...but
this one looks the clearest.
I have C as 100uF, R1 as 1K and R2 as 22K. Using the calculator, that
should have the LED flashing on and off for about 1.5 seconds each state.
The LED is set to draw 10mA on 9V
When I turn on the juice (9v --- and the reason I am writing)...the LED
goes flashes as expected BUT
1. It is very dim
2. The 555 is smoking and melting the breadboard.
I have tried several combinations using various intermediate steps for
wiring the same result.
Maybe someone with more experience could suggest something to look for.
|
Despite the flash, something is very wrong with your parts and / or your
wiring.
Please check the orientation of the 555 WRT pin 1, it is the pin to the left
of the
notch when viewed from above.
Did you use a fresh 555?
Did you verify the power supply is properly connected to the 555?
Is the LED shorted or connected in reverse?
Your LED needs 10ma @ 9v or 900 ohms, use 820 ohms
The resistor should be gray red brown.
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tom@waymouth.co.nz
Guest
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| Posted:
Wed Nov 16, 2005 9:35 am Post subject:
Re: 555 Circuit Problem |
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I think maybe you should try something easier. Have a look at this led
flasher it only uses a few parts and isn't that fussy about things like
voltage and component values.
http://xedox.de/blinker.htm
When I first tried to build an led flasher mine started smoking as well
:) |
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John Fields
Guest
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| Posted:
Wed Nov 16, 2005 5:35 pm Post subject:
Re: 555 Circuit Problem |
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On Wed, 16 Nov 2005 03:13:45 GMT, Jim Dye <dummy@dummy.com> wrote:
| Quote: | I am trying out my first electronics project, a LED flasher that looks like
http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm (The one with
the 9V battery shown)
I have found numerous examples of the same circuit around the net...but
this one looks the clearest.
I have C as 100uF, R1 as 1K and R2 as 22K. Using the calculator, that
should have the LED flashing on and off for about 1.5 seconds each state.
The LED is set to draw 10mA on 9V
When I turn on the juice (9v --- and the reason I am writing)...the LED
goes flashes as expected BUT
1. It is very dim
2. The 555 is smoking and melting the breadboard.
I have tried several combinations using various intermediate steps for
wiring the same result.
Maybe someone with more experience could suggest something to look for.
|
---
Sounds like you might have the wiring to pins 7 and 8 reversed.
--
John Fields
Professional Circuit Designer |
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