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Here's a start;I now find there are various types of 555 chip eg....NE555 or NE555D SMD
Could anyone advise please.
I now find there are various types of 555 chip eg....NE555 or NE555D SMD
Could anyone advise please.
Here's a start;
DESCRIPTION TEMP RANGE ORDER CODE
8Pin Plastic Small Outline (SO) Package 0 to +70 °C NE555D
8Pin Plastic Dual InLine Package (DIP) 0 to +70 °C NE555N
8Pin Plastic Small Outline (SO) Package -40 °C to +85 °C SA555D
8Pin Plastic Dual InLine Package (DIP) -40 °C to +85 °C SA555N
8Pin Plastic Dual InLine Package (DIP) -55 °C to +125 °C SE555CN
8Pin Plastic Dual InLine Package (DIP) -55 °C to +125 °C SE555N
Get the data sheets and READ THEM! All the info you need is out
there, you've just gotta look for it.
google "555 timer types" and get this among many others;
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
niftydog@hotmail.com (Steve) wrote in message
news:<e28c5b43.0312181420.e828a8f@posting.google.com>...
I now find there are various types of 555 chip eg....NE555 or NE555D
SMD
Could anyone advise please.
Here's a start;
DESCRIPTION TEMP RANGE ORDER CODE
8Pin Plastic Small Outline (SO) Package 0 to +70 °C NE555D
8Pin Plastic Dual InLine Package (DIP) 0 to +70 °C NE555N
8Pin Plastic Small Outline (SO) Package -40 °C to +85 °C SA555D
8Pin Plastic Dual InLine Package (DIP) -40 °C to +85 °C SA555N
8Pin Plastic Dual InLine Package (DIP) -55 °C to +125 °C SE555CN
8Pin Plastic Dual InLine Package (DIP) -55 °C to +125 °C SE555N
Get the data sheets and READ THEM! All the info you need is out
there, you've just gotta look for it.
google "555 timer types" and get this among many others;
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
Thanks for the info & the site suggestion.
Smokeyone
to e-mail me, delete mail from address
For a 2 second astable, which is what I understand the OP wants, I'dThe 555 isn't going to be your best bet if you need anything close to precise
timing because the timing will drift based on both tolerance of the RC
components and the temperature. Also it isn't easy to get a 50 percent
duty cycle with the 555.
If this isn't battery powered, one of the most reliable source of time is
the power cycle from the wall. A center tapped transformer, along with a
single current limiting resistor and a zener diode, is all that's required
to get near rock solid 60 Hz pulses that you can divide/count down to your
heart's content. The transformer also will provide power to your project
with a bridge rectifier, voltage regulator, and an additional couple of
caps.
I use the above setup to drive any precise/long term timing PIC projects I
put together. Works like a champ.
This howstuffworks.com page describes the exact setup I'm talking about:
http://home.howstuffworks.com/digital-clock4.htm
Of course I believe the rest of the circuit past the power supply/60 Hz
generator falls down because it's a perfect application for a microcontroller.
Using discrete TTL, while useful as a learning exercise, is impractical for
real implementations. However if you're going discrete, pay attention to the
divide by 6 and divide by 10 on the subsequent pages.
Howstuffworks also talks about how to build a digital clock with a basic stamp.
They point out that the setup will cost $100. Insane. Fortunately you can
skip the stamp and program to an inexpensive bare microcontroller. Presuming
you're only wanting the same 1 Hz output as the 555, a 16F628 can be had
for less than $3, or on sample from Microchip.
BAJ
As I pointed out above it depends on the precision. A 555 is fine for 2 Hzbyron@cc.gatech.edu (Byron A Jeff) wrote:
The 555 isn't going to be your best bet if you need anything close to precise
timing because the timing will drift based on both tolerance of the RC
components and the temperature. Also it isn't easy to get a 50 percent
duty cycle with the 555.
If this isn't battery powered, one of the most reliable source of time is
the power cycle from the wall.
[ Snipped ]
For a 2 second astable, which is what I understand the OP wants, I'd
have thought a 555 was the obvious solution. Or half a 4001 or 4011.
Your own table points out that it isn't exactly 2 Hz. It'll be inaccurateA suitable circuit I posted here 3 months ago for a similar
requirement is shown at
http://www.terrypin.dial.pipex.com/Images/555Astable2s.gif
Thanks everyone for the replies. It certaintly will give me enoughIn article <7ec6uvkn4kepem4uloklq31o78uo2v16vl@4ax.com>,
Terry Pinnell <terrypinDELETE@dial.pipexTHIS.com> wrote:
byron@cc.gatech.edu (Byron A Jeff) wrote:
The 555 isn't going to be your best bet if you need anything close to precise
timing because the timing will drift based on both tolerance of the RC
components and the temperature. Also it isn't easy to get a 50 percent
duty cycle with the 555.
If this isn't battery powered, one of the most reliable source of time is
the power cycle from the wall.
[ Snipped ]
For a 2 second astable, which is what I understand the OP wants, I'd
have thought a 555 was the obvious solution. Or half a 4001 or 4011.
As I pointed out above it depends on the precision. A 555 is fine for 2 Hz
+/- 10 percent. But if it needs to be spot on, it'll fail miserably.
A suitable circuit I posted here 3 months ago for a similar
requirement is shown at
http://www.terrypin.dial.pipex.com/Images/555Astable2s.gif
Your own table points out that it isn't exactly 2 Hz. It'll be inaccurate
from the start, and after you tune it, it'll drift.
That's all I was pointing out.
BAJ
He doesn't want 2 Hz. He wants a period of 2 Seconds. That's 500mHz.Your own table points out that it isn't exactly 2 Hz. It'll be
inaccurate
from the start, and after you tune it, it'll drift.